# Abstracted Bibliography

## Abstract

Work on our assessment of the state-of-the-art in ultrasonic spectroscopy was initially directed toward performing a comprehensive literature survey. We began the task by compiling references from our own files and the libraries of the University of Tennessee and Oak Ridge National Laboratory. Several reviews of ultrasonic spectroscopy were found; however, most were either limited in scope or outdated. Searches of computerized data bases were made in an effort to disclose work performed under government contracts, some of which had never been published other than in technical reports. Over 500 pertinent references have been identified, dealing with theoretical work, ultrasonic spectroscopic systems, and the application of spectroscopy to problems in nondestructive evaluation. These citations appear in this report as an abstracted bibliography.

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## References

- 1978–232+.Nabel, E. and Mundry, E., “Evaluation of Echoes in Ultrasonic Testing by Deconvolution,” Mat. Eval., 59–61, 77, Jan., 1978. “This paper is based on what has turned out to be a good tool for ultrasonic echo analysis, namely, linear system theory, and will report some effects of fundamental importance for ultrasonic spectroscopy and deconvolution. In many cases the importance of these effects is not recognized, although they are responsible for most of the differences between experimental results and theory. The paper deals with the improvements in the analysis of echo indications by the calculation of the impulse response of a reflector (deconvolution of ultrasonic echoes). The importance of phase information is emphasized, and the influence of the low frequencies (i.e., the low diffraction orders) on the experimental results is shown. As an example, the result of a simulated convolution will be demonstrated with respect to the theory of replica pulses published by Freedman.” (Author) 11 refs.Google Scholar
- 1977–233.Tamburelli, C., “Use of Ultrasound in Assessing the Susceptibility of Steel to Lamellar Tearing,” NDT International, 3–8, Feb., 1977. “Increasingly, developments in welded constructions means that steel plate with high resistance to lamellar tearing has to be used. An experimental programme has been carried out on 17 C/Mn Fe52D steels, to indicate what features of longitudinal wave transmission ultrasonics may be used in assessing susceptibility to lamellar tearing. A combination of two kinds of evaluation proved promising: the contribution of matrix toughness, measured from the anisotropy of ultrasonic velocity; and the contribution of the amount of inclusions, assessed by ultrasonic attenuation measurements and inclusion counting by ultrasonic reflection. No useful results have been obtained from ultrasonic spectroscopy.” (Author) 7 refs.Google Scholar
- 1978–234+.Budiansky, B. and Rice, J. R., “On the Estimation of a Crack Fracture Parameter by Long-Wavelength Scattering,” J. App. Mech. 45 (2). “Attention is focussed herein on the possibility of estimating the fracture-mechanics parameter k
_{I}= (K_{I})max/σ associated with a flat crack of initially unknown dimensions and orientation by using long-wavelength NDE measurements. Here K_{I}is the mode I stress-intensity factor associated with tension σ normal to the plane of the crack, and “max” denotes the largest value along the crack perimeter. The estimates will be made on the basis of the long wavelength studies by Gubernatis, et al. [1]3, and certain properties of elliptic cracks that are nearly shape invariant.” (Author) 2 refs.Google Scholar - 1975–235+.Canella, G., “The Ultrasonic Field in Water and Steel,” NDT (London), 38–42 (Feb., 1975). “The investigations of the ultrasonic field of transducers used in ndt, had two objects. The first was to compare directly propagation in steel and water. The second was to study the contribution of the beam spread to the attenuation of the echo. The beam spread is considered as a function of the area of the reflector and its distance from the transducer.” (Author) 9 refs.Google Scholar
- 1977–236+.Baboux, J. C., Lakestani, F., Fleischmann, P., and Perdrix, M., “Calibration of Ultrasonic Transmitters,” NDT International. 1977, 135–138 (June, 1977). “A simple experimental method is described which enables the absolute measurement of the acoustic pressure transmitted by a transducer. After a theoretical study of the method used, some experimental results on industrial transducers are given.” (Author) 2 refs.Google Scholar
- 1974–237+.Highmore, P. J., “Nondestructive Testing of Bonded Joints—The Depth Location of Non-Bonds in Multi-Layered Media,” NDT (London), 327–330, Dec, 1974. “In some types of multi-layered structure it is important to detect not only the presence of non-bonds but also to determine their depth locations. This paper describes a simple ndt method, designed especially to meet this requirement, based on the well-known ultrasonic resonance technique.” (Author) 1 ref.Google Scholar
- 1977–238+.Thompson, L. A., “Method of Response Equalization for a Piezoelectric Transducer,” J. Acoust. Soc. Am. 62(6). “A method of using the skirt of a low-pass filter to flatten the projecting response of a piezoelectric transducer is described. An example is given in which the 30 dB response variation of an F-27 standard transducer over the 20–80-kHz frequency range is reduced to 9 dB.” (Author) 1 ref.Google Scholar
- 1972–239+.Myers, G. H., Thumin, A., Feldman, S., deSantis, G. and Lupo, F. J., “A Miniature Pulser-Preamplifier for Ultrasonic Transducers,” Ultrasonics, 87–89 (March, 1972). “In order to avoid difficulties experienced with conventional ultrasonic systems using several feet of shielded cable to connect transducer and electronics, a miniature pulser-preamplifier was developed to fit the transducer holder. Its characteristics proved superior to most devices in common use.” (Author) 3 refs.Google Scholar
- 1977–240+.Hill, J. J., “A Simple Digital Pulse-Shaping Circuit,” Proc. IEEE., 1517 (1977) “A method of generating pulses of prescribed shape is described where binary-coded samples of the pulse are stored in a READ-ONLY memory. The proposed circuit is used to generate pulses having a Gaussian shape.” (Author) 2 refs.Google Scholar
- 1976–241.Cousins, R. R., “The Mathematical Theory for Ultrasonic Spectroscopy,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “A viscoelastic model is proposed to describe the loss of signal of an ultrasonic pulse due to both viscoelastic dissipation and scattering from defects. The material specimen is divided into a number of theoretical layers normal to the direction of travel of pulse, and an analysis of the frequency spectrum of the reflected pulse enables the properties of successive layers to be determined. In the case of laminated material the amplitude of the spectrum is sufficient to determine the depth of delaminated regions, and an experimental example is given.” (Author)Google Scholar
- 1976–242.Adler, L., “Scattering of Broad-Band Ultrasound from Geometrical Shapes Embedded in Metal,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “In order to develop realistic models for flaw characterization in NDE scattering of broadband ultrasonic pulses from various shaped cavities embedded in diffusion-bonded titanium was measured. The frequency and angular distribution of the scattered energy were analyzed and compared with two existing theories: (1) Keller’s geometrical theory of diffraction for the region ka ≧ 1, and (2) Bom’s approximation for the region ka ≦ 1.” (Author)Google Scholar
- 1976–243.Haines, N. F., “Deconvolution in Ultrasonic Spectroscopy,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “Ultrasonic spectroscopy techniques have been used in CEGB Nuclear reactors since 1974 to make measurements of corrosion layers on inaccessible steel surfaces. As from 1977 two of the boards regions will have their own spectroscopy systems with personnel trained to make these measurements on an operational basis. Research work at Berkeley Nuclear Laboratories is continuing into possible other areas of application. During the past 18 months theoretical work and more recently experimental work has demonstrated where spectroscopy techniques may be of use in understanding the reflection of pulses from real defects. The theoretical model developed can predict the reflected waveform and hence peak amplitude as a function of size, shape, orientation and surface roughness of a reflector. The underlying theme of the talk will be the relationship between the time domain and frequency domain. In some cases one domain may give greater physical insight into the system being considered than the other. In particular the reflection from surfaces are perhaps better understood in the time domain and hence the mathematical techniques of convolution and deconvolution become important.” (Author)Google Scholar
- 1976–244.Markham, M. F., “Polymeric and Composite Materials,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “An ultrasonic pulse transmission technique using a spectrum analyzer is described for studying secondary relaxation in polymers. Application to epoxide resins show that the technique yields the dynamic mechanical properties over a wide ultrasonic frequency band. A
*y*relaxation is located, and its behaviour under different cure conditions is investigated. A long term aging effect is also noticed, the study of which could lead to useful information regarding the molecular processes involved at various stages of cure.” (Author)Google Scholar - 1976–245.Lloyd, E. A., “Predictive Modeling of Ultrasonic Responses,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “In testing of structures fabricated from welded plate sections it is required to distinguish between signals returned from a weld bead of uncertain geometry and an equally variable defect echo. In order to understand better the factors governing the visibility of defects in this situation, a computer based modelling technique has been developed with which it is possible to vary the skip distance, probe angle, aperture and frequency response of a synthetic transducer. Whereas in the time-domain, the visibility of a defect will depend largely on the relative size and position of the defect response to the signal generated by the associated weld bead, no such obvious restriction need apply when the dual signal is examined in the frequency domain. There, the choice exists for examining the relative contributions of the defect and weld-bead over the whole or any part of the spectral “window” available for testing. It is for this reason that facilities have been built into the model so that both time-domain and frequency domain representations of a weld-bead associated defect signal can be synthesized. Results will be discussed. As a further test of the validity of the model, a short pulse shear wave transducer was used to interrogate slots of various depths milled over a flat plate. The features predicted are readily discernible.” (Author)Google Scholar
- 1976–246.Quentin, G., “Progress Towards an Ultrasonic Characterization of Rough Surfaces,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “New non-contact methods are described which lead to quite precise estimates of the r.m.s. roughness k of randomly rough surfaces as well as to a separation of periodic surface defects from random roughness. For k < 25 μm accuracy is of the order of ± lμm while for very rough surfaces with h > 50μm accuracy is ± 3μm. Some process has also been made in the measurement of the autocorrelation length.” (Author)Google Scholar
- 1976–247.Nabel, E., “The Importance of Phase for Ultrasonic Spectroscopy and Deconvolution,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “Much work has been done during recent years in the field of ultrasonic spectroscopy. Due to the fact that in most cases only swept frequency receivers were used for spectrum analysis which do not yield any phase information, phase spectrum was often regarded as being of no value. During the research work described in this paper spectrum analysis by means of a swept frequency receiver was replaced by calculating the complex spectrum that means amplitude and phase spectrum with a minicomputer. It became evident that the phase spectrum cannot be regarded separately from the amplitude spectrum. Amplitude and phase spectrum must be considered to be one unique set of data. Only that allows correct deconvolution, and makes it possible to calculate the impulse response of a reflector by inverse Fourier transform. The paper will describe some model experiments in an immersion tank and on a steel specimen, and that it is possible to describe the used reflectors easily by using a deconvolution technique and calculating the impulse response. The effects caused by neglecting phase information will be demonstrated with simulated and natural data.” (Author)Google Scholar
- 1976–248.Lepper, R. D., Decker, D., Trier, H. G., and Reuter, R., “Attempts to Characterize Tissues Using Spectroscopy,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “The paper deals mainly with the practical problems of implementing ultrasonic spectroscopy in the field of tissue differentiation. Firstly, the limitations of the authors1 experimental set-up of 1970 – 74 are discussed. A new set-up now gives considerable improvements, notably on-line digitization and less RF noise. Results are given of in-vitro experiments which reveal the difficulties of using the transfer function of tissue as well as experimental difficulties with highly damped transducers. A calibration method is proposed to overcome these difficulties.” (Author)Google Scholar
- 1976–249.Gore, J. C., and Leeman, S., “Cardiac Tissue Characterization by Ultrasonic Spectroscopy,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “An analysis of ultrasound scattering from tissues shows that the spectral content of the backscattered sound contains useful information about tissue density fluctuations. Such an analysis can be used to characterize tissues but it is shown that the information is limited by the nature of the interrogating sound pulse. When the echoes from heart wall are analyzed it is demonstrated that their spectra reveal information about the contractile state of the cardiac muscle. The extension of this method to the recognition of myocardial disease is presently being attempted and the utility of such information is discussed.” (Author)Google Scholar
- 1976–250.Nicholas, D. and Hill, C. R., “A Spectral Evaluation of Ultrasonic Backscattering from Human Tissues,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “A number of human soft tissues exhibit structural features, and corresponding patterns of acoustic impedance variation, with characteristic spacings of the order of a millimeter. Bulk scattering from such tissues in the megahertz frequency region is thus diffractive in nature, exhibiting marked orientation dependence and a complex dependence on frequency. A series of investigations that have been carried out on these phenomena will be reported and their potential interest for in vivo tissue characterization will be discussed.” (Author)Google Scholar
- 1969–251+.Truell, R., Elbaum, C., and Chick, B. B., Ultrasonic Methods in Solid State Physics, Academic Press, New York (1969), 464 pp, 335 refs. This book contains chapters dealing with (1) propagation of stress waves in solids, (2) measurement of attenuation and velocity by pulse methods and (3) causes of losses and associated velocity changes. A section is included on the “specific application of the spectrum analyzer: factors affecting the spectrum.” The appendices contain diagrams of automated velocity and attenuation measurement systems.Google Scholar
- 1978–252.Davis, M. C., “Coal Slurry Diagnostics by Ultrasound Transmission,” J. Acoust. Soc. Am. 64 (2), 406–410. “Several application of ultrasonic detectors are suggested for monitoring coal water slurries in coal conversion processes. These include mass flow, particle size, and temperature. Modeling of transmission losses include viscous and thermal transport processes as well as multiscattering effects. Simple monitoring of sound attenuation versus frequency yields a unique dependence from which the value of characteristic parameters may be deduced, all from a single transmitter-receiver pair.” (Author) 8 refs.Google Scholar
- 1978–253.Ting, C. S. and Sachse, W., “Measurement of Ultrasonic Dispersion by Phase Comparison of Continuous Harmonic Waves,” J. Acoust. Soc. Am. 64 (2), 852–857. “The method of phase comparison of continuous waves is applied to determine the dispersion relation, phase, and group velocities as a function of dispersive materials. A combination of the variable frequency method and the variable path-length method is found necessary to eliminate any uncertainty in the dispersion relation determination. Experiments are performed on specimens of various thickness. A constraint equation can be derived since the dispersion relation is unique and independent of the specimen thickness. This equation provides a procedure for determining the absolute number of wavelengths in the specimen. Measurements in unidirectional, fiber-reinforced boron-epoxy specimens show good agreement with results reported previously.” (Author) 14 refs.Google Scholar
- 1978–254.Bray, D. E., Egle, D. M. and Reiter, L., “Rayleigh Wave Dispersion in the Cold-Worked Layer of Used Railroad Rail,” J. Acoust. Soc. Am. 64 (2), 845–851. “The first shear mode (Sezawa mode) and the fundamental Rayleigh mode have been identified as they propagated through the work-hardened layer on the top surface of used, steel railroad rail. Longitudinal wave velocities and densities are very nearly equal for the work-hardened layer and the subadjacent layer. The ratio of shear wave velocity in the upper layer to that in the subadjacent layer is near to 0.95. Experimental data obtained at several frequencies (0.5–2.0 MHz) showed good agreement with expected velocities for a layer thickness ranging from 3 to 5 mm.” (Author) 13 refs.Google Scholar
- 1970–255.Meyer, H. J., “Inspection of Grey Iron Castings by Ultrasonic Attenuation,” Non-Destruc. Test. (London), 99–104, April 1970. “Ultrasonic pulses of definite frequency and wavelength undergo a varying degree of scatter depending upon the size and quantity of graphite flakes in grey cast iron. The amount of sound energy left after a sound beam has passed a given cross-section provides, therefore, a measure of the structure and content of the graphite and consequently, the physical strength of the cross-section.” (Author) 10 refs.Google Scholar
- 1973–256+.Chang, F. H., Couchman, J. C. and Yee, B. G. W., “Transmission Frequency Spectra of Ultrasonic Waves through Multi-Layer Media,” Proc. 1973 IEEE Ultrasonic Symp. “The frequency spectrum of ultrasonic plane waves transmitted through a multi-layered laminate structure at normal incidence was analyzed to study the amplitude distribution of the frequency components. In supporting the theoretical calculations, the wave equation was solved to evaluate the displacement field with the appropriate boundary conditions in a six-region laminate. Cavity resonation of the plane waves in the layers produced peaks in the transmission frequency spectrum. Experiments were conducted using a pair of broad-band acoustical transducers transmitting a pulsed ultrasound centered at 5 MHz through multi-layer adhesive-bonded aluminum plates with different plate thicknesses. Resonant peaks in the experimental frequency spectra were compared with those theoretically calculated for regions of good bond and regions of disbond. Applications of this technique to nondestructive testing of bonded structures are described.” (Authors) 9 refs.Google Scholar
- 1978–257+.Hill, J. J., “Digital Generation of a Nonlinear Time-Base,” IEEE Trans. Instrum. Msmt., IM-27 (3), 298–300. “A Method of generating nonlinear time-bases is described. The approximation may be either step or piecewise linear and involves using a READ-ONLY memory as a look-up table to store digitally the shape of the required function. The case of a logarithmic time-base is considered in detail.” (Author) 4 refs.”Google Scholar
- 1978–258+.Khuri-Yakub, B. T. and Kino, G. S., “A New Technique for Excitation of Surface and Shear Acoustic Waves on Nonpiezoelectric Materials,” Appl. Phys. Lett., 32 (9), 513–514 (May 1978). “An interdigital transducer deposited on a piezoelectric substrate has been used to excite SAW on nonpiezoelectric materials by using a fluid couplant« The piezoelectric substrate is held at an angle to the nonpiezoelectric material so as to match the tangential k vectors of the surface waves. Experiments have been carried out with a LiNbO
_{3}piezoelectric substrate and a ceramic such as SiC or Si_{3}N_{4}with a fluid couplant. At a center frequency of 100 MHz, the estimated conversion efficiency of the surface wave from the piezoelectric to the nonpiezoelectric material is -3.5 dB. The results compare favorably with a normal mode coupling theory we have developed which predicts-2.7 dB efficiency.” (Authors) 8 refs.Google Scholar - 1976–259+.Lakin, K. M. and Fedotowsky, A., “Characterization of NDE Transducers and Scattering Surfaces Using Phase and Amplitude Measurements of Ultrasonic Field Patterns,” IEEE Trans. Son. Ultrason., SU-23 (5), 317–322. “The characterization of transducers for quantitative NDE applications requires that the radiation pattern, conversion efficiency, and bandwidth be accurately determined. These quantities may, in principle, be determined if the transducer’s construction and constituent parts are independently known. However, most often the internal details of the transducer are unknown and subject to statistical variations and aging. A measurement technique and system for characterizing transducers based upon external measurements is described, which does not rely upon knowledge of the transducer’s construction.” (Author) 11 refs.Google Scholar
- 1978–260+.Fraser, J., Khuri-Yakub, B. T. and Kino, G. S., “The Design of Efficient Broadband Wedge Transducers,” Appl. Phys. Lett. 32 (11), 698–700 (June 1978). A simple coupled-mode theory has been developed for acoustic-surface-wave wedge transducers. Surface-wave transducers have been fabricated to operate on aluminum using water as the wedge material. The measured efficiency was 68% at 2.75 MHz, the theoretical value being 81%. Transducers have also been fabricated to operate on glass with a rubbery solid, RTV 615, as the wedge material. The experimental and theoretical efficiencies of this transducers at 3.2 MHz were 35 and 50%, respectively. The surface-wave leakage coefficient of RTV 615 on glass has been measured and found to be in excellent agreement with theory.” (Author) 5 refs.Google Scholar
- 1966–261.vander Pauw, L. J., “The Planar Transducers — A New Type of Transducer for Exciting Longitudinal Acoustic Waves,” Appl. Phys. Lett. 9 (3), 129–131 (August 1966). “We have constructed a new type of transducer for exciting longitudinal acoustic waves. It has only one interface, for which reason we shall call it a “planar” transducer. The planar transducer has comb-shaped electrodes which can be applied with a standard photo-mask technique. The frequency characteristics of the planar transducer turns out to be favorable compared with the frequency characteristic of the conventional transducer. We shall first mention the essential characteristics of the conventional transducer and then compare these with the characteristics of the planar transducer.” (Author). It is shown that the planar transducer has a wide-band frequency response, although the overall response seems to be about 10 dB lower than that of a plate transducer. 2 refs.Google Scholar
- 1978–262+.Rhyne, T. L., “An Improved Interpretation of Mason’s Model for Piezoelectric Plate Transducers,” IEEE Trans. Son. Ultrason. SU-25 (2), 98–103 (March 1978). “A new interpretation of Mason’s model for a piezoelectric plate transducer is presented. The network model emphasizes a series connection for the two acoustic loads while utilizing lumped impedance elements expressed as functions of the delay operator Z = exp sT. An exact analysis of the plate dynamics permits a simplified resistive model for conditions of light asymmetry in acoustic loading. A simplified resistive structure provides transmission (reception) loss near the half-wave resonance. Air backed front loading is modeled. Finally, RLC lumped component models are provided for evaluation of transducers as lumped element filters.” (Author) 18 refs.Google Scholar
- 1973–263+.Wright, H., “Impulse-Response Function Corresponding to Reflection from a Region of Continuous Impedance Change,” J. Acoust. Soc. Am. 53 (5), 1356–1359 (1973). “Acoustic reflection from a region of continuously varying specific acoustic impedance is characterized, in the linear circuit sense, by a unit reflection impulse-response function R(t). It is shown that in the absence of attenuation and for modest impedance excursions, the impulse-response function corresponding to reflection from a region which has continuously variable impedance along the incident axis is given by R(2t) ≈ (dz/dt)/4z, where z(t) is the impedance profile and t is acoustic travel time.” (Author).Google Scholar
- 1973–264+.Sigelmann, R. A. and Reid, J. M., “Analysis and Measurement of Ultrasound Backscattering from an Ensemble of Scatterers Excited by Sine-Wave Bursts,” J. Acoust. Soc. Am. 53 (5), 1351–1355 (1973). “This paper develops a practical approximation for the backscattering of periodic bursts of sine waves by a volume of randomly distributed scatterers. The approximation is applied to the measurement of a ‘volumetric backscattering cross section,’ using a substitution method in which the rms value of the gated backscattered signal is compared with the rms value of a wave reflected from a target of known coefficient of reflection. It is shown that the signal backscattered from the ensemble depends on the attenuation of the wave in the volume and upon the burst and gate lengths. An equation to obtain the volumetric backscattering cross section from experimental data is derived.” (Author) 6 refs.Google Scholar
- 1977–265+.Rhyne, T. L., “Radiation Coupling of a Disk to a Plane and Back or a Disk to Disk: An exact Solution,” J. Acoust. Soc. Am. 61 (2), 318–324 (February 1977). “The radiation coupling or coupling by propagating waves is solved for a disk in an infinite baffle to a plane and back or equivalently a disk to a disk both in infinite baffles. The radiation coupling is defined as a linear filter operating between lumped mechanical components which may be incorporated into transducer models. The impulse response of the radiation-coupling filter and the Fourier transfer function for the radiation-coupling filter are solved in closed form. The radiation-coupling gain (loss) is applicable to the correction of experimental data and to the absolute calibration of circular transducers by self-reciprocity measurements.” (Author) 14 refs.Google Scholar
- 1977–266+.Weight, J. P. and Ravenhall, F. W., “An Inexpensive Wideband Recording Facility,” J. Phys. E. (Sci. Instr.) 10 (4), 424–428 (1977). “A series of modifications is described whereby a commercial video tape recorder was adapted for non-TV-format signals. The recorder used had a typical twin-head helical scanning system, with slow-motion and stop-playback capabilities. The signals to be recorded in this case were developed during crack propagation of metal specimens under tension, i.e., stress-wave emissions. These occur at random intervals and are in the frequency range 20 kHz to 2 MHz.” (Author) 3 refs.Google Scholar
- 1977–267+.Harnik, E., “A Broadband Probe for Studies of Acoustic Surface Waves,” J. Phys. E. (Sci. Instr.) 10 (12), 1217–1218 (1977). “An acoustic surface wave probe has been developed for use in broadband non-destructive testing and in seismological modelling. The probe has a bandwidth of about 0.4–4 MHz but the design is suitable for use up to centre frequencies of about 5 MHz. It takes a negligible amount of energy from the ultrasonic beam and appears to reproduce accurately the shape of an ultrasonic pulse. The probe is characterized by simplicity of construction and operation,” (Author) 6 refs.Google Scholar
- 1970–268+.Gericke, O. R., “Theory and NDT Applications of Ultrasonic Pulse-Echo Spectroscopy,” Proc. Symp. on the Future of Ultrasonic Spectroscopy, London, October 1970, Paper #1. The author discusses the use of a pulsed swept-frequency system for ultrasonic spectroscopy. The main advantage is that one is able to produce a flat frequency response with such a device. Unfortunately the time resolution and signal-to-noise ratio are both poor. The use of ultrasonic spectroscopy for examining material micro-structure, assessing severity of defects and investigating the frequency-dependence of ultrasonic beam spreading, is reviewed. Many spectra, produced by the author’s apparatus, illustrate the productive uses of spectroscopy.Google Scholar
- 1970–269+.Lloyd, E. A., “Wide-Band Ultrasonic Techniques,” Proc. Symp. on the Future of Ultrasonic Spectroscopy, London, October 1970, Paper #2. Wide-band ultrasonic techniques are categorized as either measurements of distributed phenomena (grain size, etc.) or detection and classification of discrete targets. Furthermore, the target may be non-penetrable (a void) or penetrable. The signals from the penetrable target, being in general the more complex. Response of the defect is approximated by considering only its main scattering features. Discrete scattering centers result in modulations in the magnitude spectrum. Cepstral processing is discussed as a method for extracting defect-size information from the modulated spectrum. The possibility of compact data presentation as the coefficients in a power series expansion (in frequency) of the material’s transfer function is mentioned. Several novel designs for wide-bandwidth transducers are presented.Google Scholar
- 1970–270+.Aldridge, E. E., “Ultrasonic Spectroscopy at the NDT Centre, Harwell: Progress Report,” Proc. Symp. on the Future of Ultrasonic Spectroscopy, London, October 1970, Paper #3. Work to date at Harwell has centered about the design and construction of spectroscopic instrumentation. The importance of gating circuits, with minimal switching transients, for use with analog spectrum analyzers is noted. Problems of signal pick-up from fast digital circuitry is mentioned. The author notes that if the flaw affects frequency components, which are at the same time attenuated by the material surrounding the defect, information concerning the defect may be difficult to extract.Google Scholar
- 1970–271+.Clipson, W. R., “Ultrasonic Spectroscopy Development for Inclusion Cloud Assessment,” Proc. Symp. on the Future of Ultrasonic Spectroscopy, London, October 1970, Paper #4. Frequently, defects occur as “clouds” of small inclusions. Whereas the size of individual defects may be such as to preclude detection, the cloud is detectable. Although no theoretical work is given, experimental spectral measurements (utilizing a wave analyzer) is presented. Spectral differences in the signals from flat-bottom and side-drilled holes were observed, indicating hope for flaw characterization.Google Scholar
- 1970–272+.Mitchell, R. F., “Wide-Band Acoustic Bulk Wave Transducers,” Proc. Symp. on the Future of Ultrasonic Spectroscopy, London, October 1970, Paper #5. Observation that a CdS thin-film transducer gave a flat frequency response led the author to investigate the properties of a transducer with a piezoelectric constant which varies through its thickness. For certain functional relationships of piezoelectric constant versus distance, the transducer’s response will be broadbanded. An interdigital bulk-wave device and a transducer with a shaped back surface also hold possibilities for wide-band response.Google Scholar
- 1942–273+.Mason, W. P., Electromechanical Transducers and Wave Filters, Van Nostrand Co., Inc., New York (1942).Google Scholar
- 1964–274+.Berlincourt, D. A., Curran, D. R., and Jaffee, H., “Piezoelectric and Piezomagnetic Materials and Their Function in Transducers,” Ch. 3 in Physical Acoustics, Vol. I, Part A (W. P. Mason, ed.), Academic Press, New York (1964).Google Scholar
- 1978–275+.Fox, M. D. and Donnelly, J. F., “Simplified Method for Determining Piezoelectric Constants for Thickness Mode Transducers,” J. Acoust.Soc. Am. 64 (5), 1261–1265. “A procedure is described for obtaining the stress constant e
_{33}for an arbitrary piezoelectric transducer operating in the thickness mode. A closed-form solution is developed which uses measurements of the electrical impedance of the transducer as input. Verification of the calculated parameters is accomplished by incorporating them into a computer model of the transducer. A discussion of various methods of obtaining the clamped capacitance C_{0}is included as well as a calculation of an equivalent resistance to represent losses in the ceramic. Numerical examples are presented.Google Scholar - 1972–276+.Papadakis, E. P., “Ultrasonic Diffraction Loss and Phase Change for Broad-Band Pulses,” J. Acoust. Soc. Am. 52 (3), 847–849. “The effective diffraction loss and phase change in the field of broad-band transducers is computed in terms of the normalized distance S
_{c}= zλ_{c}/a^{2}at the center frequency of the pulse. Diffraction corrections for attenuation and velocity are explained, and their limitations stated for broad-band pulses. It is shown that the corrections are functions of bandwidth as well as of S_{c}.” (Author)Google Scholar - 1964–277.Carome, E. F., Parks, P. E., and Mraz, S. J., “Propagation of Acoustic Transients in Water,” J. Acoust. Soc. Am. 36, 946–952. “A technique is described for investigating the propagation of acoustic transients in liquids. Thick piezoelectric plates are employed as acoustic sources and detectors. The results of recent theoretical works on the transient response of such elements are extended to determine the relationships between the time profiles of the voltage applied to the source, the stress wave in the liquid, and the output voltage of the detector. Effects of transient processes in the field of a piston source also are considered. Results are presented of an experimental study of the propagation in water of low-amplitude pressure steps and impulses as narrow as 0.05 μsec. The data are strongly dependent on the parameters of the source-detector configuration. This limits the range of applicability of the technique, but its usefulness for studies of absorbing liquids is indicated.”Google Scholar
- 1970–278.Freedman, A., “Sound Field of Plane or Gently Curved Pulsed Radiators,” J. Acoust. Soc. Am. 48, 221–227. “When a single pulse is applied to a plane radiator in a large rigid baffle or to a convexly curved baffled radiator having dimensions and radii of curvature large compared with the relevant wavelengths, the pressure at a field point is shown theoretically to consist, generally, of a sequence of pulses, each of which is, approximately, a scaled replica of the applied pulse. The number of pulses and their relative size and spacing are functions of position of the field point. In the direction of the main beam, if the radiating surface is plane, these pulses are not resolved and a single nearly undistorted pulse is obtained. A form of reciprocity is shown to exist between the structure of the acoustic signal at a point in the field of a pulsed transducer when transmitting and the structure of the electrical signal when the same transducer receives an acoustic pulse. Simple relationships are presented between the formulas for pulsed radiation, reception, and backscattering from a plane surface.” (Author)Google Scholar
- 1976–279+.Kazhis, R. I. and Lukoshevichyus, A. I., “Wideband Piezoelectric Transducers with an Inhomogeneous Electric Field,” Sov. Phys. Acoust. 22, 167–168. “The bandwidth of piezoelectric transducers is mainly limited by the presence of two sources of ultrasound near the faces of the piezoelectric element and multiple reflections of the generated ultrasonic waves in the transducer. ... We have investigated piezoceramic transducers with an inhomogeneous electric field, for which the distribution of the force lines is determined by a special placement of the working electrodes relative to the crystallographic axes of the piezoelectric.” (Author)Google Scholar
- 1970–280.Stephanishen, P. R., “Transient Radiation from Pistons in an Infinite Baffle,” J. Acoust. Soc. Am. 49, 1629–1638. “An approach is presented to compute the near- and farfield transient radiation resulting from a specified velocity motion of a piston or array in a rigid infinite baffle. The approach, which is based on a Green’s function development, utilizes a transformation of coordinates to simplify the evaluation of the resultant surface integrals. A simple expression is developed for an impulse response function, which is the time-dependent velocity potential at a spatial point resulting from an impulse velocity of a piston of any shape. The time-dependent velocity potential and pressure for any piston velocity motion may then be computed by a convolution of the piston velocity with the appropriate impulse response. The response of an array may be computed using superposition. Several examples illustrating the usefulness of the approach are presented. The farfield time-dependent radiation from a rectangular piston is discussed for both continuous and pulsed velocity conditions. For a pulsed velocity of time duration T it is shown that the pressure at several of the field points can consist of two separate pulses of the same duration, when T is less than the travel time across the piston.” (Author)Google Scholar
- 1974–281.Robinson, D. E., Lees, S., and Bess, L., “Near Field Transient Radiation Patterns for Circular Pistons,” IEEE Trans. Acoust. Speech Sig. Proc. 22 (6), 395–403. “The exact impulse response of field parameters for any field point on or off axis for the case where a circular disc radiator face is subjected to a displacement step corresponding to a velocity impulse is reviewed. By convolution, the transient field pattern for any arbitrary motion of the disc can be obtained. The exact response for a half-sine monopulse is computed. An approximate representation of the transient pressure response to the velocity impulse input at the disc is derived, and it is shown to correspond to the replica pulses described previously. The regions of validity of the approximation are quite limited and the replica pulses are displaced in time from the positions formerly attributable to them. The displaced replica approximation is applied to an examination of the structure of the near field for continuous sinusoidal excitation and a plot of positions of extrema is produced. It is shown that this approximation gives good agreement with the exact values and is superior to the previous published approach in this regard. For short sinusoidal pulses the effect of pulse length on the field pattern, and of field point on the time history of a transient wave are shown. When the excitation is a short sinusoidal pulse the effect of the pulse length and field point position on the field pattern and wave shape are demonstrated.” (Author).Google Scholar
- 1966–282.Kossoff, G., “The Effects of Backing and Matching on the Performance of Piezoelectric Ceramic Transducers,” IEEE Trans. Son. Ultrason. SU-13 (1), 20–30. “The effects of backing and matching on the performance of transmitting and receiving PZT7A transducers working into a water load are analyzed. Although backing widens the bandwidth, it also increases the transmission loss, and more efficient and wider bandwidth transducers are obtained by quarter-wave matching the transducer to the water load. By quarter-wave matching the transducer to low impedance absorbing backings, reflected high impedance absorbing backings may be obtained; and very wide bandwidth and efficient transducers are obtained by quarter-wave matching both to the backing and to the load. In pulse detection applications, the pulse width of these transducers has been found to be nearly independent of such increases in bandwidth. The explanation for this effect and a procedure for determining the approximate echo pulse waveform is presented.” (Author)Google Scholar
- 1972–283.Meeker, T. R., “Thickness Mode Piezoelectric Transducers,” Ultrasonics, 26–36 (January 1972). “This paper is a tutorial review of the theory of the simple thickness mode piezoelectric transducer. The usual differential equations and constitutive relations are used to obtain general impedance equations for the transducer with arbitrary boundary conditions. In the derivations, special attention is given to showing what basic assumptions are made, and which material constants must be used in the equations. As usual, the thickness mode theory is only valid if no quantities depend on the lateral co-ordinates of the plate. It is shown that certain elastic and piezoelectric constants must be zero in the plate co-ordinate system for the simple thickness mode theory to be valid for the transducer. Four geometrical and material variables, and three boundary conditions completely determine the transfer and impedance properties of the transducer. Exact expressions are given for the electrical impedance of the simple thickness mode resonator with free surfaces, and for three electrical properties of a bonded and backed thickness mode transducer (namely, the electrical impedance at low frequency, and the electrical impedance and transfer loss at the halfwave frequency). The transfer loss is 3.3 dB for an unbacked, untuned, and acoustically matched transducer with no series electrical resistance and a piezoelectric coupling factor of 0.5.” (Author)Google Scholar
- 1969–284.Sittig, K. E., “Effects of Bonding and Electrode Layers on the Transmission Parameters of Piezoelectric Transducers Used in Ultrasonic Digital Delay Lines,” IEEE Trans. Son. Ultrason. SU-16 (1), 2–10. “In ultrasonic delay lines with thickness-driven piezoelectric transducers, it is necessary to have electrode and, possibly, bonding layers in the sound transmission path. If these layers have characteristic impedances that are substantially different from those of the piezoelectric transducer and the delay medium, they act as mismatched transmission line sections between the transducer and its load, and transform the normally real load impedance into a complex one. The resulting shifted and deformed response curves are computed for a large number of layer parameters by means of Mason’s equivalent circuit. From these plots, information as to permissible layer thickness, etc., may be obtained and used in the design procedure of ultrasonic delay lines. In digital delay lines, where linear phase response is a design requirement, any intermediate layers should be as thin as possible or be closely matched to the delay medium in order to avoid fast ripples in the frequency response, which would give rise to side lobes far away from the main signal in the time domain.” (Author)Google Scholar
- 1967–285.Sittig, K. E., “Transmission Parameters of Thickness Driven Piezoelectric Transducers Arranged in Multilayer Configurations,” IEEE Trans. Son. Ultrason. SU-14, 167–174. “The individual transducers of an ultrasonic delay line may consist of a multiplicity of piezoelectrically active layers electrically connected in series, parallel, or grouped in series-parallel combinations interspersed with electrically conductive or nonconductive layers of different characteristic acoustic impedances. The stack of transducer layers may be loaded by an absorptive or reactive backing and coupled to the delay medium through bonding and matching layers. The transmission parameters for such configurations are written in a form well suited to digital computation. Inspection of numerical results reveals effects which may be qualitatively understood by visualizing separately the effects due to the mechanical resonances of the layer assembly and those due to the arrangement of piezoelectric material with respect to the stress distribution within the stack. The examples given indicate that transducers consisting of alternately poled stacked A/2 layers of a low coupling factor material such as CdS give an insertion loss improvement at the cost of bandwidth reduction little different from that obtained with narrow-band tuned terminations. For high coupling factor layers, no significant improvement is obtainable.” (Author)Google Scholar
- 1971–286.Mattiat, O. E. (editor), Ultrasonic Transducer Materials, Plenum, New York.Google Scholar
- 1975–287.Martin, R. W. and Sigelmann, R. A., “Force and Electrical Thevenin Equivalent Circuits and Simulations for Thickness Mode Piezoelectric Transducers,” J. Acoust. Soc. Am. 58 (2), 475–489. “A simple model is reported for thickness-mode piezoelectric elements used as ultrasonic transducers in measurement systems. The model represents the excitation system and transducer as a Thevenin mechanical equivalent for the transmitting mode and a Thevenin electrical equivalent for the receiving mode. Computer programs based on the model have been developed, and computer simulations to study the effects of backing materials, element areas, and excitation sources are reported. The nature in which the source impedance alters the Thevenin mechanical output impedance and its importance in determining peak transmission frequency and in computing acoustic coating layers for matching are found. A total transfer improvement of 28 dB was shown for epoxy-backed elements radiating into fluid with the transducer used as both transmitter and receiver by using high values of source and load impedances in contrast to low values. The model was found to agree closely with experimental data of a 2.7-MHz transducer.” (Author)Google Scholar
- 1973–288+.Legros, D. and Lewiner, J., “Electrostatic Ultrasonic Transducers and Their Utilization with Foil Electrets,” J. Acoust. Soc. Am. 53 (6), 1663–1672. “Electrostatic ultrasonic transducers are very attractive when considered from the point of view of simplicity. They are constituted by a condenser, the ultrasonic wave being directly excited on the electrodes. These transducers are currently used at low frequencies (microphones) and sometimes at higher frequencies (up to a few megahertz). At higher frequencies the bias voltage applied across the condenser has to be quite large and electrification of the central dielectric layer can appear. This paper describes such effects and presents the experimental conditions allowing the transducer to operate. The electrification of the dielectric layer is studied and the problems related to the conservation of the deposited charges are considered for Mylar and polypropylene foils of about 10-μ thickness. In the present work the ultrasonic waves generated or received by these transducers have frequencies ranging from 10 to 200 MHz.” (Author)Google Scholar
- 1973–289+.Sessler, G. M. and West, J. E., “Electret Transducers: A Review,” J. Acoust. Soc. Am. 53 (6), 1589–1600. “A review of the history, design, performance, and application of electret transducers is presented. Particular emphasis is placed on foil-electret transducers incorporating a thin-film electret made of Teflon or related materials. Such transducers have excellent frequency response, low distortion, small vibration sensitivity, and have been used over a frequency range extending from 10–3 to 2 × 108 Hz. They can be made in a variety of shapes over, a large range of sizes and are generally not affected by adverse environmental conditions. More than 10 million electret transducers are being manufactured annually as microphones with various directivity patterns for use in amateur and studio applications, tape recorders, sound-measuring instruments, telephone-operators’ headsets, hearing aids, and acoustic-graphic tablets, and as transducers in earphones and phonograph cartridges. Electret transducers are also used for experimental and research applications in such widely different fields as gas analysis, opto-acoustic spectroscopy, aeronautics, atmospheric studies, telephony, ultrasonics, acoustic holography, data transmission, and leak detection in space stations.” (Author)Google Scholar
- 1962–290+.Freedman, A., “A Mechanism of Acoustic Echo Formation,” Acustica 12, 10–21. “Using a method of analysis analogous to that of physical optics, the direct backscattering of small amplitude acoustic waves from a rigid body, immersed in an ideal fluid medium is re-examined. The incident radiation is a pulse of general type, and at long ranges, no restrictions are imposed on the directivity patterns of the transmitting and receiving transducers. Clarification of the echo-formation mechanism applicable at small wavelengths is obtained. The echo is shown to be composed of a number of discrete pulses, each a replica of the transmission pulse, and hence termed an ‘image pulse.’ An image pulse is generated whenever there is a discontinuity with respect to range, r, in dnW(r)/drn, where W(r) is the solid angle subtended at the transducers by that part of the scattering body within range r. n may be zero or any positive integer. It is shown that four types of echo envelope arise from varying degrees of overlap of these image pulses. The combination of ‘image pulse’ and ‘creeping wave’ mechanisms is believed to account for the main scattering phenomena from rigid convex bodies, the former mechanism being paramount outside the shadow region at small wavelengths, the latter mechanism predominating at large wavelengths.” (Author) 7 refs.Google Scholar
- 1960–291.Filipczynski, L., “Transients and the Equivalent Electrical Circuit of a Piezoelectric Transducer,” Acustica 10, 149. “The subject of the present paper is an X-cut quartz transducer, in which one-dimensional mechanical vibrations are discussed. Starting with piezoelectric equations in terms of the electrical enthalpy, transients of the transducer, frequency-response characteristics and the input impedance are analyzed. The results of experiments confirm the described mechanism of the vibrations in the transducer, as well as the frequency-response characteristics. On the basis of the results obtained, an equivalent electrical circuit of the transducer has been constructed in terms of a transmission line. The given circuit is valid for steady states and for transients as well.” (Author)Google Scholar
- 1974–292.Beaver, W. L., “Sonic Nearfields of Pulsed Piston Radiators,” J. Acoust. Soc. Am. 56, 1043–1048. “The formation of sonic pulses in the nearfield region of a pulsed piston radiator has been investigated by similation on a digital computer. The results give insight into the sonic radiation process, showing the formation of pulses that replicate the piston motion, with trailing disturbances which originate from the rim. A comparison is made between pulsed and CW beam profiles, showing that there is little difference for moderate pulse lengths.” (Author)Google Scholar
- 1975–293+.Tabuchi, D., Inoue, N., Okuwa, T., and Ohno, K., “Ultrasonic Spectroscopy and Automatic Ultrasonic Spectrometer,” Acustica 32, 236–243. “An automatic recording ultrasonic spectrometer has been constructed in order to measure and record the frequency spectra of ultrasonic absorption and velocity. For the measurement of absorption an ultrasonic pulse echo method is used, and an ultrasonic pulse circulation method is applied for the measurement of velocity. The data of absorption and velocity are punched on a tape, and typed. If the tape is put into a digital computer, the ultrasonic spectra and the characteristic values are computed, punched on a tape, and typed. When the tape is put into the ultrasonic spectrometer, the ultrasonic spectra of absorption and velocity are recorded by a digital plotter. The process is completely automated by a method of sequence control.” (Author) 6 refs.Google Scholar
- 1971–294+.Papadakis, E. P. and Fowler, K. A., “Broadband Transducers: Radiation Field and Selected Applications,” J. Acoust. Soc. Am. 50 (3), 729–745. “In many applications, broad-band ultrasonic transducers capable of producing short video pulses are required. Previously, plane-wave analysis with equivalent circuits has proven successful in predicting pulse shape in the time and frequency domains. The present approach is to recognize that piston sources radiate nonplanar waves, and that the frequency spectrum of a broad-band piston source can be measured experimentally. With the spectrum as a weighing function for the field profiles of a monofrequency piston source, a superposition is performed to find the pressure and phase profiles in the radiation field of a broad-band transducer. Experimental measurements are presented that take advantage of the broad-band pulse technique combined with spectrum analysis. These include thickness gauging of thin materials and interface layers, and relative viscosity measurements.” (Author)Google Scholar
- 1971–295+.Papadakis, E. P., “Effects of Input Amplitude Profile Upon Diffraction Loss and Phase Change in a Pulse-Echo System,” J. Acoust. Soc. Am. 49 (1), 166–168. “The particle velocity profile V(p) across the face of a transmitting transducer is shown to have large effects upon the diffraction loss and phase change in the ultrasonic field of the transducer. Various functions V(p), monotonic decreasing from the center to the rim of a circular transducer, were employed. The pulse-echo response of the transducer was calculated by numerical integration on an electronic computer. It was found that the functions V(p) chosen caused the diffraction-loss and phase-change curves to be smoother than in the piston case and caused the respective peaks and plateaus to shift with distance in the Fresnel region.” (Author)Google Scholar
- 1960–296+.Brekhovskikh, L. M., Waves in Layered Media, Academic Press, New York (translated from the Russian by D. Lieberman and edited by R. T. Beyer).Google Scholar
- 1963–297+.Redwood, M., “A Study of Waveforms in the Generation and Detection of Short Ultrasonic Pulses,” Appl. Mat, Res. 2, 76–84. “Investigations of the properties of materials frequently make use of short ultrasonic pulses consisting of from one to about ten oscillations which are roughly sinusoidal in shape. The ultrasonic signal is usually generated by applying an electrical signal to a piezoelectric transducer. After passing through the material under investigation it is detected by using a second piezoelectric transducer. The nature of the electrical waveforms observed in such experimental systems and their relation to the ultrasonic signal is frequently not well understood, as they are dependent on a complex combination of circumstances involving (1) the thickness of the transducers, (2) the acoustic impedances of the materials in contact with both faces of each transducer, and (3) the nature of the electrical resistance into which the receiving transducer feeds. Sometimes the pulse shape is also considerably affected by the nature of the material under investigation, particularly if this material is highly absorbent. Lack of understanding of the change in shape of the waveform which can be produced, particularly by the receiving transducer, frequently leads to misconceptions concerning the actual shape of the ultrasonic pulse and its frequency spectrum. This may also lead to considerable errors in estimates of its velocity and attenuation. The generation and detection of ultrasonic pulses by using piezoelectric transducers are treated here in some detail. Methods of predicting the various ultrasonic and electrical waveforms are developed and illustrated by application to a particular system designed for the measurement of velocity in small samples of material and hence using as short an ultrasonic pulse as possible.” (Author) 3 refs.Google Scholar
- 1978–298+.Simpson, W. A., Jr., “A Microcomputer-Controlled Ultrasonic Data Acquisition System,” Oak Ridge National Laboratory Tech. Memo 0RNL/TM6531. “The large volume of ultrasonic data generated by computer-aided test procedures has necessitated the development of a mobile, high-speed data acquisition and storage system. This approach offers the decided advantage of on-site data collection and remote data processing. It also utilizes standard, commercially available ultrasonic instrumentation. This system is controlled by an Intel 8080A microprocessor. The MCS80-SDK microcomputer board was chosen, and magnetic tape is used as the storage medium. A detailed description is provided of both the hardware and software developed to interface the magnetic tape storage subsystem to Biomation 8100 and Biomation 805 waveform recorders. A boxcar integrator acquisition system is also described for use when signal averaging becomes necessary. Both assembly language and machine language listings are provided for the software.” (Author)Google Scholar
- 1976–299.Robinson, D. E. and Williams, B. G., “Digital Acquisition and Interactive Processing of Ultrasonic Echoes,” Ultrasound in Med. and Biol. 2, 199–212. “The requirements for an interactive digital signal processing system for ultrasonic pulse-echo signals are discussed. A system based on an Interdata Model 80 mini-computer and micro-processor interface is described. The system is capable of acquiring ultrasonic data at a sampling rate of 6 MHz. Ultrasonic B-mode data may be acquired in Line Mode, when echo waveform data and transducer position and orientation are stored, or in Section Mode when the data is converted directly into picture form in memory in the same way that a standard echogram is formed on the screen of an oscilloscope. In each case the data for single complete high resolution echogram may be acquired in less than 15 sec. It is shown that the 6 MHz sampling rate is sufficient to faithfully preserve the echo waveshape of a 2 MHz system independently of the relation to the phase of the sampling. Also shown is a cross-sectional echogram of the pregnant uterus, and its digital representation with a raster density of 80 × 100 and 160 × 200 picture elements. The computer is programmed with an interactive program to allow ultrasonic signals to be acquired, stored, processed and examined with the convenience of a desk calculator. Sample operations are illustrated including data interpolation, spectrum analysis, filtering and complex signal deconvolution. The ability of deconvolution techniques to resolve targets separated by less than one wavelength in depth is demonstrated. Possibilities of further processing techniques are outlined.” (Author) 20 refs.Google Scholar
- 1978–300.Elsley, R. K., “Accurate Ultrasonic Measurements with the Biomation 8100 Transient Recorder,” Proc. First Intl. Symp. on Ultrason. Mat. Characterization, June 1978. “The Biomation 8100 Transient Recorder performs 8-bit analog-to-digital (A/D) conversions at a 100 MHz sample rate and is widely used for data acquisition of high frequency ultrasonic signals. Due to the nature of the A/D method used, the accuracy is substantially less than 8-bits under some conditions, particularly at high frequencies. The errors which occur are found to be partially random and partially systematic (called “preferred states” by the manufacturer). The accuracy which can be obtained depends not only on the signal which is being acquired, but also on what features of that signal the experimenter is interested in measuring. By using signal averaging and offset variation, dynamic ranges in excess of 70 dB (12-bits) have been obtained, and subtle but important features in the signals being analyzed have been thereby measured.” (Author) 1 ref.Google Scholar
- 1956–301.Ying, C. F. and Truell, Rohn, “Scattering of a Plane Longitudinal Wave by a Spherical Obstacle in an Isotropically Elastic Solid,” J. Appl. Phys. 27, 1086–1097 (1956). The first consideration of the scattering of an acoustic wave propagating in a solid.Google Scholar
- 1960–302.Einspruch, Norman G., Witterholt, E. J., Truell, Rohn, “Scattering of a Plane Transverse Wave by a Spherical Obstacle in an Elastic Medium,” J. Appl. Phys. 31, 806–818 (1960). A consideration of the scattering of a shear wave by a spherical discontinuity.Google Scholar
- 1965–303.Johnson, Gregert and Truell, Rohn, “Numerical Computations of Elastic Scattering Cross Sections,” J. Appl. Phys. 36, 3466–3475 (1965). A brief review of the calculation of cross section expressions for the scattering of an elastic wave in an elastic medium, with numerical calculations.Google Scholar
- 1975–304.Gubernatis, J. E., Domany, E., Huberman, M. and Krumhansl, J. A., “Theory of the Scattering of Ultrasound by Flaws,” Proc. 1975 IEEE Ultrason. Symp., 107–110. “An integral equation governing the scattering of ultrasound by an arbitrarily shaped flaw is presented, and features of the scattered displacement and stress fields are discussed for the case of a flaw embedded in an isotropic medium. Also discussed are differential cross sections for the scattered power. These cross sections for a spherical flaw (cavity and inclusion) are evaluated by an approximation analogous to the first Born approximation in quantum mechanical scattering. The results of the calculations are compared with exact results for scattering of ultrasound by spheres. The relevance of this comparison to NDE, i.e., flaw identification, is discussed.” (Author) 3 refs.Google Scholar
- 1958–305.White, R. W., “Elastic Wave Scattering at a Cylindrical Discontinuity in a Solid,” J. Acoust. Soc. Am. 30, 771–785 (1958). Deals with the scattering of plane compressional and shear waves at oblique incidence on an infinite elastic rod embedded in another isotropic elastic medium. It pays particular attention to mode conversion. It also reports some measurements.Google Scholar
- 1948–306.Fridman, M. M., “The Diffraction of a Plane Elastic Wave by a Semi-Infinite Rigid Plane,” Dokl. Akad. Nauk. USSR 60, 1145–1148 (1948), (in Russian). The first solution for scattering from a two-dimensional flaw.Google Scholar
- 1953–307.Maue, A.-W., “Die Bengung Elasticher Wellen an der Halbebene,” Z. F. Ang. Math. and Mech. 33, 1–10 (1953). An exact reduction to quadratures of the two-dimensional problem of elastic scattering of an infinite half-plane weak crack. The differential wave equations and boundary conditions are combined into integral equations for the potentials, which are represented as plane-wave superpositions. The integral equations are solved by the method of Clemmow. (In German.)Google Scholar
- 1964–308.Ang, D. D. and Knopoff, L., “Diffraction of Scalar Elastic Waves by a Clamped Finite Strip,” Proc. N.A.S. 51, 471–476 (1964). The long-wavelength limit to the solution of the far field for the title problem.Google Scholar
- 1964–309.Ang, D. D. and Knopoff, “Diffraction of Scalar Elastic Waves by a Finite Crack,” Proc. N.A.S. 51, 593–598 (1964). Similar to (308) except that the strip has weak boundary conditions (weak crack), which is a more important problem in applications.Google Scholar
- 1964–310.Ang, D. D. and Knopoff, L., “Diffraction of Vector Elastic Waves by a Clamped Finite Strip,” Proc. N. A. S. 52, 201–207 (1964). An extension of the calculation of (308).Google Scholar
- 1964–311.Ang, D. D. and Knopoff, L., “Diffraction of Vector Elastic Waves by a Finite Crack,” Proc. N.A.S. 52, 1075–1081 (1964). This paper considers the problem of the diffraction of an incident plane longitudinal wave by a finite crack, and evaluates the far fields by the method of steepest descents.Google Scholar
- 1976–312.Tan, T. H., “Theorem on the Scattering and the Absorption Cross Section for Scattering of Plane, Time-Harmonic, Elastic Waves,” J. Acoust. Soc. Am. 59, 1265–1267 (1976). A method, due to de Hoop, is extended to the scattering of elasto-dynamic waves to derive the “cross-section theorem” (the optical theorem).Google Scholar
- 1977–313.Varatharajulu, V.,* “Reciprocity Relations and Forward Amplitude Theorems for Elastic Waves,” J. Math. Phys. 18, 537–543 (1977). This paper derives the forward scattering (optical) theorem and receiprocity relations (including polarization change on scattering) for plane, monochromatic elastic waves scattered by obstacles of arbitrary shape. *Now Varadan.Google Scholar
- 1977–314.Gubernatis, J. E., Domany, E., and Krumhansl, J. A., “Formal Aspects of the Theory of the Scattering of Ultrasound by Flaws in Elastic Materials,” J. Appl. Phys. 48, 2804–2811 (1977). This paper considers the general theory of the scattering of ultrasound by flaws. It considers an incident plane wave scattering from a single homogeneous flaw in an isotropic elastic medium, and obtains an integral equation to describe the problem. The integration is over a volume, and this appears to be the first report to present the volume formulation for elasticity in a reasonably complete form. It derives expressions for scattered amplitudes and differential cross sections, and an optical theorem.Google Scholar
- 1977–315.Tan, T. H., “Reciprocity Relations for Scattering of Plane, Elastic Waves,” J. Acoust. Soc. Am. 61, 928–931 (1977). Reciprocity relations for scattering of plane, elastic waves incident upon a finite, linear, reciprocal obstacle in a homogeneous, isotropic, perfectly elastic medium are investigated.Google Scholar
- 1976–316.Pao, Yih-Hsing and Mow, C. C, “Theory of Normal Modes and Ultrasonic Spectral Analysis of the Scattering of Waves in Solids,” J. Acoust. Soc. Am. 59, 1046–1056 (1976). A theory of the spectral analysis of the scattering of elastic waves is presented and illustrated with numerical results for the scattering by a circular cylindrical fluid inclusion in a solid. From overtone frequencies the ratio of the wave speed to the radius of the inclusion can be determined. The application of this technique to nondestructive testing is discussed.Google Scholar
- 1976–317.Pao, Yih-Hsing and Varatharajulu,* Vasundara, “Huygens’ Principle, Radiation Conditions, and Integral Formulas for the Scattering of Elastic Waves,” J. Acoust. Soc. Am. 59, 1361–1371 (1976). By using the divergence theorem this paper shows how Helmholtz- and Kirchhoff-type integral formulas can be derived. Both “interior” and “exterior” formulas are obtained; these formulas are necessary for investigating the scattering of elastic waves by bounded objects. The results illustrate Huygens’ principle for the two wave fronts of the elastic wave field. *Now Varadan.Google Scholar
- 1977–318.Gubernatis, J. E., Domany, E., Krumhansl, J. A., and Huberman, M., “The Born Approximation in the Theory of Scattering of Elastic Waves by Flaws,” J. Appl. Phys. 48, 2812–2819 (1977). The integral equation formulation obtained in 77–1 is used to derive an approximation scheme, which may be applied relatively easily to scatterers of complicated shapes. The approximation works best for backscattered long waves, but in certain cases is surprisingly good even for short wavelengths and all angles.Google Scholar
- 1959–319.Karal, Frank C., Jr., and Keller, Joseph B., “Elastic Wave Propagation in Homogeneous and Inhomogeneous Media,” J. Acoust. Soc. Am. 31, 694–705 (1959). This is the extension of Keller’s geometrical theory of diffraction to elastic waves. It gives a general method for solving linearized elastic-wave problems which does not depend on the possibility of separation of variables. The method should work well for short wavelengths, but experience had shown that it was still useful for wavelengths of the same order of magnitude as other dimensions in the problem.Google Scholar
- 1978–320.Weight, J. P. and Hayman, A. J., “Observations of the Propagation of Very Short Ultrasonic Pulses and Their Reflection by Small Targets,” J. Acoust. Soc. Am. 63 (2), 396–404. “The field of a circular ultrasonic transducer emitting a single-cycle pulse into water has been observed using a specially constructed small (150 ym) wide-band receiving probe and a compact stroboscopic schlieren system. The theoretically predicted plane-wave and diffracted edge-wave components of the field have been resolved. Good agreement with the theory for a pistonlike source is obtained, except in a region less than 1.5 transducer radii from the transducer. The output of the transducer used in the transmit-receive mode to detect small targets has been measured and the results are in accord with a time-domain principle of reciprocity between transmission and reception. Implications of the results for field plotting and for the location and characterization of small targets are considered.” (Author) 27 refs.Google Scholar
- 1975–321.Richardson, J. M. and Tittmann, B. R., “Deducing Subsurface Property Gradients from Surface Wave Dispersion Data,” Proc. 1975 IEEE Ultrason. Symp., 488–491. “Because of the ill-posed nature of the problem, special mathematical techniques must be used to convert surface wave dispersion data into subsurface property measurement. The solution is approached here within the framework of estimation theory. This approach starts with a mathematical model giving a probabilistic description of the possible results of measurement and then the optimal estimate is obtained as the most probable value within the constraints imposed by the actual measurements. Estimation theory also yields auxiliary measures pertaining to bias, data vs. model dominance, resolution and a posteriori variance. The theory is applied to actual experimental data consisting of the phase velocities of Rayleigh surface waves in surface-hardened steel at a set of four wavelengths. The estimated profile of hardening is compared with independent destructive measurements. As a test, the theory is also applied at the same set of wavelengths to a set of synthetic data calculated from an assumed profile. The above auxiliary measures giving properties of the estimator are also discussed.” (Authors) 5 refs.Google Scholar
- 1978–322.Lewis, D. K., Szilas, P., Fitting, D. W., and Adler, L., “Spectrum Analysis of Elastic Wave Scattering from Cracks in Metals,” J. Acoust. Soc. Am. 63, Suppl. No. 1, 974. Here experiments are compared to Keller’s theory for elastic wave diffraction, with Maue’s solution serving as the canonical problem.Google Scholar
- 1977–323.Achenbach, J. D. and Gautesen, A. K., “Geometrical Theory of Diffraction for Three-D Elastodynamics,” J. Acoust. Soc. Am. 61, 413–421. Here Keller’s geometrical diffraction theory is applied to three-dimensional elastodynamics, particularly to the diffraction of longitudinal waves by a crack. This yields approximations useful for large frequencies and/or large distances from the crack edge. As an example the diffraction of a point-source field by a semi-infinite crack is worked out in detail.Google Scholar
- 1978–324.Gautesen, A. K., Achenbach, J. D., and McMaken, H., “Surface-Wave Rays in Elastodynamic Diffraction by Cracks,” J. Acoust. Soc. Am. 63, 1824–1831. This is the first study of the contributions to the diffracted fields which come, not from diffracted rays of longitudinal and transverse motion, but from rays of surface waves. These provide the main contributions on the faces of the crack. As an example the problem of a plane longitudinal wave normally incident on a penny-shaped crack is worked out in some detail.Google Scholar
- 1977–325.Datta, S. K., “Diffraction of Plane Elastic Waves by Ellipsoidal Inclusions,” J. Acoust. Soc. Am. 61, 1432–1437. The method of matched asymptotic expansions is used to get a low-frequency solution for the diffraction of a plane wave by an elastic ellipsoidal inclusion. Numerical results are given, and applicability to NDE is discussed.Google Scholar
- 1976–326.Waterman, P. C., “Matrix Theory of Elastic Wave Scattering,” J. Acoust. Soc. Am. 60, 567–580.Google Scholar
- Earlier developm.ents of a matrix theory for acoustic and EM scattering are here extended by their developer to elastic waves. If certain matrix elements which express mode conversion are set to zero, the elastic matrix equations reduce to a superposition of acoustic and EM equations, providing a unified theory of scattering of acoustic, EM and elastic waves by an obstacle of arbitrary geometry and making available the entire body of acoustic and EM results to compare the elastic theory with. The matrices are symmetric and unitary.Google Scholar
- 1976–327.Varatharajulu, V.,* and Pao, Y.-H., “Scattering Matrix for Elastic Waves. 1. Theory,” J. Acoust. Soc. Am. 60, 556–566. This paper extends the already existing scattering matrix approach of Waterman to the scattering of elastic waves. The method is applicable to obstacles of arbitrary shape so one does not have to calculate a special set of wave functions for each geometry. The matrices are symmetric and unitary, which is very nice because these properties are essential for checking the numerical accuracy. *Now Varadan.Google Scholar
- 1978–328.Waterman, P. C, “Matrix Theory of Elastic Wave Scattering. II. A New Conservation Law,” J. Acoust. Soc. Am. 63, 1320–1325. A new conserved elastodynamic field quantity is found; this new conservation requirement may lead to deeper physical understanding and to simpler computational methods using the scattering-matrix theory.Google Scholar
- 1978–329.Varadan, Vasundara V., “Scattering Matrix for Elastic Waves. II. Application to Elliptic Cylinders,” J. Acoust. Soc. Am. 63, 1014–1024. The scattering-matrix approach to elastic wave scattering is here employed to give numerical results for scattering of obliquely-incident plane waves from a cylinder of elliptic cross section. It is much more useful for short wavelengths than for long.Google Scholar
- 1978–330.Varadan, Vijay K., Varadan, Vasundara V., and Pao, Yih-Hsing, “Multiple Scattering of Elastic Waves by Cylinders of Arbitrary Cross Section. I. SH Waves., J. Acoust. Soc. Am. 63, 1310–1319. The problem here is many identical, long, parallel randomly distributed cylinders of arbitrary cross section, scattering time-harmonic polarized plane shear waves. The method combines the scattering-matrix approach and a statistical averaging technique. Numerical results are presented.Google Scholar
- 1972–331.Boore, David M., “Finite Difference Methods for Seismic Wave Propagation in Heterogeneous Materials,” Methods in Computational Physics 11, 1–37. A review article on the computation of elastic wave propagation in media whose properties change with position, by finite difference methods.Google Scholar
- 1972–332.Lysmer, John and Drake, Lawrence A., “A Finite Element Method for Seismology,” Methods in Computational Physics 11, 181–216. A presentation of a finite element method for surface waves which pays attention to computational feasibility.Google Scholar
- 1976–333.Datta, S. K., “Scattering of Elastic Waves by a Distribution of Inclusions,” Arch. Mech. Stos. 28, 317–324. The problem of scattering of plane P-waves off a uniform distribution of rigid spheroids is treated by combining the method of matched asymptotic expansions and a suitable configurational averaging method.Google Scholar
- 1975–334.Vary, A., “Feasibility of Ranking Fracture Toughness by Ultrasonic Measurements,” Proc. 1975 IEEE Ultrason. Symp., 588–590. “Preliminary experimental verification was made of the expected correlation between ultrasonic attenuation parameters and fracture toughness measurements on a set of maraging steel specimens. An empirical equation is proposed for relating the fracture toughness property K
_{c}to the ultrasonic properties of a polycrystalline solid. The pertinent ultrasonic factors in this case involve the attenuation coefficient a, frequency f, and 3, the slope of the a vs. f curve. The proposed relation has the form K_{c}= ∅β_{f}. It predicts that the fracture toughness property K_{c}will be proportional to the attenuation slope 3 evaluated over an appropriate frequency range. The results of this feasibility study with maraging steel specimens indicate that if various specimens of a given metal possess different fracture toughness, it is possible to rank them in order of toughness by ultrasonic testing.” (Author) 9 refs.Google Scholar - 1976–335.Sobczyk, K., “Elastic Wave Propagation in a Discrete Random Medium,” Acta Mechanica 25, 13–28. This paper considers propagation of elastic waves in an infinite solid containing a random configuration of identical finite scatterers. The work was stimulated by practical questions in geophysics and ultrasonic spectroscopy. It gives a general formulation for scatterers of arbitrary shape, and solutions for specific cases of spherical scatterers. The English has a Polish flavor.Google Scholar
- 1974–336.Keer, L. M. and Luong, W. C., “Diffraction of Waves and Stress Intensity Factors in a Cracked Layered Composite,” J. Acoust. Soc. Am. 56, 1681–1686. Layers in composite materials act somewhat as waveguides; this study considers the effect of a crack perpendicular to the layer, and shows that it gives rise to scattered waves in the layer which could be detected at a large distance from the flaw.Google Scholar
- 1975–337.Keer, L. M., Luong, W. C. and Achenbach, J. D., “Elastodynamic Stress Intensity Factors for a Crack in a Layered Composite,” J. Acoust. Soc. Am. 58, 1204–1210. This studies the effect of a. crack parallel to the layer (cf. 74–2); the ease of detection of the flaw depends on the stiffness of the layer, with flaws in relatively stiff layers being harder to detect.Google Scholar
- 1974–338.Christensen, R. M., “Wave Propagation in Elastic Media with a Periodic Array of Discrete Inclusions,” J. Acoust. Soc. Am. 55, 700–707. This studies the propagation of waves in a homogeneous, isotropic medium containing an array of discrete inclusions of another material. Full account is taken of multiple scatterings. The direction of propagation is restricted to be one of the symmetry directions of the material (which has cubic symmetry). A perturbation method is used.Google Scholar
- 1978–339.Simons, Donald A., “Reflection of Rayleigh Waves by Strips, Grooves and Periodic Arrays of Strips or Grooves,” J. Acoust. Soc. 63, 1292–1301. Devices incorporating grooves and strips are used to perform certain microwave signal-processing applications, and this is the most recent paper on the title problem, with references to earlier work. Integral equations are solved by perturbation techniques.Google Scholar
- 1978–340.Gaunard, G. C. and H. Uberall, “Theory of Resonant Scattering from Spherical Cavities in Elastic and Viscoelastic Media,” J. Acoust. Soc. Am. 63, 1699–1712. This paper studies theoretically the scattering of a plane p-wave by a fluids-filled spherical cavity in elastic and viscoelastic (hence absorbing) media. The approach, new to elastodynamics and acoustics, is familiar in nuclear scattering theory. Numerical computations are presented.Google Scholar
- 1977–341.Tan, T. H., “Scattering of Plane, Elastic Waves by a Plane Crack of Finite Width,” Appl. Sci. Res. 33, 75–100. This paper considers the diffraction of time-harmonic, vertically polarized (the problem involving horizontally polarized waves has already been dealt with extensively in the literature), plane elastic waves by a crack of finite width using the integral-equation method. Numerical solutions are presented.Google Scholar
- 1976–342.Tan, T. H., “Diffraction of Time-Harmonic Elastic Waves by a Cylindrical Obstacle,” Appl. Sci. Res. 32, 97–144. An integral equation formulation of the diffraction of two-dimensional elastic waves by a cylindrical obstacle is presented. For a number of configurations the integral equations are solved numerically. Also numerical results on power scattering and extinction cross sections are given.Google Scholar
- 1975–343.Rose, Joseph L. and Paul A. Meyer, “Model for Ultrasonic Field Analysis in Solids,” J. Acoust. Soc. Am. 57, 598–605. “This paper concentrates on one of the most basic ultrasonic problems in NDT: that of evaluating the ultrasonic field characteristics in a solid material resulting from a pulsed piezoelectric crystal” (authors). It presents a theoretical model that can be used to evaluate analytically ultrasonic transducer longitudinal wave-generation characteristics in homogeneous isotropic solids. Results depend on the spectrum of the input pulse.Google Scholar
- 1974–344.Chow, T. S., “Scattering of Elastic Waves in an Inhomogeneous Solid,” J. Acoust. Soc. Am. 56, 1049–1051. Plane harmonic elastic waves are propagating in an isotropic material containing randomly distributed inhomogeneities; results are expressed in terms of correlation functions.Google Scholar
- 1976–345.Israilov, M. Sh., “Certain Exact Solutions to Problems of Diffraction of Elastic Waves at a Segment,” Sov. Phys. Dokl. 21, 756–757 (from DAN SSSR 231, 1074–1076). Exact solutions for particular cases of diffraction of longitudinal and transverse waves in elastic media are given; one problem corresponds to diffraction at a rigid plate, another to diffraction at a slit. These are for transient plane waves.Google Scholar
- 1971–346.Kraft, David W., and Michael C. Franzblau, “Scattering of Elastic Waves from a Spherical Cavity in a Solid Medium,” J. Appl. Phys. 42, 3019–3024. This is extending the work of Truell and his collaborators; it gives the first numerical computations of the scattering cross section for an incident transverse wave.Google Scholar
- 1963–347+.Bogert, B. P., Healy, M. J. R., and Tukey, J. W., “The Frequency Analysis of Time Series for Echoes: Cepstrum, Pseudo-Autocovariance, Cross-Cepstrum and Saphe Cracking,” Chapter 15 in Time Series Analysis, Rosenblatt (editor), Wiley (1963). The authors introduce the technique of cepstral processing. The use of this method for detecting time separation of “echoes” in the presence of various sources of noise is explored.Google Scholar
- 1969–348+.Cooley, J. W., Lewis, P. A. W., and Welch, P. D., “The Fast Fourier Transform and its Applications,” IEEE Trans. Educ. E-12 (1), 27. “The advent of the fast Fourier transform method has greatly extended our ability to implement Fourier methods on digital computers. A description of the algorothm and its programming is given here and followed by a theorem relating its operands, the finite sample sequences, to the continuous functions they often are intended to approximate. An analysis of the error due to discrete sampling over finite ranges is given in terms of aliasing. Procedures for computing Fourier integrals, convolutions and lagged products are outlined” (author). A FORTRAN subroutine is given for computing the discrete Fourier transform by the FFT method.Google Scholar
- 1967–349+.Singleton, R. C, “A Method for Computing the Fast Fourier Transform with Auxiliary Memory and Limited High-Speed Storage,” IEEE Trans. Audio Electroacoust. AU-15, 91–97. “A method is given for computing the fast Fourier transform of arbitrarily large size using auxiliary memory files, such as magnetic tape or disk, for data storage. Four data files are used, two in and two out. A multivariate complex Fourier transform of n = 2m data points is computed in m passes of the data, and the transformed result is permuted to normal order by m-1 additional passes. With buffered input-output, computing can be overlapped with reading and writing of data. Computing time is proportional to n log2 n. The method can be used with as few as three files, but file passing for permutation is reduced by using six or eight files. With eight files, the optimum number for a radix 2 transform, the transform is computed in m passes without need for additional permutation passes. An ALGOL procedure for computing the complex Fourier transform with four, six, or eight files is listed, and timing and accuracy test results are given. This procedure allows an arbitrary number of variables, each dimension a power of 2” (author).Google Scholar
- 1969–350+.Singleton, R. C, “An Algorithm for Computing the Mixed Radix Fast Fourier Transform,” IEEE Trans. Audio Electroacoust. AU-17, 93–103. “This paper presents an algorithm for computing the fast Fourier transform, based on a method proposed by Cooley and Tukey. As in their algorithm, the dimension n of the transform is factored (if possible), and n/p elementary transforms of dimension p are computed for each factor p of n. An improved method of computing a transform step corresponding to an odd factor of n is given; with this method, the number of complex multiplications for an elementary transform of dimension p is reduced from (p-1)2 to (p-l)2/4 for odd p. The fast Fourier transform, when computed in place, requires a final permutation step to arrange the results in normal order. This algorithm includes an efficient method for permuting the results in place. The algorithm is described mathematically and illustrated by a FORTRAN subroutine” (Author).Google Scholar
- 1975–351.Burgess, J. C., “On Digital Spectrum Analysis of Periodic Signals,” J. Acoust. Soc. Am. 58 (3), 556–567. “Digital spectrum analysis of harmonic signals can result in amplitude estimates in error as much as 3.92 dB. The corresponding frequency estimates are not exact. The paper presents a general method for obtaining significantly improved estimates of amplitude and frequency. Criteria are given which allow specification of an error limit. Specific equations are given for sample signals that are unmodified (open window) and for signals modified by a Hamming data window. The phenomenon called “leakage” is shown to result from discontinuities imposed by the computation process at the periodically extended “ends” of a sample signal and not, as is often supposed, by discontinuities presumed to exist (but do not) at the “ends” of the open window. Criteria for window selection to reduce leakage are discussed. Calibration is specifically treated. When any data window other than the open window is used, a different calibration must be applied to periodic and random components in a signal. Although discussion is limited to a single harmonic signal, the method can be applied in a straightforward way to signals with multiple harmonics” (Author) 32 refs.Google Scholar
- 1966–352+.Gauster, W. B. and Breazeale, M. A., “Detector for Measurement of Ultrasonic Strain Amplitudes in Solids,” Rev. Sci. Instrum. 37 (11), 1544–1548. “A capacitive detector has been developed for strain amplitude measurements of longitudinal ultrasonic waves in the frequency range from 5 to 100 MHz. The sensitivity of the device is such that displacement amplitudes of the order of 10–10 cm can be detected. As a check of the technique, quantitative measurements of the harmonic distortion of ultrasonic waves in a single crystal of germanium were made. From the results, some combinations of third-order elastic constants are calculated and are compared with values obtained with the same sample by another method” (authors) 11 refs.Google Scholar
- 1977–353+.Cantrell, J. H., Jr. and Breazeale, M. A., “Elimination of Transducer Bond Corrections in Accurate Ultrasonic Wave Velocity Measurements by Use of Capacitive Transducers,” J. Acoust. Soc. Am. 61 (2), 403–406 “A capacitive-driver-capacitive detector system for generation and detection of ultrasonic waves has been developed. This eliminates the necessity of bonding piezoelectric transducers to solid samples. With the capacitive-driver-capacitive-detector system, free-free boundary conditions exist at the sample surfaces and longitudinal ultrasonic-wave velocities in solids can be measured accurately without correcting for ultrasonic-wave phase shifts due to sample-bonded transducer interfaces. The capacitive driver has a mica dielectric which increases the breakdown potential, but maintains the free-free boundary conditions at the solid specimen surfaces. This allows for a larger-amplitude ultrasonic signal to be generated in the sample than is possible with an air-gap capacitive driver. This improves the precision of the measurement. The accuracy of the method is comparable with that of bonded-transducer methods, after bond corrections are made” (author) 14 refs.Google Scholar
- 1971–354.Kazys, R. J. and Domarkas, V., “The Frequency and Transient Response of Piezotransducers with Intermediate Layers and Electrical Matching Circuits,” Proc. 7th Int. Congress on Acoustics, Session 25U3 (Budapest, 1971). “This investigation includes the action of intermediate layers, backing and electrical matching circuits on frequency and transient responses of thickness vibrating piezotransducers operating in liquids . . . Consideration is given to frequency and phase response of the system piezotransmitter-piezoreceiver ...” (author) 5 refs.Google Scholar
- 1977–355.Kazys, R. and Lukosevicius, A., “Optimization of the Piezoelectric Transducer Response by Means of Electrical Correcting Circuits,” Ultrasonics, 111–116 (May 1977). “A method of shortening the transient response of a piezoelectric transducer is described. It can be applied to thickness mode piezoelectric transducers of arbitrary electromechanical coupling. The system incorporates electrical correcting circuits and can produce a transient response with a duration much shorter than the transit time of an ultrasonic wave traveling through the piezoelectric plate” (authors) 6 refs.Google Scholar
- 1976–356.Lizzi, F., Katz, L., St. Louis, L. and Coleman, D. J., “Applications of Spectral Analysis in Medical Ultrasonography,” Ultrasonics, 77–80 (March 1976). “Spectral analysis of ultrasonic reflections from biological tissues can be used to determine basic tissue parameters for use in differential diagnosis. This paper describes the use of the technique under circumstances encountered in several types of clinical examinations. The applications are illustrated with results obtained from laboratory measurements with a system now being employed in a clinical evaluation programme. The test objects studied simulate tissues with planar boundaries, tissues with heterogeneous interior structure, and tissues causing acoustic ‘shadowing’ of posterior regions” (authors) 6 refs.Google Scholar
- 1975–357.Lele, P. P., Mansfield, A. B., Murphy, A. I., Namery, J., and Senapati, N., “Tissue Characterization by Ultrasonic Frequency-Dependent Attenuation and Scattering,” Proc. Sem. Ultrason. Tissue Charac., NBS Special Pub. 453. “Studies conducted in this laboratory to explore the feasibility of utilizing acoustic impedance, attenuation, and scattering characteristics of tissues for enhancing the diagnostic capabilities of ultrasound are described. Frequency-dependent ultrasonic attenuation is found to be sufficiently greater in infarcted or otherwise necrotized tissues than in normal controls to permit their positive identification. Superficial and internal scattering properties of tissues hold the promise of being significant for diagnostic applications. The difficulties that will have to be overcome to successfully utilize these properties are discussed” (authors) 24 refs.Google Scholar
- 1978–358.Serabian, S. and Williams, R. S., “Experimental Determination of Ultrasonic Attenuating Characteristics Using the Roney Generalized Theory,” Mat. Eval. 55–62 (July 1978). “To date, little use has been made of the generalized theory of ultrasonic attenuation in polycrystalline materials proposed by Roney. It is the only generalized theory which appears to run the gamut of grain size and frequency dependency of attenuation from the hysteresis loss mechanism through the complete scattering losses, i.e., Rayleigh, phase and diffusion. The theory requires only two constants—a hysteresis constant for the hysteresis losses and a scattering coefficient to describe those losses due to scattering. In the frequency range normally associated with the ultrasonic interrogation method the hysteresis losses are essentially negligible, thus, the scattering coefficient can fully describe the ability of a given material to propagate ultrasound. Moreover, this assessment of the material can be made without necessitating direct inferences to the grain size or frequency involved” (authors) 30 refs.Google Scholar
- 1973–359.Kesler, N. A., Merkulov, L. G., Shmurun, Y. A., and Tokarev, V. A., “Ultrasonic Spectral Method for Attenuation Measurement and Device for Automatic Testing of Microstructure of Materials,” Proc. 7th Int. Conf. on NDT, Session J-34 (Warszawa, 1973). This paper presents the mathematics and an experimental technique for determining the attenuation in a plane parallel plate, over a band of ultrasonic frequencies. 3 refs.Google Scholar
- 1974–360.Heyser, R. C. and Le Croissette, D. H., “A New Ultrasonic Imaging System Using Time Delay Spectrometry,” Ultrasound in Med. and Biol. 1, 119–131. “A new method of forming a visual image by ultrasound is described. A shadowgraphic transmission image similar to an x-ray radiograph is produced by the application of a technique known as Time Delay Spectrometry. The system uses a repetitive frequency sweep with a linear relationship between frequency and time and the transmitting and receiving crystal are scanned in raster fashion about the subject. By electronic processing, an image may be built up which represents the energy transmitted through the specimen with a given time delay. An intensity modulated picture encompassing the full shades-of-gray capability of the recording system can be produced. A second type of image showing transmission time through the specimen may also be formed. Brightness changes in the displayed image in this case correspond to changes in the ultrasonic transmission time through the specimen. There is no analog for this type of image in current x-ray or ultrasonic practice. Examples of both types of images of specimens both in vitro and in vivo are shown. The advantages and potentials of this method for biomedical ultrasonic imaging and analysis are discussed” (author) 6 refs.Google Scholar
- 1975–361.Alers, G. and Graham, L. J., “Reflection of Ultrasonic Waves by Thin Interfaces,” Proc. 1975 IEEE Ultrason. Symp., 579–582. “In order to measure the quality of an adhesive bond using ultrasonic waves, it is important to recognize those features in a reflected echo that carry information about the structure of the thin, chemically different interface between the adhesive and the adherend. We have studied the frequency dependence of the phase and amplitude of ultrasonic pulses reflected from very thin bonds formed between identical blocks of Lucite so that the reflection process is dominated by the nature of the interface and not by the impedance mismatch that occurs in practical adhesive to metal joints. The results show a frequency independent reflection coefficient over the range of 2.5 to 10 MHz which is very difficult to fit with currently available models of reflection from thin layers” (authors) 5 refs.Google Scholar
- 1971–362.Lees, S., “Ultrasonic Measurement of Thin Layers,” IEEE Trans. Son. Ultrason., SU-18 (2), 81–86. “The shape of a pulse echo from a thin layer embedded between two thicker media is changed because the successive echoes from the two close interfaces overlap. A simple computer algorithm is developed for real time computation of the change in shape as a function of the film thickness. It is only necessary to know the specific acoustic impedances of the three media. In one experiment castor oil was embedded between glass and steel. The calculated echoes closely resembled the experimental results for films between 1- and 38-μ thick. A curve was devised for estimating the film thickness from peak ratios in the echo. A second experimental situation appeared in testing acoustical transmission across an amalgam-tooth dentin boundary with water as the film medium. Numerical calculations produced the same echo patterns as were observed indicating that there is a gap in the interface between 1 and 10 μ in the samples” (author).Google Scholar
- 1978–363.Heyman, J. S., “Phase Insensitive Acoustoelectric Transducer,” J. Acoust. Soc. Am. 64 (1), 243. “Conventional ultrasonic transducers transform acoustic waves into electrical signals preserving phase and amplitude information. When the acoustic wavelength is significantly smaller than the transducer diameter, severe phase modulation of the electrical signal can occur. This results in anomalous attenuation measurements, background noise in Non-Destructive Evaluation (NDE), and in general complicates data interpretation. In this article, we describe and evaluate a phase insensitive transducer based on the acoustoelectric effect. Theory of operation of the Acousto-Electric Transducer (AET) is discussed and some optimization procedures outlined for its use. Directivity data for the AET is contrasted with a conventional piezoelectric transducer. In addition, transmission scanning data of phantom flaws in metal plates is presented for both transducers and demonstrates a significant improvement in resolution with the AET” (author).Google Scholar
- 1966–364.Carome, E. F., Moeller, C. E. and Clark, N. A., “Intense Ruby-Laser-Induced Acoustic Impulses in Liquids,” J. Acoust. Soc. Am. 40 (6), 1462. “An experimental study has been made of the acoustic signals induced in liquids by the focused beam from a Q-spoiled ruby laser. Very intense acoustic impulses have been produced with laser pulses of less than 0.05 J total energy. These appear to be generated by dielectric breakdown and not associated with the hypersonic waves that may be produced simultaneously by stimulated Brillouin scattering. The observed impulses have peak pressures of approximately 500 atm and frequency components in excess of 2400 Mc/sec.” (Authors), 8 refs.Google Scholar
- 1977–365.von Gutfield, R. J. and Melcher, R. L., “20 MHz Acoustic Waves from Pulsed Thermoelastic Expansions of Constrained Surfaces,” J. Acoust. Soc. Am. 30 (6), 257–259. “Repetitive pulses from lasers with pulse widths 5–10 nsec or a current generator with 10–25-nsec widths have been used to launch acoustic waves by thermoelastic expansions. For the laser case, when transparent media such as quartz plates are used to acoustically constrain the energy absorbing surface, an increase of up to 46 dB at 20 MHz was observed over that generated from a free surface. An experiment using a scannable laser to generate elastic waves for flaw detection in a metallic sample is described.” (Author), 5 refs.Google Scholar
- 1973–366.Thompson, D. O., editor of Proceedings of the Interdisciplinary Workshop on Nondestructive Testing — Materials Characterization, AFML-TR-73–69, April 1973. “The field of nondestructive testing and materials characterization is examined with emphasis on new approaches that may lead to significantly improved future capabilities. The presentations range from examples of present capabilities and limitations to field of basic research. The recommendations of four panels are presented for future research and development to advance the present state-of-the-art.” (Editor)Google Scholar
- 1975–367.Thompson, D. O., “Interdisciplinary Program for Quantitative Flaw Definition — Special Report First Year Effort,” ARPA/AFML Contract F33615–74-C-5180 This report contains summaries of work performed in: (1) Quantitative Flaw Definition - piezoelectric and electromagnetic transducers - data processing - theoretical and experimental work on scattering of ultrasound from defects - system integration - sample preparation (2) Bond Strength - acoustical interactions at thin interfaces - nature of bonded interface degradation in composites (3) Failure Prediction - determination of residual stresses in structural material - acoustic emission 1975–368 Lakin, K. M., “Piezoelectric Transducers,” Project I, Unit I, Task 1, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 8–16. Work is presented on transducer construction, transducer circuit modeling and the construction of a data acquisition system for use in radiation field pattern analysis. 2 refs.Google Scholar
- 1975–369.Maxfield, B. W., “Optimization and Application of Electrodynamic Acoustic Wave Transducers,” Project I, Unit I, Task 2, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 17–32. Electromagnetic acoustic wave transducers (EMATS) are analyzed theoretically. The acoustic field predicted is compared to that produced in an experimental system. 1 ref.Google Scholar
- 1975–370.White, R. M, and Kerber, G. L., “Analog Data Processing,” Project I, Unit II, Task 2, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 51–56. The rationale for deconvolution filtering is discussed. A system, utilizing a surface acoustic wave (SAW) filter, is presented. 1 ref.Google Scholar
- 1975–371.Yee, B. G. W., Couchman, J. C. and Bell, Jr., “Digital Techniques for Ultrasonic Flaw Characterization,” Project I, Unit II, Task 3, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 57–85. The hardware and software for these investigator’s data collection and signal processing system are described. Numerous timed and frequency domain signatures for spheroids and flat-bottomed holes were acquired— many are presented. Preliminary comparisons with theory are discussed.Google Scholar
- 1975–372.Adler, L., “Models for the Frequency Dependence of Ultrasonic Scattering from Real Flaws,” Project I, Unit III, Task 1, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 86–111. The author discusses a geometrical theory of diffraction for acoustic waves (based on the electromagnetic theory of Keller). The author’s experimental system for studying the angular and frequency dependence of acoustic wave scattering from defects is presented. Theory and experiment agree reasonably well, with excellent agreement as to the spacing of nulls in the spectra. 4 refs.Google Scholar
- 1975–373.Packman, P. F. and Coyne, E. J., “Defect Characterization by Spatial Distribution of Ultrasonic Scattered Energy,” Project I, Unit III, Task 2, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 112–127. “The ability of the ultrasonic indicia to characterize the shape and size of imbedded defects has been developed and examined.” (Author), 23 refs.Google Scholar
- 1975–374.Tittmann, B. R., “Comparison of Theory and Experiment for Ultrasonic Scattering from Spherical and Flat-Bottom Cavities,” Project I, Unit III, Task 3, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 128–139. The author compares his experimental measurements to the theory of Ermolov (solution of a scalar potential equation for normal incidence of longitudinal waves on a rigid, motionless disk in a fluid). Agreement is good considering the simplicity of Ermolov’s solution. 5 refs.Google Scholar
- 1975–375.Krumhansl, J. A., Gubernatis, J. E., Huberman, M., and Domany, E., “Theoretical Studies of Flaws and NDE,” Project I, Unit III, Task 4, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 140–144. “1. The general information of integral equation scattering theory for vector elastic waves has been reviewed and summarized in a report just being completed. While there is much literature (acoustic) for scalar wave problems, we believe this to be the first time that the details for elastic wave systems have been documented. Our writeup can serve as a source for this theory. 2. The first Born approximation to the general integral equation has been obtained both in analytic form, and programmed for computations. 3. For spherical flaws, the exact partial wave solutions in the literature (Truell et al.) have been checked [some algebraic corrections], programmed, and evaluated. 4. Thus, we have computed Born approximation and exact scattering, of incident longitudinal or transverse waves by spherical scatterers — as a function of scattering angle (0 – 180°) and for kr
_{s}from 0 to about 6. The cases considered are (a) spherical holes in Al, Ti, and stainless steel, and (b) Al and stainless steel spheres in aluminum. 5. The practically useful conclusion is that there are many useful regimes of the first Born approximation — which because of its relative simplicity does not require extensive computing effort for use. This shows promise as a first approximation to explore scattering pattern features (signatures).” (Authors)Google Scholar - 1975–376.Kraut, E. A., “Review of Theories of Scattering of Elastic Waves by Cracks,” Project I, Unit IV, Task 1, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 145–162. Scattering of elastic waves by a 2-dimensional crack of arbitrary shape in an unbounded elastic medium is considered. The Kirchhoff approximation is discussed, and the scattering from a penny-shaped crack is investigated. 44 refs.Google Scholar
- 1975–377.Alers, G. A. and Graham, L. J., “Ultrasonic Wave Interaction with Interfaces,” Project II, Unit I, Task 1, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 183–196. “Adhesive bonds of different mechanical strength, between identical materials, were fabricated by both chemical and thermal means.” (Author) The frequency dependence of the amplitude of ultrasonic signals from the bonds is experimentally determined and compared to theoretical models and to the bond strength. 5 refs.Google Scholar
- 1975–378.Rose, J. L. and Meyer, P. A., “Ultrasonic Signal Processing Methods for Adhesive Bond Strength Measurements,” Project II, Unit I, Task 2, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 197–231. “The purpose of this work is to examine the effects of selected attenuation functions in adhesive bond modeling problems so that the attenuation in signal processing and interpretation can be treated adequately. Bond models are presently being used to study such problems as improper substrate surface preparation, improper adhesive cure, or chemical segregation of the adhesive. .,. . Results indicate that attenuation effects can substantially alter the ultrasonic reflection even though the bondline is relatively thin. ...” (Authors)Google Scholar
- 1974–379.Tittmann, B. R. and Cohen, E. R., “Acoustic Wave Scattering from a Sphere,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238, 173–186. “The objective of this program is to calculate the frequency and angular dependence of the ultrasonic energy scattered from a solid ellipsoid of revolution embedded in another solid. This calculation must take into account the mode conversion that takes place at the boundaries of the ellipsoid. The first phase will concentrate on the spherical case so that a simple ellipsoid can then be treated by perturbation methods. The vector and scalar potential problem for the sphere has been solved and is programmed onto the computer at the Science Center. In order to check this program, the case of a rigid, motionless sphere is being calculated because it can be compared to the results of a published calculation by Morse. An integral part of this program is an experimental check on the calculations performed by making accurate measurements of the angle and frequency dependence of the scattering of ultrasonic waves in the 1 to 15 MHz range. A 2–1/2 inch diameter by 2–1/2 inch thick sample containing a single spherical void 400 microns in diameter is being prepared by diffusion bonding techniques. Pure titanium has been chosen for the host material because it showed a minimum amount of attenuation and background scattering. Spheres of tungsten carbide and magnesium will also be embedded in other titanium samples so that a detailed study of mode conversion effects can be made.” (Author) 3 refs.Google Scholar
- 1974–380.Mucciardi, A. N., “Adaptive Nonlinear Modeling for Ultrasonic Signal Processing,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238, 194–212. “... The main objectives of this project are to evaluate the efficacy of adaptive nonlinear signal processing techniques to model material flaw descriptors with high accuracy. This modeling synthesis procedure has its expression in a nonlinear adaptive trainable network. The procedure is unique because a detailed knowledge of the underlying physical phenomena is not required. Indeed, it is believed that such information is contained implicitly in the experimental data, and it is the purpose of the methodology to extract this information and to generate models accordingly. ... In this current project, the feasibility of adaptive nonlinear signal processing techniques for UNDT will be demonstrated. In particular, adaptive trainable networks will be synthesized for characterization of UNDT waveforms for accurate inferences of: (1) flat-bottom-hole sizes, and (2) the length of fatigue cracks. . . . These results will provide important information to metallurgical investigators regarding the relationships between the best-found UNDT waveform parameter subsets and the underlying physical phenomena.” (Author)Google Scholar
- 1974–381.Moran, T. J., “Studies of Electromagnetic Sound Generation for NDE,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238, 213–223. “The technique of electromagnetic sound generation has been known since 1967. Since it provides a contactless means of generating ultrasonic waves in metals, application of the technique to NDE would eliminate the problem of coupling the transducer to the sample under evaluation. It is also an extremely flexible technique since it can be used to generate bulk and surface waves of all polarizations. At its present state of development, the technique is relatively inefficient in converting RF energy to sound energy in comparison to standard transducer techniques and it is also material dependent since the generation of the sound occurs inside the material near the surface. The goal of the present work is to first optimize the efficiency of the generation process and secondly, to perform a systematic study of the generation efficiency in many materials of present interest in manufacturing. We will use both unflawed samples and those with well-characterized flaws to determine the detection capabilities.” (Author), 4 refs.Google Scholar
- 1974–382.Felix, M. P., “Laser-Generated Ultrasonic Beams,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238, 224–240. “A device has been developed which uses a Q-switched laser pulse to produce a plane compressive stress pulse or a slowly decaying sinusoidal stress wave train in any solid or liquid material. The device utilizes a thin liquid layer to totally absorb the laser pulse and generate a stress pulse by rapid thermal expansion. Compressive stress pulses of 200 nanosecond duration and up to 5 kilobars amplitude have been obtained. Wave trains of about 30 cycle duration and 1/4 kilobar amplitude (peak-to-peak in typical solids) have been obtained at frequencies between 1–25 MHz. Stress amplitudes may be varied by filtering the incident laser radiation. This device should prove useful wherever large amplitude stress pulses or large amplitude sinusoidal wave trains are required—such as in nondestructive testing.” (Author)Google Scholar
- 1974–383.Meyer, P., “Ultrasonic Procedures for Predicting Adhesive Bond Strength,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238; 340–351. “Theoretical wave propagation models that treat ultrasonic wave interaction with an adhesively bonded system have been developed. These models allow the selection of appropriate ultrasonic transducers for bond inspection analysis. Such problems as a variation in bondline thickness, the presence of density gradients in the adhesive bond and improper surface preparation are treated in detail. Preliminary results indicate that the potential for success appears quite high for obtaining a correlation between a bond performance parameter and some specific ultrasonic test parameter.” (Author)Google Scholar
- 1974–384.Yee, B. G. W., “Applicability of Ultrasonic Resonance Spectroscopy to NDE of Adhesive Bonds,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238, 352–371. “Work being done at General Dynamics involving computerized signal processing of ultrasonic wave forms from metals, laminates and composites is discussed. The method has application for materials characterization and defect detection. A Hewlett-Packard 2100A digital computer was included into a laboratory tool for the signal processing described. The signal processing system includes an ultrasonic puiser, broad-band piezoelectric transducer, stepless gate oscilloscope, display scanner, and computer interface converter channels. Digitized wave forms are filtered and Fourier transformed by computer sof-ware and then displayed on an X-Y grid. A detailed description of wave-form digitization Fourier transforms, signal convolution and interpretation of results will be presented. The applicability of the computerized scheme to crack width detection, acoustic impedance determination, partial bond characterization and sound velocity measurements will be discussed. The prospective use for measuring the strength of bonded materials will also be discussed.” (Author)Google Scholar
- 1975–385.Cohen, E. R., “Analysis of Ultrasonic Scattering from Simply Shaped Objects,” Proc. of the ARPA/AFML Review of Quant. NDE, AFML-TR-75–212, 47–55. The mathematics of acoustic wave scattering from spheres and spheroids is developed.Google Scholar
- 1975–386.Krumhansl, J. A., “Basic Theory of Ultrasonic Scattering by Defects: Numerical Studies and Features for Experimental Application,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 57–66. The author summarizes his theoretical work on scattering of ultrasound by defects. An integral equation governing the scattering by an arbitrary shaped flaw is used. 3 refs.Google Scholar
- 1975–387.Packman, P. F. and Coyne, E. J., “Defect Characterization by Spatial Distribution of Ultrasonic Scattered Energy,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 129–146. Essentially the same as (1975–373).Google Scholar
- 1975–388.Sachse, W., “Scattering of Ultrasonic Pulses from Cylindrical Inclusions in Elastic Solids,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 147–168. A data collection and analysis system is presented. The angular and frequency-dependent scattering from imbedded cylinders is studied. The author performs the important task of identifying the received signals with the probable ray paths of the ultrasound. 8 refs.Google Scholar
- 1975–389.Couchman, J., “Digital Measurements of Scattering from Spheroids and Flat-Bottom Holes,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 169–194. Essentially the same as (1975–371).Google Scholar
- 1975–390.Tittmann, B., “Comparison of Theory and Experiment for Ultrasonic Scattering from Spherical and Flat Bottom Cavities,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 195–217. Essentially the same as (1975–374).Google Scholar
- 1975–391.Adler, L., “Angular Dependence of Ultrasonic Waves Scattered from Flat Bottom Holes,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 219–245. Essentially the same as (1975–372).Google Scholar
- 1975–392.White, R., “Surface Acoustic Wave Filters for Real Time Processing of Ultrasonic Signals,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 321–341. An expanded version of (1975–370). A clearly written and detailed explanation of how a SAW filter may be used for deconvolution.Google Scholar
- 1975–393.Mucciardi, A. N., “Adaptive Learning Network Approach to Defect Characterization,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 363–383. The feasibility of employing pattern recognition techniques to ultrasonic NDE is assessed. A data collection system is described and an adaptive learning network (ALN) is presented. The ALN flat-bottom hole classifier is found to be extremely accurate, 20 refs.Google Scholar
- 1975–394.Forsen, G., “Interactive Pattern Analysis and Recognition,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 385–398. The general approach of applying pattern analysis and recognition to NDE is discussed. 2 refs.Google Scholar
- 1975–395.Maxfield, B., “Optimization and Application of Electrodynamic Ultrasonic Wave Transducers,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 399–412. Essentially the same as (1975–369).Google Scholar
- 1975–396.Thomas, R., “Acoustic Surface Wave Generation with Electromagnetic Transducers,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 413–428. The author has extended the technique of EMAT-generated surface waves to frequencies in the MHz range (typically 4.5–10 MHz). The possibility of extending the range to 40 MHz seems to be good if the coil can be placed near enough to the sample surface.Google Scholar
- 1975–397.Frost, H. M. and Szabo, T. L., “Transducers Applied to Measurements of Velocity Dispersion of Acoustic Surface Waves,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 429–450. Wedge transducers, comb transducers, and flat cable and hand wound EMATS were used to measure surface wave dispersion. Results of the experiments are presented. 2 refs.Google Scholar
- 1975–398.Lakin, K., “Piezoelectric Transducers for Quantitative NDE,” Proc. ARPA/AFML Rev. of Quant. NDE,” AFML-TR-75–212, 463–478. A somewhat expanded version of (1975–368).Google Scholar
- 1975–399.Alers, G. and Graham, L., “Ultrasonic Wave Interactions with Interfaces,” Proc. ARPA/AFML Rev. Quant. NDE, AFML-TR-75–212, 579–593. Essentially the same as (1975–377).Google Scholar
- 1975–400.Rose, J., “Attenuation Influences in Adhesive Bond Modeling,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 595–611. Essentially the same as (1975–378).Google Scholar
- 1975–401.Seydel, J. A., “Methods Development for Nondestructive Measurement of Bond Strength in Adhesively Bonded Structures,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 613–630. The author uses an equivalent-time sampling and digitization system to acquire pulse-echo data from adhesive bonds. Attempts are made to characterize adhesive bond strength by a measurement of ultrasonic reflectivity as a function of frequency. 8 refs.Google Scholar
- 1975–402.Szabo, T., “Residual Stress Measurements from Surface Wave Velocity Dispersion,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 749–767. A method of inferring a subsurface residual stress gradient from surface wave dispersion data is presented. The techniques involve an inverse Laplace transformation of normalized dispersion data. 5 refs.Google Scholar
- 1975–403.Richardson, J., “Deducing Subsurface Property Gradients from Surface Wave Dispersion Data,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 769–790. Two situations are analyzed: (1) the dense data case, in which dispersion data are assumed to be available for all wavelengths, and (2) the sparse data case. An estimation theory approach is used to give the most probable subsurface gradient.Google Scholar
- 1976–404.Ulrych, T. J. and Clayton, R. W., “Time Series Modelling and Maximum Entropy,” Physics of the Earth and Planetary Interiors 12, (2/3), 188–200. “This paper briefly reviews the principles of maximum entropy spectral analysis and the closely related problem of autoregressive time series modelling. The important aspect of model identification is discussed with particular emphasis on the representation of harmonic processes with noise in terms of autoregressive moving-average models. It is shown that this representation leads to a spectral estimator proposed by Pisarenko in 1973.” (Author), 35 refs.Google Scholar
- 1976–405.Thompson, D. O., editor of Interdisciplinary Program for Quantitative Flaw Definition-Special Report Second Year Effort, Report for ARPA/ AFML under Contract F33615–74-C-5180. “The technical results of the second year of effort sponsored by the ARPA/AFML Center for Advanced NDE . . . are assembled in this report. They are grouped into three projects . . . (1) Flaw Characterization by Ultrasonic Techniques - electromagnetic transducers - characterization of NDE transducers - signal processing with SAW devices - high frequency ultrasonics - adaptive learning - sample preparation - fundamental scattering studies – standards - flaw detection in ceramics (2) Measurement of Strength Related Properties - adhesive bond strength - strength of composites (3) Nondestructive Measurement of Residual Stress in Metals - inference from harmonic generation - inference from efficiency of the electromagnetic generation of ultrasound . . .” (Editor).Google Scholar
- 1976–406.Thompson, R. B. and Fortunko, C. M., “Optimization of Electromagnetic Transducer Systems,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 1–19. The electronics and coil designs are optimized to provide the maximum signal to noise ratio. 13 refs.Google Scholar
- 1976–407.Lakin, K. M., “Characterization of NDE Transducers,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 30–43. Field pattern measurements are made utilizing the system described in previous publications. S-parameters are introduced as a “convenient means of describing devices involving transmission line type behavior.” 11 refs.Google Scholar
- 1976–408.White, R. M., “Signal Processing with SAW Devices,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 44–99. An update on the author’s work with SAW inverse filters.Google Scholar
- 1976–409.Elsley, R. K., “Quantitative Estimation of Properties of Ultrasonic Scatterers,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 63–86. The author describes how a data base of theoretical and ultrasonic scattering results was assembled. The data are to be used to train on adaptive learning network. “Some efforts were also directed toward investigating simple, non-adaptive learning techniques for inferring at least the size of the scattering object from the scattering data.” 2 refs.Google Scholar
- 1976–410.Mucciardi, A. N., “Application of Adaptive Learning Networks to NDE Methods,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr, Effort, 87–88. Describes the objectives of a project to model flaw characteristics obtained from theoretical ultrasonic scattering waveforms via adaptive learning decision algorithms.Google Scholar
- 1976–411.Krumhansl, J. A., “Theoretical Studies of Ultrasonic Scattering and Defects,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 102–122. The regions of applicability and validity of the Born approximation are determined. Other approximations (static, quasistatic) are evaluated. Work on scattering from flat cracks is detailed. 6 refs.Google Scholar
- 1976–412.Tittmann, B. R., “Measurements of Scattering of Ultrasound by Ellipsoidal Cavities,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 123–139. Scattering from ellipsoidal cavities is experimentally investigated. A contact method is utilized with the cavity at the center of a “doorknob” shaped sample. Incident longitudinal and shear waves are used. 1 ref.Google Scholar
- 1976–413.Adler, L. and Lewis, D. K., “Models for the Frequency Dependence of Ultrasonic Scattering from Real Flaws,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 140–166. “Scattering of elastic waves at flaws embedded in titanium was analyzed by measuring frequency and angular dependence of the scattered intensity pattern. This scattered intensity pattern was also calculated from two existing theories: (1) Keller’s geometrical theory of diffraction, which was solved for two-dimensional, crack-like flaws of circular and elliptical symmetries; (2) “Born approximation,” a scattering theory (introduced by Krumhansl et al., Cornell) for the spherical oblate and prolate spheroidal cavities. The experimental result was favorable compared to theory.” (Authors)Google Scholar
- 1976–414.Evans, A. G., Tittmann, B. R., Kino, G. S., and Khuri-Yakub, P. T., “Ultrasonic Flaw Detection in Ceramics,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 177–209. A high frequency (200 MHz) ultrasonic system is described. Techniques for accurate attenuation measurements have been made. Microstructure and scattering from defects have been studied. 7 refs.Google Scholar
- 1976–415.Alers, G. A. and Thompson, R. B., “Trapped Acoustic Modes for Adhesive Strength Determination,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 215–237. “The experiments discussed in this report were designed to consider the case in which the acoustic energy propagates parallel to the metal adhesive interface (of an adhesive bond) so that small differences in the boundary conditions could accumulate over a large interaction distance.” (Author), 6 refs.Google Scholar
- 1976–416.Flynn, P. L., “Cohesive Strength Prediction of Adhesive Joints,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 238–263. “An analytical study has been carried out to derive the acoustic spectral response of an attenuating adhesive bondline in terms of the physical properties of the adhesive . . . Experimental verification of the derived correlations was provided by systematically varying the properties of Chemlok 304, . . . correlated well Vith the ultrasonic amplitude ratio, sound velocity, attenuation coefficient and resonance depth. Correlation was not evident between resonance quality and strength because the sound velocity and attenuation of the adhesive were inversely related.” (Author), 6 refs.Google Scholar
- 1976–417.Rose, J. L. and Thomas, G. H., “Ultrasonic Attenuation Effects Associated with the Metal to Composite Adhesive Bond Problem,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 321–342. “Two different composite modeling approaches were used in this study. The first considered a 5-layer composite with the interfacial reflection caused by a very thin epoxy layer between composite layers. The second model consisted of an area discontinuity factor between each composite layer that accounted for the reflection factor at the interface. . . . The effect of composite masking was not significant in the 0–7 MHz range. After 7 MHz, however, the composite masking begins to show some significant effects, the effects however still being separable from the surface preparation or bond quality information.” (Author), 5 refs.Google Scholar
- 1977–418.Thompson, D. O., editor of Interdisciplinary Program for Quantitative Flaw Definition-Special Report Third Year Effort, Report for ARPA/AFML under Contract F33615–74-C-5180. “This report presents technical summaries of the various research tasks that have been pursued in the third year of effort by the ARPA/AFML Center for Advanced NDE. . . . They are grouped into two projects: (1) Flaw Characterization by Ultrasonic Techniques - electromagnetic and piezoelectric transducers - signal processing (SAW and CCD) - sample preparation - fundamental scattering studies (experimental and theoretical) imaging - adaptive learning - inversion techniques - failure prediction in ceramics - detection and characterization of surface flaws (2) Measurement of Strength Related Properties - adhesively bonded materials - composite materials - residual stress”Google Scholar
- 1977–419.Lakin, K. M. and Strand, T., “Characterization of NDE Transducers,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 21–41. “The problem of characterizing NDE transducers has been approached from two directions. First, the radiation pattern of the transducer has been analyzed in terms of Fourier transform reconstructions that yield information about the magnitude and phase of the fields anywhere in the region beyond the very near field. . . . The program (also) resulted in a simple but concise method for modelling the transducers as two-part hybrid networks ...” (Authors), 10 refs.Google Scholar
- 1977–420.White, R. M., “Signal Processing Research in Connection with Ultrasonics in Non-Destructive Testing,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 43–58. An analog data acquisition is described using a change coupled device (CCD) video delay line. A fast clock is used during acquisition; a slow clock for readout. Also a CCD transversal filter is used for matched filtering.Google Scholar
- 1977–421.Krumhansl, J. A., “Development and Application of Ultrasonic Scattering Theory to Non-Destructive Evaluation—Three Year Summary,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 64–69. A summary of the following work is presented. “(a) Careful examination of the general long wave limit in order to determine the maximum number of independent defect parameters which can be determined from scattering data. (b) Long wave and high frequency limits of scattering by cracks. (The Born approximation is not well defined for cracks.) (c) Addressing the ‘inverse’ problem. (d) Attempts to obtain an ‘exact’ (calibration) scattering solution for a few spheroidal geometries, to complete evaluation of Born approximation errors.” (Author), 19 refs.Google Scholar
- 1977–422.Domany, E., “Utilization of Physical Features of Scattered Power for Defect Characterization,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 70–81. “The first Born approximation provides a useful means to study scattering of ultrasound by various defects. In particular, it seems to yield qualitatively good results for the scattered power when averaged over a range of frequencies. Features of the scattered power that have been discovered by this method are reviewed. A convenient way to summarize the scattering data, by numerical projections, was used to assemble a library of scattered power from various defects. Addressing the particular problem of an oblate spheroidal cavity, a step-by-step procedure to determine its orientation and shape is suggested. Areas of future development are indicated.” (Author), 10 refs.Google Scholar
- 1977–423.Tittmann, B. R., Elsley, R. K., Nadler, H., and Cohen, E. R., “Experimental Measurements and Interpretation of Ultrasonic Scattering by Flaws,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 82–121. “The objective of this investigation was to develop procedures for deducing key geometric features of flaws from the details of the ultrasonic scattered fields, and, in particular, those features necessary for the evaluation against quantitative accept/reject criteria derived from fracture mechanics. To accomplish this objective, the investigation sought to correlate flaw characteristics such as size, shape, orientation and content of the flaw with the absolute value of scattered power and its variation with scattering angle and ultrasonic frequency, to verify theoretical scattering models developed by Krumhansl et al. (this report), and to lay the basis for inversion procedures developed by Mucciardi (see this report) and Bleistein (see this report).” (Author), 14 refs. (“This report” refers to Ref. 418.)Google Scholar
- 1977–424.Adler, L., “Identification of Flaws from Scattered Ultrasonic Fields as Measured at a Planar Surface,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 122–158. “The objective of this investigation was to correlate ultrasonic scattering data—such as the variation of scattered power with angle and frequency, mode conversion, etc.—to characteristics of a flaw in solids such as size, shape, and orientation by using flat samples and an immersed system.” (Author), 10 refs.Google Scholar
- 1977–425.Kino, G. S., “New Techniques for Acoustic Nondestructive Testing,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 159–175. A phased array imaging system is described. The circuitry and inverse filter system are useful to anyone constructing an ultrasonic system (quantitative or imaging).Google Scholar
- 1977–426.Mucciardi, A. N., Shankar, R., Shaley, M. F., and Johnson, M. D., “Application of Adaptive Learning Networks to NDE Methods,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 176–231. Adaptive learning networks to the following problems. - measurement of the size and acoustic impedance of spherical defects from the analysis of theoretically scattered waveforms. - actual scattering from spherical defects. - estimate the size and orientation of spheroidal defects from analysis of the Born approximation model. 6 refs.Google Scholar
- 1977–427.Bleistein, N. and Cohen, J., “Application of a New Inverse Method for Nondestructive Evaluation,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 232–246. “The application of a new inverse method to nondestructive evaluation is described. In particular, detection of a small hole in an otherwise homogeneous solid is discussed. The scattering of an acoustic probe by the hole is considered. It is shown that the scattered wave is proportional to the Fourier transform of the characteristic function of the domain occupied by the hole. The characteristic function is equal to unity in that domain and zero outside. Thus, knowledge of this function characterizes the domain. The basic result is derived under the assumption that the scatterer is small — allowing use of the Born approximation — and “far” from the surface of the solid. Some features of aperture limited — band limited and aspect angle limited — observations are discussed. The applicability of this inverse method to non-destructive evaluation is demonstrated by this preliminary analysis.” (Authors), 12 refs.Google Scholar
- 1977–428.Kino, G. S., Khuri-Yakub, B. T., Tittmann, B. R., Ahlberg, L., Evans, A. G., Biswas, R., and Fulrath, R., “Ultrasonic Failure Prediction in Ceramics,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 247–266. Defect characterization in the size range (10–100 micrometer) in structural ceramics was performed. High frequency techniques (200 MHz) were employed. A new ultrasonic technology, based on ZnO was developed as part of the problem. 8 refs.Google Scholar
- 1977–429.Alers, G. A. and Elsley, R. K., “NDE Techniques for Measuring the Strength of Adhesion,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort,” 271–285. “It has been the objective of this study to find ultrasonic techniques that can give a quantitative measure of the status of the metal to adhesive interface so that the adhesion strength of an adhesive bond could be predicted. ... it is possible to predict the approximate strength of the adhesive bond from a measurement of the splitting of the lowest standing wave resonance in the adherends.” (Authors), 7 refs.Google Scholar
- 1977–430.Flynn, P. L. and Henslee, S. P., “Cohesive Bond Strength Prediction, FM-400 a Realistic Adhesive System,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 286–307. “... Scattering analysis was applied to an adhesive layer and provided a basis for choosing measureable ultrasonic parameters that characterized the acoustic properties of the layer. This method was applied to simple adhesive systems with good results, but found some problems in general application. The largest problem in the scrimmed adhesive was entrapment of small voids in the scrim pattern. The small voids affected the attenuation measurements, but did not affect the cohesive strengths.” (Authors), 8 refs.Google Scholar
- 1977–431.Thompson, D. O., Proceedings of the ARPA/AFML Review of Progress in Quantitative NDE, Tech. Rpt. AFML-TR-77–44. These edited transcripts contain information relating to quantitative NDE. Included are summaries of work on: Adhesives and composites New materials and techniques Measurement of internal stress Fundamentals of acoustic emission Signal acquisition and processing Defect characterization - fundamentals (experimental and theoretical) and techniques. “In addition a Mini-Symposium is presented related to Advances in Electromagnetic Transducers.” (Editor)Google Scholar
- 1977–432.Alers, G. A., “Trapped Acoustic Modes for Adhesive Strength Determination,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 52–58. “In order to extend the time and distance over which an ultrasonic wave can interact with the strength determining layer at a metal to adhesive interface, we have considered the acoustic wave modes that propagate parallel to the interface in the plane of a sandwich type adhesive bond between two metal plates. A detailed mathematical analysis of these bound modes was made with special attention to the role played by the boundary conditions at the adhesive to metal interface so that the frequencies and modes that are most sensitive to the bounding conditions could be predicted. Experiments to verify these predictions were carried out using surface waves launched into the adhesive layer from the external metal plates and by current carrying wires embedded in the adhesive subjected to an external, static magnetic field. The theoretical analysis also predicted that the fundamental thickness mode of vibration of the entire sandwich structure should also exhibit a sensitivity to the boundary conditions. This was studied experimentally by taking the Fourier transform of low frequency echos reflected from the structure.” (Author)Google Scholar
- 1977–433.Flynn, P. L., “Cohesive Strength Prediction of Adhesive Joints,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 59–65. “An analytical study was carried out to determine the influence of changes in bondline properties on measurable ultrasonic parameters in both the time and frequency domains. An experimental study was conducted in which the adhesive properties were varied by mixing a paste adhesive in different ratios of resin and hardener. The properties of the adhesive bondlines were measured in-situ with high frequency, broad-band ultrasonics. Physical properties extracted from the ultrasonic data included the sound velocity, acoustic impedance and the attenuation of the adhesive layer. The expected correlations were seen between the NDE parameters identified by the analytical study and the strength and stiffness of the bonded specimens.” (Author), 3 refs.Google Scholar
- 1977–434.Buckley, M. J. and Raney, J. M., “The Use of Continuous Wave Ultrasonic Spectroscopy for Adhesive-Bond Evaluation,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 66–73. “For certain NDE applications, the use of CW ultrasonic spectroscopy to acquire ultrasonic transmission and reflection data has several advantages over pulse techniques. The specific system currently used to record amplitude and phase as a function of frequency over the range of 20 KHz to 20 MHz will be discussed. In addition, theoretical calculations of the ultrasonic spectra for adhesively bonded structures will be presented along with initial results obtained in fitting the theoretical calculations to the experimental data in order to determine the acoustic properties of the adhesive layer.” (Author), 2 refs.Google Scholar
- 1977–435.Evans, A. G., “Ultrasonic Flaw Detection in Ceramics,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 74–77. “A high frequency ultrasonic approach for determining defects in ceramic materials (in the size range required for failure prediction) has been outlined. A 200 MHz A-scan device pulsed with a short (2 ns) pulse has been constructed and shown to have a good dynamic range (70 dB) and a depth resolution of at least 25 microm. A B-scan system for defect detection studies has also been developed and is ready for use. Techniques for accurate attenuation measurements in ceramics have been developed and automated. Preliminary data have also been obtained on a range of ceramic polycrystals. Calculations of the scattering from defects in ceramics, and of bond losses in thin gold foils, have been used in cylinders with the attenuation data to predict typical defect detectabilities. These calculations predict that defects in the size range 20–100 microm. should be detectable (with the present transducers) in fully-dense, fine-grained ceramics. Preliminary defect detection studies have confirmed that defects at least as small as 100 microm. are readily detectable in these materials.” (Authors)Google Scholar
- 1977–436.Lakin, K. M., “Characterization of NDE Transducers,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 116–122. “A system for characterizing NDE transducers has been implemented which involves both electrical circuit modeling and measurements of the amplitude and phase of the radiation patterns. The field pattern measurements allow a determination of the field at the transducer surface as well as at locations distant from the transducer. The technique is also adaptable to characterizing scattering surfaces treated as apparent sources. The electrical characterization centers around a network model involving a hybrid set of S-parameters. Using simple and readily available references, the four parameters of the transducer may be determined and then used to quantitively predict the transducer performance in scattering experiments. In its simplest form the technique uses water bath experiments and scattering off the transducer surface.” (Author)Google Scholar
- 1977–437.Szabo, T. L., “Surface Acoustic V/ave Electromagnetic Transducer Modeling and Design for NDE Applications,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 128–132. “Recent progress in SAW electromagnetic transducer (EMT) modeling and fabrication techniques have greatly increased EMT versatility for NDE applications. Unlike other types of SAW NDE transducers that suffer from variability in manufacture and coupling conditions, virtually identical EMT1s can be made that have predictable characteristics. During the past year we have developed a new equivalent circuit model for the noncontact EMT that describes both its acoustical and electrical characteristics. This model is useful for design and for assessing the effects of electrical matching and transduction on different materials. Perhaps the most striking result of the model is the similarity in frequency response between the meander line SAW EMT and the SAW interdigital transducer. For conventional EMT’s, design is simple and in excellent agreement with experiment. By modification of transducer geometry, as with IDT’s, more advanced frequency response shapes can be realized. This result implies that for SAW EMT’s signal processing functions can be combined with transduction for NDE applications.” (Author), 10 refs.Google Scholar
- 1977–438.Maxfield, B. W., “Optimization and Application of Electrodynamic Acoustic Wave Transducers,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 133–135. “We have used electromagnetic acoustic-wave transducers (EMATs) to measure the intensity distribution of shear ultrasonic waves scattered by a cylindrical flaw and a conventional flat-bottomed hole. Results are in reasonable qualitative agreement with the behavior expected for these scattering arrangements. Quantitative measurements, however, have proven very difficult to obtain because of fundamental problems in providing adequate shielding for the receiver coil while avoiding distortion of the drive field. Our experimental work has defined the problem areas and in most cases suggested solutions. It now seems quite probable that other work, both in this program and outside, may yield definitive solutions to the problems that we have identified so that in the near future it may be possible to have quantitative shear wave scattering information from scanned EMAT measurements.” (Author)Google Scholar
- 1977–439.Moran, J. J., “Characteristics and Applications of Electromagnetic Surface Wave Transducers,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 136–141. “The steerability and relative generation efficiency of bulk acoustic waves generated by a meander line EMAT in aluminum have been determined. The frequency dependence of the propagation angle relative to the surface was found to agree well with theory. Efficiency for shear-wave generation (frequency range, 5–9 MHz) was about 4 dB per conversion less than the Rayleigh-wave generation efficiency at 4.6 MHz, and for longitudinal waves (frequency range, 10–24 MHz) about 10 dB less. A second effort to achieve piezoelectric SAW device signal processing capabilities with EMAT designs has shown that a pulse compression device is completely feasible. We have demonstrated that it is possible to compress a 3.5 ysec (2–6 MHz) chirp signal to a 0.25 ysec pulse. Possible applications will be discussed.” (Author)Google Scholar
- 1977–440.Thompson, R. B. and Fortunko, C. M., “Optimization of Electromagnetic Transducer Systems,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-44, 142–147. “The results of a program to realize maximum dynamic ranges with lightweight electromagnetic transducers suitable for hand-held use is described. Transducers were constructed using compact samarium-cobalt permanent magnets and: (1) spiral coils for generating axially polarized shear waves, (2) masked coils for generating plane polarized shear waves, and (3) meander coils for generating surface waves. A high power, line generator was constructed which uses a spark-gap to switch currents of several hundred amperes in either single pulse or tone burst mode of operation. A new transformer coupling network and a broadband, low noise preamplifier have been demonstrated for an overall 30 dB increase in sensitivity. Dynamic ranges as high as 80 dB were obtained in the tone burst mode (Δf/f ~ 10%). Applications of these transducers to problems of the Army and EPRI will be briefly discussed.” (Author), 7 refs.Google Scholar
- 1977–441.White, R. M., “Signal Processing with Surface Acoustic Wave Devices,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 148–153. “A surface acoustic wave (SAW) filter was designed and constructed having a response inverse to that of a simulated NDT system. Further testing of this filter was undertaken with the aim of characterizing the filter more accurately. A redesign of the filter to include an input transducer having less loss was then carried out. It appears that the use of a two-pair of three-pair input IDT is advantageous, and a filter incorporating such a transducer is now being fabricated for use with the simulated NDT system (5 MHz PZT transducer cemented onto an aluminum block). With this filter, determination is to be made of all the relevant electrical characteristics, as well as determination of the minimum spatial resolution obtainable at the filter output when two closely-spaced impedance discontinuities produce reflection.” (Author), 3 refs.Google Scholar
- 1978–442.Haines, N. F., Bell, J. C, and Mclntyre, P. J., “The Application of Broadband Ultrasonic Spectroscopy to the Study of Layered Media,” J. Acoust. Soc., Am. 64 (6), 1645–1663. “An investigation has been made of the frequency dependence of amplitude and phase information when broadband ultrasonic pulses, in the region 1–30 MHz, are reflected from layered targets. An on line computer performing Fourier analysis of sampled ultrasonic pulses allowed both amplitude and phase information to be studied. Layers of various acoustic impedances, velocities, and attenuation have been investigated, and in particular, layers of magnetite grown on mild steel. In all cases excellent agreement between experiment and theory has been achieved. The possible use of the techniques of deconvolution has also been considered for the measurement of the thickness of layers. The methods developed have found application in the problem of determining the thickness of a corrosion layer on the inside surface of a component where access can only be gained through the outer surface.” (Authors), 64 refs.Google Scholar
- 1977–443.Heyman, J., “A Non-Phase Sensitive Transducer for Ultrasonics,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 154–156. The phase-insensitive nature of a CsS acoustoelectric converter is discussed for applications in NDE.Google Scholar
- 1977–444.Krumhansl, J. A., “Interpretation of Ultrasonic Scattering Measurements by Various Flaws from Theoretical Studies,” Proc. ARPA.AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 164–172. “From a review and extension of the general theory of ultrasonic scattering by defects in elastic media we have developed computer programs and approximation methods for analyzing experimental scattering data. Few exact theoretical expressions are available, but significant information can be obtained from the “Born approximation,” the quasi-static approximation, and the exact long wave limit. Computed results for spheres and spheroids (prolate and oblate), for both longitudinal and transverse incident and scattered waves will be presented. In addition, we explore several methods for visual and graphical presentation of the analytical results for most convenient use in test situations.” (Author), 6 refs.Google Scholar
- 1977–445.Tittmann, B. R., “Scattering of Ultrasound by Ellipsoidal Cavities,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 173–179. “Experimental results have been compared with theory for ellipsoidal and spherical cavities embedded in titanium alloy by the diffusion bonding process. The measurements comprised the cases of incident longitudinal and shear waves including mode conversion. Whenever possible, comparisons were performed with the results of exact theory and those of the Born approximation. The Born approximation was found useful in the back scattering directions for low ka values (k is the wave vector of the sound wave and a is the radius of the scatterer). In the experiments, a reciprocity relation was discovered which should prove very useful in further studies: The same angular dependence is obtained in mode conversion when the mode of the incident and scattered wave is interchanged. This result has now been corroborated by both the exact theory and the Born approximation. The results are discussed in the context of failure prediction.” (Author), 4 refs.Google Scholar
- 1977–446.Adler, L. and Lewis, K., “Models for the Frequency Dependence of Ultrasonic Scattering from Real Flaws,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 180–186. “Scattering of elastic waves at flaws embedded in titanium was analyzed by measuring frequency and angular dependence of the scattered intensity pattern. This scattered intensity pattern was also calculated from two existing theories: (1) Keller’s geometrical theory of diffraction, which was solved for two-dimensional crack-like flaws of circular and elliptical symmetries; (2) “Born approximation,” a scattering theory (introduced by Krumhansl et al., Cornell) for the spherical oblate and prolate spheroidal cavities. The experimental result was favorably compared to theory.” (Authors)Google Scholar
- 1977–447.Mucciardi, A. N., “Measurement of Subsurface Fatigue Crack Size Using Nonlinear Adaptive Learning,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 194–199. “A new NDE nonlinear signal processing system has been developed to detect and measure small, subsurface fatigue cracks. The system synthesized from nondestructive evaluation (NDE) waveform parameter inputs is capable of detecting and measuring quantitatively subsurface fatigue cracks in the size range of 0 to 279 mils to within 70 percent of their nominally characterized lengths. Previous investigations had achieved a 50 percent detection rate for cracks larger than 30 mils. However, the fatigue crack measurement system reported herein is the first known fatigue crack NDE system capable of detection and measurement for this wide range.” (Author)Google Scholar
- 1977–448.Rose, J. L., Eisenstein, B., Fehlauer, J., and Avioli, M., “Defect Characterization—Fundamental Flaw Classification Solution Potential,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 200–207. “Emphasis in the paper will be placed on a work description and analysis associated with a flaw classification problem of discriminating between ultrasonic signals that have been reflected from elliptical and circular side drilled electro discharge machined slots in a steel block. The flaw types used in this experiment are several elliptical holes with eccentricities, from .15 to 1.0. The signals are sampled at a 100 MHz rate and quantized with an 8 bit word length. The signal processing is performed on a PDP 11/05 mini-computer. . . . Results obtained thus far indicate that for minor diameter to major diameter ratios e in excess of 0.7, discrimination between elliptical and circular flaws is very difficult. For e less than 0.3, discrimination is easy. Consequently, the feature extraction and pattern classification techniques have been concentrated on e in the range 0.3 to 0.7 in order to establish the efficacy of the research protocol.” (Authors)Google Scholar
- 1978–449.Thompson, D. O., Proceedings of the ARPA/AFML Review of Progress in Quantitative NDE, Tech. Rpt. AFML-TR-78–55. “The edited transcripts of the ARPA/AFML Review of Quantitative NDE . . . are presented in this document.” (Editor) Topics covered in the review include Flaw Characterization by Quantitative Ultrasonics - long wave scattering - experimental measurements - use of physical features of scattered power for defect characterization - inversion methods Minisymposium on Scattering Theories New Techniques and Phenomena - prediction of remaining life of fatigue damaged samples - exoelectron emission - measurement of stress profiles - ultrasonic tomography – imaging - ultrasonic transducers - acoustic emission – penetrants NDE for Advanced Materials - fracture mechanics - bond strength Reliability of Structural Ceramics - high frequency ultrasonics - ultrasonic microscopy New Technology - electronic equipment – transducers – standards – imaging - adhesive bondsGoogle Scholar
- 1978–450.Gubernatis, J. E., “Long Wave Scattering of Elastic Waves from Volumetric and Crack-Like Defects of Simple Shapes,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 21–25. “The development of several approximations appears to permit accurate and practical calculations of the scattering of elastic waves from volumetric and crack-like defects of simple shapes if the wavelength of the incident wave is larger than the characteristic length of the shape. These approximations, which I call the quasi-static and extended quasi-static, use static solutions of defects in uniform strains to predict scattered (dynamic) fields. Since static solutions for several simple defect shapes (oblate and prolate spheroid, ellipsoid, and circular and elliptical cracks) are available, scattering predictions are possible, and the results of such calculations are presented.” (Author), 10 refs.Google Scholar
- 1978–451.Tittmann, B. R. and Elsley, R. K., “Experimental Measurements and Interpretation of Ultrasonic Scattering by Flaws,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 26–35. “Experimental measurements have been carried out on the scattering of elastic waves from ellipsoidal and spherical cavities embedded in titanium alloy by the diffusion bonding process. The scattering data have been compared with calculations from exact theory and those from the Born approximation. The results allow the following conclusions: (1) the new concept of sample fabrication by the diffusion bonding process is proven to be successful, (2) the scattering data have been found to be a valuable test for the evaluation and refinement of scattering theories which treat scattering from ellipsoidal cavities on an approximate basis, (3) the scattering data provide a useful data base for use in developing scattering inversion techniques (i.e., deterministic, probabilistic, or adaptive schemes) from which quantitative properties of the scattering center can be rapidly extracted; (4) the work has provided a preliminary definition of the minimum quantity and type of data acquisition needed for a “smart” NDE system.” (Authors), 3 refs.Google Scholar
- 1978–452.Adler, L., Lewis, K., Szilas, P., and Fitting, D., “Identification of Flaws from Scattered Ultrasonic Fields as Measured at a Planar Surface,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 36–43. “Ultrasonic wave scattering from ellipsoidal and cylindrical cavities embedded in titanium was measured and analyzed with a newly designed signal processing system. Using an immersion system and samples with flat faces, the range of waves incident, at certain polar and azimuthal angles, was determined for both L-L and L-S scattering. Attempts were made to define key parameters from both amplitude and phase spectra for characterizing cavities. Results are compared to predictions of Born approximations (developed by Krumhansl et al. at Cornell) and to experimental results taken by a contact system (Tittmann et al. at Rockwell). A new (Keller type) theory for cracklike defects which includes mode conversion will also be presented.” (Authors), 2 refs.Google Scholar
- 1978–453.Domany, E., “Utilization of Physical Features of Scattered Power for Defect Characterization,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 44–49. “The first Born approximation provides a useful means to study scattering of ultrasound by various defects. In particular, it seems to yield qualitatively good results for the scattered power, when averaged over a range of frequencies. Features of the scattered power that have been discovered by this method will be reviewed. Closer study of some of these features leads to a step procedure to characterize an oblate spheroidal defect; to determine its orientation and shape. Procedures for extension to other shapes can also be given. Areas of future development will be indicated.” (Author), 10 refs.Google Scholar
- 1978–454.Shankar, R., Mucciardi, A. N., Whaley, M. F., and Johnson, M. D., “Inversion of Ultrasonic Scattering Data to Measure Defect Size, Orientation and Acoustic Properties,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 50–72. “Empirical solutions via the adaptive learning network methodology have been obtained to measure characteristics of three-dimensional defects (spherical and spheroidal) from the analysis of theoretically-modeled scattered waveforms. The solutions have been successfully applied to measure defects from actually observed ultrasonic scattering data. Spherical voids and inclusion in Ti-6–4, varying in diameter from 0.02 cm to 0.12 cm, and varying in acoustic impedance ratio (with respect to the host alloy (Ti-6–4) from zero for air cavities to four for tungsten-carbide inclusions, can be directly measured via: (i) The phase cepstrum — which yields an unambiguous measurement of defect diameter and is independent of its acoustic impedance ratio. (ii) Adaptive Learning Networks (ALN) — synthesized from the amplitude spectrum and which yield accurate measurements of defect diameter and the acoustic impedance ratio of the included material. The two empirical solutions, synthesized from the scattering data from an exact model for spheres, yield similar accurate results when applied to actual scattering observed from the defects.” (Authors), 6 refs.Google Scholar
- 1978–455.Bleistein, N. and Cohen, J. K., “Application of Geometrical Diffraction Theory to Scattering by Cracks,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 102–107. “We formulate the inverse problem as an equation or system of equations in which one of the unknowns is a function which directly characterizes the irregularity to be determined. Under the assumption of small sized anomalies or small changes in media properties, our system reduces to a single linear integral equation for this “characteristic” function. In many cases of practical interest, this equation admits closed form solutions. Even under the constraints of practical limitations on the data, information about the irregularity can be deduced. As an example, we consider the case of a void in a solid probed by acoustic waves. We show how high frequency data can be directly processed to yield the actual shape of the anomaly in a region of the surface covered by specular reflection of the probe. In the low frequency case, we show how to directly process the data to yield the volume, centroid, and “products of inertia” of the void.” (Authors), 10 refs.Google Scholar
- 1978–456.Sachse, W., “Measurement of Phase and Group Velocities of Dispersive Waves in Solids,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 122–126. “The dispersion relation and the propagational speeds of waves in dispersive solids are determined by a newly developed technique in which the phase function of spectral analyzed broad band pulses is determined. The method is simpler and in agreement with the continuous wave-resonance technique. Application is made to ultrasonic stress waves and pulses propagating in fiber-reinforced composite materials.” (Author)Google Scholar
- 1978–457.Heyman, J. S., “A Phase Insensitive Ultrasonic Receiver,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 151–156. “A phase insensitive receiver transducer called an acousto-electric converter (AEC) is described and several applications to NDE are presented. Although phase information in ultrasonics is used for many sensitive material measurements, the phase signal may effectively result in noise under certain circumstances. When the propagating phase front is spacially variant and the acoustic receiver is larger than the acoustic wavelength, severe modulation of the resulting electrical signal occurs. Under these conditions, the electrical output of the transducer is a complicated superposition of incident waves of different phase and amplitude. These effects are particularly troublesome in applied studies such as NDE where non-flat and parallel inhomogeneous materials are investigated. To examine the application of the new receiver to NDE, comparison data is presented obtained under identical conditions for ultrasonic transmission through materials using conventional as well as AEC transducers. The materials investigated contain phantom flaws in both metals and composites. The results indicate that an AEC may be a useful device for material characterization.” (Authors), 11 refs.Google Scholar
- 1978–458.Kwan, S. H., White, R. M., and Müller, R. S., “Integrated Ultrasonic Transducer,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 157–160. “Ultrasonic transducers composed of integrated assemblies of double-diffused MOS transistors (DMOST) and thin-film piezoelectric transducing elements are described. The entire transducer is built on a single-crystal silicon wafer and offers a number of attractive features including: small size and correspondingly precise localization of the sensitive element, a response that can be predicted by relatively simple theory, a large bandwidth and possibility of producing arrays of sensors together with other signal-processing elements in a single processing sequence. The piezoelectric film (zinc oxide) is sputtered either in one gate region of a field effect transistor (making the “PIFET” structure) or adjacent to the gate electrode of a double-diffused MOS transistor (the “PI-DMOST” structure). The transducer may be excited in various ways: (1) in a thickness mode from the bare silicon surface opposite the piezoelectric-coated region; (2) in a flexural mode caused by bending the silicon wafer; (3) end excitation by surface motions either normal or transverse to the edge of the wafer; (4) by surface waves. Various of these modes are characterized by high sensitivity to strain, low conversion loss, large bandwidth, and good response at very low or very high frequencies.” (Authors)Google Scholar
- 1978–459.Alers, G. A., Elsley, R. K., and Flynn, P. L., “Bond Strength Measurements by Ultrasonic Spectroscopy,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 191–197. “During the current phase of the program, more reliable and statistically significant mechanical tests for the strength of an adhesively bonded joint have been developed and more accurate measurement techniques for extracting quantitative information from both the time domain and the frequency domain representations of the ultrasonic data have been found. As a result, measurements of the wave velocity and the attenuation in FM-400 adhesive sandwiched between sheets of aluminum alloy and subjected to different degrees of cure successfully predicted the final cohesive shear strength of the joints. Quantitative measurements of the standing wave resonant frequencies in aluminum-Chemlok 304 adhesive-aluminum sandwiches showed a strong correlation with the strength of adhesive joints prepared with weak adhesion at the metal to adhesive interfaces. By making many adhesive joint samples and testing their strengths specifically in the region interrogated by the ultrasound, the reliability of all the correlations between strength and ultrasonic measurements were greatly improved.” (Authors)Google Scholar
- 1978–460.Evans, A. G., “Overview of Reliability in Structural Ceramics,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 233–236. “The failure prediction requirements and the pertinent accept/reject criteria for structural ceramics are derived, and the available failure prediction techniques are examinedd, vis-a-vis the failure prediction relations, in order to highlight the capabilities and limitations of each technique. The need for additional techniques is thereby demonstrated. The capabilities of the ultrasonic technique are extensively evaluated in order to determine its ability to satisfy the deficiencies in the existing failure prediction repertoire. The prospects are shown to be very encouraging, but the results of several key studies must be awaited before defining the ultimate role of ultrasonic failure prediction techniques.” (Author)Google Scholar
- 1978–461.Kino, G. S., Khuri-Yakub, B. T., and Tittmann, B. R., “High Frequency Ultrasonics,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 237–240. “A high frequency 250 MHz A-scan system has been used for flaw detection. We have been able to detect 25–500 μm defects of different types (C, Si, SiC, BN, Fe, WC) in a Si
_{3}N4 plate. Since it is difficult to determine the defect type and size from the amplitude of the back-scattered signal, so we have carried out Fourier transforms of the back-scattered signal to obtain reflectivity as a function of frequency, and used that information to characterize the size and type of defect. Our early experiments have been with voids in glass and Si_{3}N4 and we are able to predict the size of the defects we detect.” (Authors), 1 ref.Google Scholar - 1978–462.White, R. M., “Programmable Filter for Ultrasonic NDE Systems,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 307–311. “Transversal filters based on the charge-coupled device (CCD) technology may be applied to processing received signals in an ultrasonic NDE system. Filters having a fixed response (fixed tap weightings) could be used to compensate for the characteristics of a given ultrasonic transducer. A more flexible arrangement allowing programmability employs a CCD delay line whose tap electrodes are accessible externally for weighting. The response of this device can be altered by changing a set of resistors mounted on a printed circuit board which can be plugged into a socket connected to the CCD. Proper response for a given ultrasonic transducer is obtained by plugging in the proper circuit board. Because present commercial CCD’s allowing programmability have clock frequencies too low for direct processing of ultrasonic NDE signals, the filter is preceded by a CCD video delay line which quickly stores the return signal and then outputs it more slowly for processing during the time between successive excitations of the ultrasonic transducer.” (Author)Google Scholar
- 1978–463.Furgason, E. S., Twyman, R. E., and Newhouse, V. L., “Deconvolution Processing for Flaw Signatures,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 312–318. “The ultimate resolution of all ultrasonic flaw detection systems is limited by transducer response. The system output actually contains detailed information about the target structure that has been masked by the transducer characteristics. This type of problem is common in all remote sensing applications and has been attacked by workers in several other fields. The output of any linear system can be modeled as the convolution of the target response and transducer response. For such a system the convolution process can be easily reversed to remove the effects of the transducer, yielding an accurate detailed image of the target. Unfortunately, it is well known that real systems have noisy outputs and that the presence of even relatively small amounts of noise make this deconvolution process impossible. Recently, ultrasonic flaw detection systems have been demonstrated which have extremely high output signal-to-noise ratios. For these systems it is possible to use estimation techniques in the deconvolution process to achieve a good approximation to the actual target response. Results are presented that demonstrate these techniques applied to both computer generated and experimental data. Coupling the deconvolution processing with feature extraction routines is shown to yield an order of magnitude increase in range resolution.” (Authors), 3 refs.Google Scholar
- 1978–464.Lakin, K. M., “Characterization Facility for NDE Transducers,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 319–325. “The characterization of NDE transducers involves an assessment of the bidirectional acousto electric conversion between electrical and acoustic terminals and an evaluation of the near and far-field radiation patterns. The internal details of the transducer are largely unknown and, consequently, the traditional techniques for analyzing the structures cannot be applied. Instead, the transducer may be characterized as a hybrid two port network whose parameters may be determined by relatively simple measurements taken at the electrical port when the acoustic loads are known. The radiation pattern involves measurement only in the region exterior to the transducer. There are several techniques which may be used to accomplish this task. Our approach has been to measure the acoustic field in the far-field region and then to reconstruct the field at the face of the transducer. Once we have the field at the transducer, an evaluation of the source may be readily determined from amplitude and phase contour plots or from gray scale or pseudo-color images.” (Author), 6 refs.Google Scholar
- 1978–465.Elsley, R. K., “Computer Aided Interpretation of NDE Signals,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 326–330. “In order to improve NDE reliability, it is important to recover as much as possible of the useful information in NDE waveforms. An on-line minicomputer is ideally suited to both the collection of data and the performance of sophisticated signal processing tasks. Using a variety of signal processing techniques, including windowing, self-normalization (of transducer properties and far-field diffraction effects), transformations (Fourier magnitude and phase transforms, autocorrelations, cepstra), feature extraction and pattern recognition, it has been possible to obtain information about very small defects, strength of adhesive bonds and acoustic emissions which are not available by conventional means. Examples of these various capabilities will be given.” (Author)Google Scholar
- 1978–466.Alers, G. A., Elsley, R. K., and Flynn, P. L., “Measurement of Strength of Adhesive Bonds,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-78–55, 365–370. “In order to predict the strength of an adhesive bond between two metal sheets, it is necessary to measure the physical state of the adhesive layer that mechanically joins the two pieces of metal. This requires rapidly performing a detailed analysis of the ultrasonic echos reflected from the entire structure when it is immersed in a water bath for a normal ultrasonic pulse-echo inspection. To achieve this result, computer operated ultrasonic inspection systems have been assembled and equipped with special signal processing routines so that particular features of the ultrasonic echo in both the time domain and the frequency domain can be extracted in a time short enough to meet the requirements of a production inspection system. Such features as the relative amplitude of the signals reflected from the top and bottom of the adhesive layer and the frequencies for which standing waves are excited in the adhesive and in the metal adherends are of particular interest for making the strength predictions. It is also important that the interrogating ultrasonic pulse be of very short time duration so that the echos from the various interfaces in the sandwich-like joint can be resolved in the time domain display. This requires the use of special high frequency pulse generators coupled to broad band transducers and amplifiers. Special procedures are also needed to insure the accuracy of the analog to digital conversion at the input to the computer and the subsequent transformations to and from the frequency domain.” (Authors)Google Scholar
- 1978–467.Busse, L. J., Miller, J. G., Yuhas, D. E., Mimbs, J. W., Weiss, A. N., and Sobel, B. E., “Phase Cancellation Effects: A Source of Attenuation Artifacts Eliminated by a CsS Acoustoelectric Receiver,” Ultrasound in Medicine, Vol. 3, Denis White, ed. Plenum Press, New York. “One salient problem associated with experiments designed to determine the attenuation coefficient of an inhomogeneous specimen is that of phase cancellation effects. Phase cancellation effects may occur if inhomo-geneities in the tissue distort the ultrasonic phasefronts presented to a spatially extended piezoelectric receiving transducer. When the wave-fronts incident upon a conventional piezoelectric receiver are distorted, the generated electrical signal would be expected to be degraded because of the phase sensitive nature of the receiver. Phase cancellation effects can induce artifacts in attenuation data which might be interpreted incorrectly as reflecting only the absorption and scattering properties of a specimen. The purpose of this report is threefold: i) to demonstrate the existence of phase cancellation effects and to show how these effects manifest themselves in measurements of the ultrasonic attenuation coefficient of tissue, ii) to show how phase cancellation effects associated with piezoelectric receivers can be reduced by appropriate choice of aperture size, and iii) to show how phase cancellation effects can be virtually eliminated by making use of an intensity sensitive ultrasonic receiver based upon the acoustoelectric effect—the coupling of acoustic energy to the system of charge carriers within a semiconducting crystal.” (Authors)Google Scholar
- 1976–468.Kraut, E. A.,”Applications of Elastic Waves to Electronic Devices, Nondestructive Evaluation and Seismology,” Proc. 1976 IEEE Ultrasonics Symposium. “Interactions between electrical engineers concerned with device applications of elastic wave propagation and workers in the fields of nondestructive evaluation, seismology, and mechanics can be mutually beneficial and rewarding. Recently, the National Science Foundation sponsored an interdisciplinary workshop to promote such interactions through discussions of research activities of current interest in each of these different fields. Areas where results in one field could contribute to progress in another were identified. Some examples include the use of surface acoustic wave correlators for flaw detection in NDE, application of new methods for time series analysis to ultrasonic and seismic data processing, fracture mechanics analogies in seismic source theory, and applications of new results in the theory of piezoelectric plate vibrations to oscillator and filter design. These and other examples of overlaps will be presented.” (Author), 92 refs.Google Scholar
- 1974–469.Weiler, J. F. and Giallorenzi, T. G., “Optical Detection of Acoustic Surface Waves in Layered Substrates: Theory and Experiment,” IEEE Trans. Son. Ultrason., SU-21 (3), 196–203. “Light diffraction by surface acoustic waves in layered media is theoretically analyzed. Experimental verification of the theory is presented for an SiO
_{2}film on LiNbO_{3}and a Ta_{2}O_{5}film on quarts.” (Author), 18 refs.Google Scholar - 1974–470.Hjellen, G. A., Andersen, J., and Sigelmann, R. A., “Computer-Aided Design of Ultrasonic Transducer Broadband Matching Networks,” IEEE Trans. Son. Ultrason., SU-21 (4), 302–304. “The application of computer-aided circuit design (CAD) for modifying the performance of ultrasonic transducers according to certain design specifications has received limited recognition. To illustrate the power of CAD for providing better designs, this paper departs from the more conventional approach (controlling bonding and matching layers) and outlines a design strategy employing appropriate broadband matching networks.” (Authors), 11 refs.Google Scholar
- 1975–471.Goll, J. H. and Auld, B. A., “Multilayer Impedance Matching Schemes for Broadbanding of Water Loaded Piezoelectric Transducers and High Q Electric Resonators,” IEEE Trans. Son. Ultrason., SU-22 (1), 52–53. “High efficiency, low ripple piezoelectric transduction into a water load has been achieved experimentally over a bandwidth of about 70% by using a two-layer acoustic impedance matching transformer. Similar performance is predicted for properly designed transducers in a frequency range of 1 to 40 MHz.” (Authors), 3 refs.Google Scholar
- 1977–472.Myrick, R. J. and Arthur, R. M., “Real-Time Digital Echocardiography Using Burst Analog Sampling,” IEEE Trans. Son. Ultrason., SU-24 (1), 19–22. “Analog domain samples, acquired at high speed during the period of the echo from an ultrasonic pulse were stored in a series of sample-and-hold circuits. Analog samples were read out slowly for analog-to-digital (A/D) conversion during the subsequent interval before the next ultrasonic pulse. Burst analog sampling circuitry was combined with a conventional 9-bit A/D converter and a minicomputer to form a digital echocardiograph. An effective sample rate of 7 MHz was obtained with an actual A/D rate of 70 KHz. Gain could be altered under processor control for automatic depth compensation. The A/D rate could be varied by the processor to make analysis context dependent. The system operated in real time at 100 ultrasonic pulses/s. It was tested in A-mode and time-motion studies of cardiac structures.” (Authors), 5 refs.Google Scholar
- 1977–473.Weinert, R. W., “Very High-Frequency Piezoelectric Transducers,” IEEE Trans. Son. Ultrason., SU-24 (1), 48–54. “A discussion of some general problems associated with high-frequency bulk-wave transducer-delay line systems is presented. Design curves concerning the radiation resistance of M-Zn0-M-delay line systems are given, where M represents the metal electrodes and is taken as Au, Ag, or Al for calculation purposes. Some data concerning a 0, π, 0, π beam steering mosaic transducer, which has application in high-frequency broad-band acoustooptic devices, is presented.” (Author), 13 refs.Google Scholar
- 1977–474.Milsom, R. F., Reilly, N. H. C. and Redwood, M., “Analysis of Generation and Detection of Surface and Bulk Acoustic Waves by Interdigital Transducers,” IEEE Trans. Son. Ultrason., SU-24 (3), 147–166. “A method of analysis which uses a combination of analytical and numerical techniques has been developed to obtain an accurate solution to the coupled electromagnetic and acoustic fields set up by an interdigital transducer on the surface of a piezoelectric substrate. Full account is taken of the coupling to bulk modes as well as surface modes, and the solution for the charge on the electrodes includes both electrostatic charge and piezoelectrically regenerated charge. Programs have been written for interdigital arrays with uniform aperture but varying electrode width and pitch and arbitrary electrical connections. The theory is also valid for arbitrary crystal orientations. Generation and detection may be analyzed separately with information being provided on the partition of power into the various acoustic modes and the external load impedance, and the bulk wave radiation patterns are also computed. The program may also be used to find the insertion loss of a p ir of transducers. Results are presented for the Bleustein-Gulyaev orientation of PZT-4 ceramic and the YZ and 41° rotated YX orientations of lithium niobate.” (Authors), 31 refs.Google Scholar
- 1978–475.Linzer, M., Shideler, R. S., and Parks, S. I., “Ultrafast Signal Averaging and Pulse Compression Techniques for Sensitivity Enhancement,” Proc. 1st Int. Symp. on Ultrason. Mat. Char., Gaithersburg (June, 1978). “A signal averager and pulse compression system has been developed for sensitivity enhancement in ultrasonic diagnosis. The averager is capable of real-time (unbuffered) averaging at 50 MHz rates. . . . The pulse compression circuit incorporates a surface acoustic wave (SAW) ‘chirp1 filter. Pulse compression ratios of 30 il and 8 il have been obtained in the case of 8 MHz and 3 MHz filter bandwidths, respectively.” (Authors)Google Scholar
- 1978–476.von Gutfeld, R. J., “MHz Acoustic Waves from Thermoelastic Expansion of Thin Film-Liquid Interfaces,” Proc. 1st Int. Symp. on Ultrason. Mat. Char., Gaithersburg (June, 1978). “We have extended the work on laser induced thermoelastic expansions obtained from acoustically clamped thin metal films in the MHz range. In the work . . . reported here, we study the elastic waves generated from a structure consisting of a clamped metal film in contact with a liquid. ... A 5 nsec pulsed edge laser was used as the excitation source together with piezoelectric receivers . . . Based on new results we show some simple structures which use high thermal expansion liquids, such as acetone, to obtain strain amplitudes in liquids considerably larger than any previously observed by us . . .” (Authors), 2 refs.Google Scholar
- 1978–477.Rocha, H. A. F., Griffen, P. M., and Thomas, C. E., “Opto-Acoustic and Acousto-Electric Wideband Transducers,” Proc. 1st Int. Symp. on Ultrason. Mat. Char., Gaithersburg (June, 1978). “Two major problems are considered: 1) generation of fast acoustic pulses; and 2) detection and amplification of the corresponding echoes without appreciable waveform degradation. The first problem is solved by the use of a short optical pulse which, when suitably absorbed, produces an acoustic stress-wave. The second problem required the design and construction of electrostatic transducers with a bandwidth compatible with that of the generated acoustic stress waves. . . . The combination laser transmitter/electrostatic receiver has many advantages over conventional piezoelectric elements. For instance: a) A simple lens can be used to change the size of the optical beam falling on the absorber. This is equivalent to having a transmitter with a continuously variable diameter. b) Small spot sizes can generate very wide acoustic beams. Beam widths (at 50 percent points) of 160 degrees have been measured in aluminum. c) Cylindrical lenses can be used to produce the equivalent of a transducer with a continuously variable shape. d) Electro-optic deflectors can produce one- and two-dimensional scanning arrays.” (Authors)Google Scholar
- 1978–478.Resch, M. T., Khuri-Yakub, B. T., Kino, G. S., and Shyne, J. C., “Stress Intensity Factor Measurement of Surface Cracks,” Proc. 1st Int. Symp. on Surface Cracks,” Proc. 1st Int. Symp. on Ultrason. Mat. Char., Gaithersburg (June, 1978). “It was shown by Budiansky and Rice that the maximum stress intensity factor of an internal crack can be determined by measurements of the acoustic wave scattering from a crack. We have carried out a simple theory to predict the reflection coefficient of a surface acoustic wave in terms of the stress intensity factor of a surface crack, and predicted from the acoustic measurement the breaking stress of the material.” (Authors)Google Scholar
- 1978–479.Varadan, V. K., and Varadan, V. V., “Characterization of Dynamic Shear Modulus in Inhomogeneous Media Using Ultrasonic Waves,” Proc. 1st Int. Symp. on Ultrason. Mat. Char., Gaithersburg (June, 1978). “We propose to examine this problem from a scattering theory approach. The model that we will study is a two-dimensional one, namely, a medium containing a random or periodic array of infinitely long cylinders of different material. Shear (SH-) waves are assumed to propagate normal to the axis of the cylinders. The wave undergoes multiple scattering between the cylinders and the effective wave number in the medium is complex. An ensemble average of the displacement field will be performed for a random distribution of the scatterers and expressions will be obtained for the average stress and the displacement field which are related by the average elastic modulus. The scattering properties of each scatterer will be characterized by the T-matrix which depends on the geometry and nature of the scatterer. Using this approach, we have already obtained the phase velocity and attenuation of SH-waves in a medium containing cylinders of elliptical cross section for a wide range of frequencies. Our approach for relating the average stress to strain using scattering theory bears some resemblance to the treatment given by Bedeaux and Mazur for studying the macroscopic dielectric tensor of an inhomogeneous medium.” (Authors)Google Scholar
- 1978–480.Lloyd, E. A. and Wadhwani, D. S., “Ultrasonic Spectroscopy and the Detection of Hydrothermal Degradation in Adhesive Bonds,” Proc. 1st Int. Symp. on Ultrason. Mat. Char., Gaithersburg (June 1978). “Analytical methods have been developed; determined largely by the geometry of the adhesives and adherent layers under investigation. The use recently of adherent aluminum alloy layers some 4 mm in thickness and supported film adhesives (BSL 312/5) giving adhesive layers some 0.3 mm thick has proved to be a particularly favorable geometry for study. . . . The second signal returned is reflected from the adhesive bond itself with a spectral window leading to 15 MHz, one, and in many instances, two reflectivity minima are recorded. The position of these minima are inversely related to the transit time in the adhesive layer itself and the depth of modulation is a measure of the two interfacial reflectivities between the adherent and adhesive layers. The sensitivity of the test can be significantly increased by examining the relationship between the third signal returned and the second signal cited. This third signal represents a double reflection from the adhesive layer plus a double transmission through the bond. . . . When an adhesively bonded joint is subject to a combination of high humidity and temperature both reversible and irreversible degradation, manifest as a reduction of strength, occurs. Within the reversible regime the bonds tend to fail cohesively. This regime, although not yet fully investigated is manifest by a reduction in modulation and a corresponding drop in the frequency at which the bond-line absorption minima occurs.” (Authors)Google Scholar
- 1978–481.Shankar, R., Mucciardi, N., and Lawrie, W. E., “Application of Adaptive Learning Networks to Ultrasonic Signal Processing; Detecting Cracks in Stainless Steel Pipe Welds,” Proc. 1st Int. Symp. on Ultrason. Mat. Char., Gaithersburg (June, 1978). “Unambiguous discrimination has been achieved between cracks and geometrical (benign) reflectors in sample welded sections on 304 Stainless Steel (SS) pipes using nonlinear signal processing of ultrasonic pulse echoes via the Adaptive Learning Network (ALN) methodology. . . . For the preliminary scan, the ALN classifier was synthesized from a small set of spectral parameters computed from the UT waveform. The parameters included the fractional spectral content in frequency bins descriptive of the low-(0 to 1 MHz), mid-(l to 2 MHz), and high-(2 to 4 MHz) frequency ranges, and higher order moments of the UT power spectrum. The synthesized ALN classifier “false dismissal” rate (the percentage of cracks falsely dismissed as geometrical reflectors) was zero percent, while the false alarm rate (the percentage of nondefects called cracks) was 33 percent. For the more detailed scan, the ALN classifier was synthesized from parameters related to spectral shifts in an ensemble of pulse-echo waveforms collected around the vicinity of a region tagged as suspicious during the preliminary scan. The waveform ensemble was obtained by angulating the transducer over ± 11°, in increments of 5.5°, around the nominal normal to the assumed crack plane. The ALN classifier reduced the false-alarm rate to zero and, therefore, discriminating unambiguously between cracks and benign geometrical reflectors.” (Authors)Google Scholar
- 1978–482.Goebbels, K. and Höller, P., “Quantitative Determination of Grain Size and Detection of Inhomogeneities in Steel by Ultrasonic Backscattering Methods,” Proc. 1st Int. Symp. on Ultrason. Mat. Char., Gaithersburg (June 1978). “Ultrasonic waves in steel are attenuated by absorption and scattering. Scattering from grains or phase boundaries can be measured and in backscattering experiments as a function of time of flight scattering signals are detected and evaluated. Two physical conditions determine grain scattering: 1. From the different regions Rayleigh, stochastic and diffuse scattering in practice only the first and the second one are of interest. 2. Scattering is only stimulated if there is a change in the wave-resistance at grain boundaries (because of the elastical anisotropy) or phase boundaries (because of change in density and/or velocity).... Several methods allow to evaluate the mean grain size of the material under test by backscattering experiments: a. Measurements with two frequencies under the condition, that the frequency dependence of the absorption coefficients is known. b. Measurements at two samples with one frequency under the condition, that alpha is the same in the two samples. c. One measurement with a frequency high enough, that multiple scattering is generated (without assumptions concerning alpha).” (Authors)Google Scholar
- 1978–483.Heyman, J. S., Cantrell, J. H., Jr., and Whitcomb, J. D., “A Phase Insensitive Transducer—Theory and Application,” Proc. 1st Int. Symp. on Ultrason. Mat. Char., Gaithersburg (June, 1978). “Materials characterization with ultrasonics is examined from the viewpoint of the receiving transducer. Signal artifacts are shown to exist for conventional phase sensitive piezoelectric transducers. The signal artifacts are always present when differing phases (and/or frequencies) are present on any phase sensitive receiver whose dimensions are greater than an acoustic wavelength. Attenuation measurements with this class of receivers under the above circumstances can lead to values of attenuation in error by orders of magnitude. These phase cancellation artifacts are eliminated with the use of an acousto-electric transducer (AET) since it is insensitive to phase variations across its face. Characteristics of the AET are contrasted with conventional transducers and are shown to be significantly superior where phase variations exist in the acoustic wave front.” (Authors)Google Scholar
- 1978–484.Klinman, R., Marsh, F. J., Stephenson, E. T., and Webster, G. R., “Ultrasonic Prediction of Grain Size, Strength and Toughness in Plain Carbon Steel,” Proc. 1st Int. Symp. on Ultrason. Mat. Char., Gaithersburg (June, 1978). “It is well known that the mean ferrite grain size and mechanical properties of steel are closely related. Metallographic measurement of grain size is both time-consuming and destructive to the product tested. The ultrasonic literature demonstrated that the contribution of scattering to ultrasonic attenuation can be used to determine the mean grain size. However, little work has been carried out to apply ultrasonically estimated grain size to directly predicting the mechanical properties of steel. Use of ultrasonic measurements for this purpose is potentially attractive, because they are rapid and nondestructive and could conceivably be applied to the on-line measurement of properties during primary processing. . . . Our data agree with published results relating grain size to ultrasonic attenuation. They also agree with accepted Hall-Petch relationships between: a) grain size and yield strength, and b) grain size and Charpy transition temperature. Multiple regression analysis of our data showed that the lower yield strength can be estimated to ± 3.5 ksi and transition temperature to ± 32 F at a 95 percent confidence level by the combined use of: a) the ultrasonically measured grain size in the optimum part of the Rayleigh region, and b) knowledge of the chemical composition. This work supports the potential for development of a nondestructive test for predicting yield strength, but much work remains before a production test can be implemented.” (Authors)Google Scholar
- 1968–485.Lee, R. E. and White, R. M., “Excitation of Surface Elastic Waves by Transient Surface Heating,” Appl. Phys. Lett. 12 (1), 12–14. “The generation of surface elastic waves by the transient surface heating of piezoelectric and nonpiezoelectric solids is described. A Q-switched ruby laser produces the surface heating; the frequencies of the resultant surface waves are Fourier components of the laser waveform. The use of a spatially periodic illumination is shown to increase the effectiveness of generation at a selected frequency. This method of generating surface waves appears suitable for microwave frequency operation as well as operation at high wave amplitudes at low frequencies.” (Authors), 10 refs.Google Scholar
- 1973–486.Bunkin, F. V. and Komissarov, V. M., “Optical Excitation of Sound Waves,” Sov. Phys. Acoust. 19 (3), 203–211. “When the powerful optical radiation emitted by present-day lasers interacts with a medium, sound waves can be excited in the latter. The physical mechanism of the excitation can be one of several. Below we discuss only those which are unrelated to nonlinear optical effects, i.e., for which nonlinear interaction between the radiation and matter is insignificant. We therefore exclude, for example, the sound generation mechanism due to induced Brillouin scattering. It is also important to note that even within the framework of the investigated mechanisms the amplitude of the excited sound can be very large. Nonlinear acoustical effects become significant in this case (in particular, shock waves can be generated).” (Authors), 36 refs.Google Scholar
- 1962–487.Papoulis, A., The Fourier Integral and Its Applications. McGraw-Hill, New York, 1962.Google Scholar
- 1978–488.Vary, A., “Use of an Ultrasonic-Acoustic Technique for Nondestructive Evaluation of Fiber Composite Strength,” NASA-TM-73813. “This report describes the ultrasonic-acoustic technique used to measure a “Stress Wave Factor.” In a previous study this factor was found effective in evaluating the interlaminar shear strength of fiber-reinforced composites. Details of the method used to measure the stress wave factor are described. In addition, frequency spectra of the stress waves are analyzed in order to clarify the nature of the wave phenomena involved. The stress wave factor can be measured with simple contact probes requiring only one-side access to the part. This is beneficial in nondestructive evaluations because the probes can run parallel to fiber directions and thus measure material properties in directions assumed by actual loads. Moreover, the technique can be applied where conventional through transmission techniques are impractical or where more quantitative data are required. The stress wave factor was measured for a series of graphite polymide composite panels and results obtained are compared with through transmission immersion ultrasonic tests.” (Author), 5 refs.Google Scholar
- 1978–489.Vary, A., “Correlations Among Ultrasonic Propagation Factors and Fracture Toughness Properties of Metallic Materials,” Mat. Eval., June, 1978, 55–64. “Empirical evidence was developed to show that a close relation exists among fracture toughness, yield strength, and ultrasonic attenuation properties of metallic materials. The evidence was obtained by ultrasonic probing of specimens of two maraging steels and a titanium alloy. It was concluded that nondestructive ultrasonic methods can be used to indirectly evaluate fracture-related material properties. The results suggest that these nondestructive ultrasonic measurements can also serve as an adjunct to destructive testing, measurement, and analysis of fracture properties.” (Author), 19 refs.Google Scholar
- 1968–490.Papadakis, E. P., “Ultrasonic Attenuation Caused by Scattering in Poly-crystalline Media,” Chap. 15 of Physical Acoustics, Vol. IV, Part B, W. P. Mason, ed., Academic Press (New York), 269–329. 85 refs.Google Scholar
- 1969–491.Youshaw, R. A., Criscuolo, E. L., and Dyer, C. H., “The Magnetic Tape Recording of Ultrasonic Test Information,” Mat. Eval., February, 1969, 34–36 and 41. “This paper describes a method of recording primary ultrasonic test information. A videotape recorder has been converted into a wide band instrumentation recorder. The “A” scan from the ultrasonic tester is directly recorded, together with the operator’s voice giving the location, transducer position and interpretation of test data. An oscilloscope is used for the playback. The circuitry necessary to couple the output of the ultrasonic tester to the tape recorder is described.” (Author), 6 refs.Google Scholar
- 1978–492.Kline, R. A., Green, R. E., Jr., and Palmer, C. H., “A Comparison of Optically and Piezoelectrically Sensed Acoustic Emission Signals,” J. Acoust. Soc. Am., 64 (6), 1633–1639. “The ususal sensor for acoustic emission is the piezoelectric transducer. Although this transducer is readily available, reasonably inexpensive, and very sensitive to ultrasonic transients, it has several serious drawbacks as a transducer: It distorts the signals being measured, it exhibits resonances, it has limited bandwidth, it responds differently to surface acoustic waves and bulk waves (because of its large sensitive area), and its calibration is a matter of considerable uncertainty. Essentially, it is a qualitative transducer. Furthermore, it cannot measure local effects within a millimeter of an emission source, where the mechanisms causing the ultrasonic transient are presumably most clearly distinguishable. Optical transducers, on the other hand, have the great advantage of providing accurate, quantitative, highly localized information; they do not disturb the waves being measured and are not limited by frequency response.” (Authors), 18 refs.Google Scholar
- 1970–493.Elliott, B. J., “System for Precise Observations of Repetitive Picosecond Pulse Waveforms,” IEEE Trans. Instrum. Msmt., November, 1970, 391–395. “Conventional sampling techniques yield minimum risetime in the oscillography of repetitive electrical waveforms. However, system timing uncertainties introduce drift and jitter errors, which are typically comparable in magnitude to the cathode-ray-oscilloscope risetime. By using two sampling oscilloscopes in cascade it is possible to reduce the drift by a factor of 10–3, down to a level of 10–14 seconds (during an averaging and recording time interval of 2 minutes). Successive sampling also allows accurate jitter filtering. With the aid of a tunnel-diode step generator the total system has a 10–90 percent risetime of 25 × 10–12 second, a step response that is closely integral Gaussian, a time-measurement uncertainty of about 10–13 second, and amplitude accuracy of 0.2 percent. Absolute time calibration is possible with a 3 × 10–14-second resetting capability. Applications include the measurement of the impulse-response functions of coaxial two-port networks in the 10–11-second range. Finally, it is shown that amplitude averaging at a sampled waveform with time jitter causes convolution error and loss of resolution.” (Author), 5 refs.Google Scholar
- 1973–494.Lees, S., Gerhard, F. B., Barber, F. E., and Cheney, S. P., “DONAR: A Computer Processing System to Extend Ultrasonic Pulse-Echo Testing,” Ultrasonics, July, 165–173. “A dedicated general purpose digital computer has been built on the principle of a sampled-data system to run an ultrasonic subsystem under programmed control. A most significant application is the ability to extract a signal from an interfering background. As illustrated in the paper, a 1 mm diameter transducer was used to measure the diameter of a 2.5 mm OD plastics tube with 0.4 mm wall thickness. Echoes from all four surfaces were displayed and the measurements indicated an uncertainty of less than 0.1 mm.” (Authors), 5 refs.Google Scholar
- 1976–495.Fay, B., Brendel, K., and Ludwig, G., “Studies of Inhomogeneous Substances by Ultrasonic Back-Scattering.”Ultrasound in Med. and Biol. 2 (3), 195–198. “A method is outlined by which ultrasonic back-scattering measurements may reveal information concerning both the scattering and absorption properties of inhomogeneous substances. After a description of the principle of the measuring method, experimental studies of a sample consisting of four layers with different scattering properties are discussed. To carry out measurements on substances, the acoustic properties of which are similar to those of biological tissues, inhomogeneous gelatine gels are investigated. The gels are produced using appropriate ethanol-glycerine mixtures. The inhomogeneities were introduced by adding tiny plastic spheres to the gel. It is shown, that the ultrasonic back-scattering method allows separation of the attenuation into scattering and absorption as functions of the location. In this way recognition of the inhomogeneities is possible. This fact should be helpful in the field of medical diagnostics.” (Authors), 9 refs.Google Scholar
- 1973–496.Fay, B., “Theoretische Betrachtungen zur Ultraschal 1-rűckstreuung,” Acustica 28, 354–357. “Theoretical Considerations of Ultrasound Back-Scatter” “Nondestructive structure testing with ultrasound using the impulse-echo method on materials with localized structure only yields the attenuation constant averaged over the sound path. Using theoretical considerations it will be shown that by the method of ultrasonic back-scatter one can calculate the change of back-scatter and absorption coefficient in materials.” (Author), 7 refs.Google Scholar
- 1978–497.Sigrist, M. W. and Kneubűhl, F. K., “Laser-Generated Stress Waves in Liquids,” J. Acoust. Soc. Am. 64 (6), 1652–1663. “The generation of laser-induced stress waves in liquids by the vaporization process and the thermoelastic effect was studied experimentally. A high-speed camera and special high-sensitivity stress transducers with a response time of a few nanoseconds have been used for these investigations. The experimental results obtained for water, n-heptane, and carbon tetrachloride are discussed. For the first time, the individual contribution of vaporization and the thermoelastic effect on stress generation are separated. In addition, tunable high-frequency acoustic waves, with frequencies up to 60 MHz, have been generated in water by the impact of a laser pulse exhibiting longitudinal mode beating. Since existing theories on the thermoelastic generation of acoustic waves do not yield satisfactory agreement with our experimental data, a new spherical model is proposed, where the transient heating caused by the laser impact, is represented by the three-dimensional heat pole. This solution of the equation of heat conduction corresponds to a Gaussian distribution of the excessive temperature in space, and thus to the TEM
_{00}mode of the incident laser beam. An analytical solution of the thermo-elastic presure wave is derived for this case of temperature distribution. Its good agreement and the experiment is discussed for various liquids and for two different laser characteristics.” (Authors), 64 refs.Google Scholar - 1973–498+.Canella, G., “Resonances and Effects of Couplant Layers in Ultrasonic Contact Testing,” Mat. Eval., 61–66 (April). “A theoretical and experimental examination has been carried out on the variation of echo amplitude as a function of the thickness of the liquid couplant layer in direct-contact ultrasonic testing, using compression waves. Four liquids were used and compared, namely water, glycerine, lubricating oil, and oil for penetrant liquids. The theoretical resonances were confirmed by experimental measurements. Amplitude differences of up to 20 dB were measured for variations in liquid thickness of 0.1 mm. The echo amplitude was also measured as a function of thickness of the protective layers of rubber and it was found that the maximum efficiency of a probe is attained at a fixed thickness of these layers.” (Author), 5 refs.Google Scholar
- 1978–499+.Childers, D. G. (editor), Modern Spectrum Analysis. IEEE Press, New York. “Power spectrum estimation has progressed through several stages since the turn of the century. Perhaps the first estimator to be used extensively was the periodogram which, although it is known to be a poor estimator because the variance of the estimate exceeds its mean value, is still used today. Twenty years ago in 1958 Blackman and Tukey published their autocorrelative method for power spectrum estimation, the steps of which include estimating the autocorrelation function from the observed data, windowing the autocorrelation estimate in an appropriate manner and then Fourier transforming the windowed autocorrelation function to finally obtain the estimated power spectrum. With the advent of the fast Fourier transform (FFT) algorithm in 1965, the direct method for power spectrum estimation became popular. This approach generally uses the magnitude squared of the transform of the windowed data record as the power spectrum estimate. More recently, the maximum entropy method (MEM) for spectral estimation has attracted the attention of scientists and engineers. This procedure is equivalent to the linear predictive and autoregressive methods and is being applied to a wide range of data because of its potential to achieve increased spectral resolution. Another recent technique is the maximum likelihood method (MLM) which has been used for high resolution frequency wavenumber spectral estimation. The MEM and MLM are related as we shall discuss later and as one of the reprints (Burg, 1972) shows. This collection of papers concentrates on the MEM and MLM but we do provide two background papers as well as a brief tutorial review of the other major spectral estimation procedures.” (Editor), numerous references.Google Scholar
- 1975–500+.Ramirez, R. W., The FFT: Fundamentals and Concepts,” Tektronix, Inc., Beaverton, OR, Part 070–1754–00.Google Scholar
- 1973–501+.Auld, B. A., Acoustic Fields and Waves in Solids, Wiley, New York.Google Scholar
- 1979–502.Rose, J. H. and Krumhansl, J. A., “A Technique for Determining Flaw Characteristics from Ultrasonic Scattering Amplitudes,” Proc. ARPA/AFML Rev. of Prog. in Quant. NDE, AFML-TR-78–205, 368–372. “We report an approximate technique for determining the characteristics of flaws in elastic media from a knowledge of their ultrasonic scattering amplitudes. The technique is rigorously valid in the weak scattering limit. Good results have been obtained for strongly scattering flaws. In particular, we tested the technique for a 2–1 oblate spheroidal void in Ti, and for various strongly scattering spherical defects. For these tests the technique yields good results for the volume of the flaws. In the case of the oblate spheroid, satisfactory results were obtained for the calculated ratio of major to minor axis, indicating that the technique is sensitive to the shape of the flaw.” (Authors), 10 refs.Google Scholar
- 1979–503.Richardson, J. M.,”Direct and Inverse Problems Pertaining to the Scattering of Elastic Waves in the Rayleigh (Long Wavelength) Regime,” Proc. ARPA/AFML Rev. of Prog. in Quant. NDE, AFML-TR-78–205, 332–340. “It is well known that in the scattering of elastic waves from localized inhomogeneities the scattering amplitude A is proportional to the square of the frequency ω in the Rayleigh (long wavelength) regime, i.e., A = A
_{2}ω^{2}+ ... This talk deals with the problem of (1) extracting A_{2}from experimental scattering data, (2) calculating A_{2}for an assumed scatterer and (3) deducing the properties of the scatterer from a set of values of A_{2}measured for various transducer configurations. A review of experimental and theoretical results for A_{2}will be presented for the case of spheroidal voids and the remaining discrepancies between the two kinds of results will be discussed. The inverse problem (i.e., deducing the scatterer properties from the scattering measurements) will be discussed in detail. The probabilistic inverse problem, which provides the appropriate framework for the interpretation of real data, will be covered at greater length. In the case in which it is assumed that the scatterer is an ellipsoid void, whose size, shape and orientation are unknown a priori, a number of computational results involving best estimates and associated measures of significance will be given. Analogous results will be derived for parameters related to fracture mechanics.” (Author), 12 refs.Google Scholar - 1979–504.Achenbach, J. D., Adler, L., Lewis, D. K. and McMaken, H., “Diffraction of Ultrasonic Waves by Penny-Shaped Cracks in Metals: Theory and Experiment” (accepted for publication in J. Acoust. Soc. of Am., 1979. “In this paper an analytical solution to the diffraction of elastic waves by penny-shaped cracks in metals is compared with experimental observations. The analysis, which is based on elastodynamic ray theory, is valid for the region of ka > 1. A digitized spectrum analysis system is described which measures the frequency components of the waves diffracted from a 2500 y radius crack in diffusion bonded titanium. The amplitude spectra show good agreement between experiment and theory. The theoretically predicted periodicity of the diffracted spectra provides a simple formula for the inverse problem. Application of this formula to the experimental measurements determines the crack size with excellent accuracy.” (Authors) 16 refs.Google Scholar
- 1979–505.Adler, L. and Achenbach, J. D., “Elastic Wave Diffraction from Elliptical Cracks: Theory and Experiment” (will be published in J. of Nondestr. Eval.).Google Scholar
- 1980–506.Crane, R. L. and Nayfeh, A., “Fundamental Considerations in the Nondestructive Measurement of Adhesive Bond Properties,” Proc. of ASNT Spring Conf., Philadelphia (March 1980). “Recently there has been a great deal of research with a goal of the predicting of the mechanical response of adhesively bonded joints. Several techniques have been developed that purportedly correlate an ultrasonic parameter such as wave speed, attenuation, or an acoustic spectral feature with lap shear strength. These techniques are fundamentally based on the empirical observation that there is a weak correlation between stiffness and ultimate tensile strength for many polymeric materials. If the stress distribution in the adhesive joint is taken into account, then it can be shown that such correlations depend critically on two assumptions that do not usually occur in service: (1) the uniformity of the adhesive and (2) the absence of defects. A fracture mechanics/acoustic model is presented which shows what measurements need to be made before predictions of the mechanical response of the adhesive joint can be made. Supporting data will also be presented.” (Authors)Google Scholar
- 1978–232+.Nabel, E. and Mundry, E., “Evaluation of Echoes in Ultrasonic Testing by Deconvolution,” Mat. Eval., 59–61, 77, Jan., 1978. “This paper is based on what has turned out to be a good tool for ultrasonic echo analysis, namely, linear system theory, and will report some effects of fundamental importance for ultrasonic spectroscopy and deconvolution. In many cases the importance of these effects is not recognized, although they are responsible for most of the differences between experimental results and theory. The paper deals with the improvements in the analysis of echo indications by the calculation of the impulse response of a reflector (deconvolution of ultrasonic echoes). The importance of phase information is emphasized, and the influence of the low frequencies (i.e., the low diffraction orders) on the experimental results is shown. As an example, the result of a simulated convolution will be demonstrated with respect to the theory of replica pulses published by Freedman.” (Author) 11 refs.Google Scholar
- 1977–233.Tamburelli, C., “Use of Ultrasound in Assessing the Susceptibility of Steel to Lamellar Tearing,” NDT International, 3–8, Feb., 1977. “Increasingly, developments in welded constructions means that steel plate with high resistance to lamellar tearing has to be used. An experimental programme has been carried out on 17 C/Mn Fe52D steels, to indicate what features of longitudinal wave transmission ultrasonics may be used in assessing susceptibility to lamellar tearing. A combination of two kinds of evaluation proved promising: the contribution of matrix toughness, measured from the anisotropy of ultrasonic velocity; and the contribution of the amount of inclusions, assessed by ultrasonic attenuation measurements and inclusion counting by ultrasonic reflection. No useful results have been obtained from ultrasonic spectroscopy.” (Author) 7 refs.Google Scholar
- 1978–234+.Budiansky, B. and Rice, J. R., “On the Estimation of a Crack Fracture Parameter by Long-Wavelength Scattering,” J. App. Mech. 45 (2). “Attention is focussed herein on the possibility of estimating the fracture-mechanics parameter k
_{I}= (K_{I})max/σ associated with a flat crack of initially unknown dimensions and orientation by using long-wavelength NDE measurements. Here K_{I}is the mode I stress-intensity factor associated with tension σ normal to the plane of the crack, and “max” denotes the largest value along the crack perimeter. The estimates will be made on the basis of the long wavelength studies by Gubernatis, et al. [1]3, and certain properties of elliptic cracks that are nearly shape invariant.” (Author) 2 refs.Google Scholar - 1975–235+.Canella, G., “The Ultrasonic Field in Water and Steel,” NDT (London), 38–42 (Feb., 1975). “The investigations of the ultrasonic field of transducers used in ndt, had two objects. The first was to compare directly propagation in steel and water. The second was to study the contribution of the beam spread to the attenuation of the echo. The beam spread is considered as a function of the area of the reflector and its distance from the transducer.” (Author) 9 refs.Google Scholar
- 1977–236+.Baboux, J. C., Lakestani, F., Fleischmann, P., and Perdrix, M., “Calibration of Ultrasonic Transmitters,” NDT International.1977, 135–138 (June, 1977). “A simple experimental method is described which enables the absolute measurement of the acoustic pressure transmitted by a transducer. After a theoretical study of the method used, some experimental results on industrial transducers are given.” (Author) 2 refs.Google Scholar
- 1974–237+.Highmore, P. J., “Nondestructive Testing of Bonded Joints—The Depth Location of Non-Bonds in Multi-Layered Media,” NDT (London), 327–330, Dec, 1974. “In some types of multi-layered structure it is important to detect not only the presence of non-bonds but also to determine their depth locations. This paper describes a simple ndt method, designed especially to meet this requirement, based on the well-known ultrasonic resonance technique.” (Author) 1 ref.Google Scholar
- 1977–238+.Thompson, L. A., “Method of Response Equalization for a Piezoelectric Transducer,” J. Acoust. Soc. Am. 62(6). “A method of using the skirt of a low-pass filter to flatten the projecting response of a piezoelectric transducer is described. An example is given in which the 30 dB response variation of an F-27 standard transducer over the 20–80-kHz frequency range is reduced to 9 dB.” (Author) 1 ref.Google Scholar
- 1972–239+.Myers, G. H., Thumin, A., Feldman, S., deSantis, G. and Lupo, F. J., “A Miniature Pulser-Preamplifier for Ultrasonic Transducers,” Ultrasonics, 87–89 (March, 1972). “In order to avoid difficulties experienced with conventional ultrasonic systems using several feet of shielded cable to connect transducer and electronics, a miniature pulser-preamplifier was developed to fit the transducer holder. Its characteristics proved superior to most devices in common use.” (Author) 3 refs.Google Scholar
- 1977–240+.Hill, J. J., “A Simple Digital Pulse-Shaping Circuit,” Proc. IEEE., 1517 (1977) “A method of generating pulses of prescribed shape is described where binary-coded samples of the pulse are stored in a READ-ONLY memory. The proposed circuit is used to generate pulses having a Gaussian shape.” (Author) 2 refs.Google Scholar
- 1976–241.Cousins, R. R., “The Mathematical Theory for Ultrasonic Spectroscopy,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “A viscoelastic model is proposed to describe the loss of signal of an ultrasonic pulse due to both viscoelastic dissipation and scattering from defects. The material specimen is divided into a number of theoretical layers normal to the direction of travel of pulse, and an analysis of the frequency spectrum of the reflected pulse enables the properties of successive layers to be determined. In the case of laminated material the amplitude of the spectrum is sufficient to determine the depth of delaminated regions, and an experimental example is given.” (Author)Google Scholar
- 1976–242.Adler, L., “Scattering of Broad-Band Ultrasound from Geometrical Shapes Embedded in Metal,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “In order to develop realistic models for flaw characterization in NDE scattering of broadband ultrasonic pulses from various shaped cavities embedded in diffusion-bonded titanium was measured. The frequency and angular distribution of the scattered energy were analyzed and compared with two existing theories: (1) Keller’s geometrical theory of diffraction for the region ka ≧ 1, and (2) Bom’s approximation for the region ka ≦ 1.” (Author)Google Scholar
- 1976–243.Haines, N. F., “Deconvolution in Ultrasonic Spectroscopy,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “Ultrasonic spectroscopy techniques have been used in CEGB Nuclear reactors since 1974 to make measurements of corrosion layers on inaccessible steel surfaces. As from 1977 two of the boards regions will have their own spectroscopy systems with personnel trained to make these measurements on an operational basis. Research work at Berkeley Nuclear Laboratories is continuing into possible other areas of application. During the past 18 months theoretical work and more recently experimental work has demonstrated where spectroscopy techniques may be of use in understanding the reflection of pulses from real defects. The theoretical model developed can predict the reflected waveform and hence peak amplitude as a function of size, shape, orientation and surface roughness of a reflector. The underlying theme of the talk will be the relationship between the time domain and frequency domain. In some cases one domain may give greater physical insight into the system being considered than the other. In particular the reflection from surfaces are perhaps better understood in the time domain and hence the mathematical techniques of convolution and deconvolution become important.” (Author)Google Scholar
- 1976–244.Markham, M. F., “Polymeric and Composite Materials,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “An ultrasonic pulse transmission technique using a spectrum analyzer is described for studying secondary relaxation in polymers. Application to epoxide resins show that the technique yields the dynamic mechanical properties over a wide ultrasonic frequency band. A
*y*relaxation is located, and its behaviour under different cure conditions is investigated. A long term aging effect is also noticed, the study of which could lead to useful information regarding the molecular processes involved at various stages of cure.” (Author)Google Scholar - 1976–245.Lloyd, E. A., “Predictive Modeling of Ultrasonic Responses,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “In testing of structures fabricated from welded plate sections it is required to distinguish between signals returned from a weld bead of uncertain geometry and an equally variable defect echo. In order to understand better the factors governing the visibility of defects in this situation, a computer based modelling technique has been developed with which it is possible to vary the skip distance, probe angle, aperture and frequency response of a synthetic transducer. Whereas in the time-domain, the visibility of a defect will depend largely on the relative size and position of the defect response to the signal generated by the associated weld bead, no such obvious restriction need apply when the dual signal is examined in the frequency domain. There, the choice exists for examining the relative contributions of the defect and weld-bead over the whole or any part of the spectral “window” available for testing. It is for this reason that facilities have been built into the model so that both time-domain and frequency domain representations of a weld-bead associated defect signal can be synthesized. Results will be discussed. As a further test of the validity of the model, a short pulse shear wave transducer was used to interrogate slots of various depths milled over a flat plate. The features predicted are readily discernible.” (Author)Google Scholar
- 1976–246.Quentin, G., “Progress Towards an Ultrasonic Characterization of Rough Surfaces,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “New non-contact methods are described which lead to quite precise estimates of the r.m.s. roughness k of randomly rough surfaces as well as to a separation of periodic surface defects from random roughness. For k < 25 μm accuracy is of the order of ± lμm while for very rough surfaces with h > 50μm accuracy is ± 3μm. Some process has also been made in the measurement of the autocorrelation length.” (Author)Google Scholar
- 1976–247.Nabel, E., “The Importance of Phase for Ultrasonic Spectroscopy and Deconvolution,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “Much work has been done during recent years in the field of ultrasonic spectroscopy. Due to the fact that in most cases only swept frequency receivers were used for spectrum analysis which do not yield any phase information, phase spectrum was often regarded as being of no value. During the research work described in this paper spectrum analysis by means of a swept frequency receiver was replaced by calculating the complex spectrum that means amplitude and phase spectrum with a minicomputer. It became evident that the phase spectrum cannot be regarded separately from the amplitude spectrum. Amplitude and phase spectrum must be considered to be one unique set of data. Only that allows correct deconvolution, and makes it possible to calculate the impulse response of a reflector by inverse Fourier transform. The paper will describe some model experiments in an immersion tank and on a steel specimen, and that it is possible to describe the used reflectors easily by using a deconvolution technique and calculating the impulse response. The effects caused by neglecting phase information will be demonstrated with simulated and natural data.” (Author)Google Scholar
- 1976–248.Lepper, R. D., Decker, D., Trier, H. G., and Reuter, R., “Attempts to Characterize Tissues Using Spectroscopy,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “The paper deals mainly with the practical problems of implementing ultrasonic spectroscopy in the field of tissue differentiation. Firstly, the limitations of the authors1 experimental set-up of 1970 – 74 are discussed. A new set-up now gives considerable improvements, notably on-line digitization and less RF noise. Results are given of in-vitro experiments which reveal the difficulties of using the transfer function of tissue as well as experimental difficulties with highly damped transducers. A calibration method is proposed to overcome these difficulties.” (Author)Google Scholar
- 1976–249.Gore, J. C., and Leeman, S., “Cardiac Tissue Characterization by Ultrasonic Spectroscopy,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “An analysis of ultrasound scattering from tissues shows that the spectral content of the backscattered sound contains useful information about tissue density fluctuations. Such an analysis can be used to characterize tissues but it is shown that the information is limited by the nature of the interrogating sound pulse. When the echoes from heart wall are analyzed it is demonstrated that their spectra reveal information about the contractile state of the cardiac muscle. The extension of this method to the recognition of myocardial disease is presently being attempted and the utility of such information is discussed.” (Author)Google Scholar
- 1976–250.Nicholas, D. and Hill, C. R., “A Spectral Evaluation of Ultrasonic Backscattering from Human Tissues,” Seminar on Ultrasonic Spectroscopy, City University (London), 27 October 1976. “A number of human soft tissues exhibit structural features, and corresponding patterns of acoustic impedance variation, with characteristic spacings of the order of a millimeter. Bulk scattering from such tissues in the megahertz frequency region is thus diffractive in nature, exhibiting marked orientation dependence and a complex dependence on frequency. A series of investigations that have been carried out on these phenomena will be reported and their potential interest for in vivo tissue characterization will be discussed.” (Author)Google Scholar
- 1969–251+.Truell, R., Elbaum, C., and Chick, B. B., Ultrasonic Methods in Solid State Physics, Academic Press, New York (1969), 464 pp, 335 refs. This book contains chapters dealing with (1) propagation of stress waves in solids, (2) measurement of attenuation and velocity by pulse methods and (3) causes of losses and associated velocity changes. A section is included on the “specific application of the spectrum analyzer: factors affecting the spectrum.” The appendices contain diagrams of automated velocity and attenuation measurement systems.Google Scholar
- 1978–252.Davis, M. C., “Coal Slurry Diagnostics by Ultrasound Transmission,” J. Acoust. Soc. Am. 64 (2), 406–410. “Several application of ultrasonic detectors are suggested for monitoring coal water slurries in coal conversion processes. These include mass flow, particle size, and temperature. Modeling of transmission losses include viscous and thermal transport processes as well as multiscattering effects. Simple monitoring of sound attenuation versus frequency yields a unique dependence from which the value of characteristic parameters may be deduced, all from a single transmitter-receiver pair.” (Author) 8 refs.Google Scholar
- 1978–253.Ting, C. S. and Sachse, W., “Measurement of Ultrasonic Dispersion by Phase Comparison of Continuous Harmonic Waves,” J. Acoust. Soc. Am. 64 (2), 852–857. “The method of phase comparison of continuous waves is applied to determine the dispersion relation, phase, and group velocities as a function of dispersive materials. A combination of the variable frequency method and the variable path-length method is found necessary to eliminate any uncertainty in the dispersion relation determination. Experiments are performed on specimens of various thickness. A constraint equation can be derived since the dispersion relation is unique and independent of the specimen thickness. This equation provides a procedure for determining the absolute number of wavelengths in the specimen. Measurements in unidirectional, fiber-reinforced boron-epoxy specimens show good agreement with results reported previously.” (Author) 14 refs.Google Scholar
- 1978–254.Bray, D. E., Egle, D. M. and Reiter, L., “Rayleigh Wave Dispersion in the Cold-Worked Layer of Used Railroad Rail,” J. Acoust. Soc. Am. 64 (2), 845–851. “The first shear mode (Sezawa mode) and the fundamental Rayleigh mode have been identified as they propagated through the work-hardened layer on the top surface of used, steel railroad rail. Longitudinal wave velocities and densities are very nearly equal for the work-hardened layer and the subadjacent layer. The ratio of shear wave velocity in the upper layer to that in the subadjacent layer is near to 0.95. Experimental data obtained at several frequencies (0.5–2.0 MHz) showed good agreement with expected velocities for a layer thickness ranging from 3 to 5 mm.” (Author) 13 refs.Google Scholar
- 1970–255.Meyer, H. J., “Inspection of Grey Iron Castings by Ultrasonic Attenuation,” Non-Destruc. Test. (London), 99–104, April 1970. “Ultrasonic pulses of definite frequency and wavelength undergo a varying degree of scatter depending upon the size and quantity of graphite flakes in grey cast iron. The amount of sound energy left after a sound beam has passed a given cross-section provides, therefore, a measure of the structure and content of the graphite and consequently, the physical strength of the cross-section.” (Author) 10 refs.Google Scholar
- 1973–256+.Chang, F. H., Couchman, J. C. and Yee, B. G. W., “Transmission Frequency Spectra of Ultrasonic Waves through Multi-Layer Media,” Proc. 1973 IEEE Ultrasonic Symp. “The frequency spectrum of ultrasonic plane waves transmitted through a multi-layered laminate structure at normal incidence was analyzed to study the amplitude distribution of the frequency components. In supporting the theoretical calculations, the wave equation was solved to evaluate the displacement field with the appropriate boundary conditions in a six-region laminate. Cavity resonation of the plane waves in the layers produced peaks in the transmission frequency spectrum. Experiments were conducted using a pair of broad-band acoustical transducers transmitting a pulsed ultrasound centered at 5 MHz through multi-layer adhesive-bonded aluminum plates with different plate thicknesses. Resonant peaks in the experimental frequency spectra were compared with those theoretically calculated for regions of good bond and regions of disbond. Applications of this technique to nondestructive testing of bonded structures are described.” (Authors) 9 refs.Google Scholar
- 1978–257+.Hill, J. J., “Digital Generation of a Nonlinear Time-Base,” IEEE Trans. Instrum. Msmt., IM-27 (3), 298–300. “A Method of generating nonlinear time-bases is described. The approximation may be either step or piecewise linear and involves using a READ-ONLY memory as a look-up table to store digitally the shape of the required function. The case of a logarithmic time-base is considered in detail.” (Author) 4 refs.”Google Scholar
- 1978–258+.Khuri-Yakub, B. T. and Kino, G. S., “A New Technique for Excitation of Surface and Shear Acoustic Waves on Nonpiezoelectric Materials,” Appl. Phys. Lett., 32 (9), 513–514 (May 1978). “An interdigital transducer deposited on a piezoelectric substrate has been used to excite SAW on nonpiezoelectric materials by using a fluid couplant« The piezoelectric substrate is held at an angle to the nonpiezoelectric material so as to match the tangential k vectors of the surface waves. Experiments have been carried out with a LiNbO
_{3}piezoelectric substrate and a ceramic such as SiC or Si_{3}N_{4}with a fluid couplant. At a center frequency of 100 MHz, the estimated conversion efficiency of the surface wave from the piezoelectric to the nonpiezoelectric material is -3.5 dB. The results compare favorably with a normal mode coupling theory we have developed which predicts-2.7 dB efficiency.” (Authors) 8 refs.CrossRefGoogle Scholar - 1976–259+.Lakin, K. M. and Fedotowsky, A., “Characterization of NDE Transducers and Scattering Surfaces Using Phase and Amplitude Measurements of Ultrasonic Field Patterns,” IEEE Trans. Son. Ultrason., SU-23 (5), 317–322. “The characterization of transducers for quantitative NDE applications requires that the radiation pattern, conversion efficiency, and bandwidth be accurately determined. These quantities may, in principle, be determined if the transducer’s construction and constituent parts are independently known. However, most often the internal details of the transducer are unknown and subject to statistical variations and aging. A measurement technique and system for characterizing transducers based upon external measurements is described, which does not rely upon knowledge of the transducer’s construction.” (Author) 11 refs.Google Scholar
- 1978–260+.Fraser, J., Khuri-Yakub, B. T. and Kino, G. S., “The Design of Efficient Broadband Wedge Transducers,” Appl. Phys. Lett. 32 (11), 698–700 (June 1978). A simple coupled-mode theory has been developed for acoustic-surface-wave wedge transducers. Surface-wave transducers have been fabricated to operate on aluminum using water as the wedge material. The measured efficiency was 68% at 2.75 MHz, the theoretical value being 81%. Transducers have also been fabricated to operate on glass with a rubbery solid, RTV 615, as the wedge material. The experimental and theoretical efficiencies of this transducers at 3.2 MHz were 35 and 50%, respectively. The surface-wave leakage coefficient of RTV 615 on glass has been measured and found to be in excellent agreement with theory.” (Author) 5 refs.Google Scholar
- 1966–261.vander Pauw, L. J., “The Planar Transducers — A New Type of Transducer for Exciting Longitudinal Acoustic Waves,” Appl. Phys. Lett. 9 (3), 129–131 (August 1966). “We have constructed a new type of transducer for exciting longitudinal acoustic waves. It has only one interface, for which reason we shall call it a “planar” transducer. The planar transducer has comb-shaped electrodes which can be applied with a standard photo-mask technique. The frequency characteristics of the planar transducer turns out to be favorable compared with the frequency characteristic of the conventional transducer. We shall first mention the essential characteristics of the conventional transducer and then compare these with the characteristics of the planar transducer.” (Author). It is shown that the planar transducer has a wide-band frequency response, although the overall response seems to be about 10 dB lower than that of a plate transducer. 2 refs.Google Scholar
- 1978–262+.Rhyne, T. L., “An Improved Interpretation of Mason’s Model for Piezoelectric Plate Transducers,” IEEE Trans. Son. Ultrason. SU-25 (2), 98–103 (March 1978). “A new interpretation of Mason’s model for a piezoelectric plate transducer is presented. The network model emphasizes a series connection for the two acoustic loads while utilizing lumped impedance elements expressed as functions of the delay operator Z = exp sT. An exact analysis of the plate dynamics permits a simplified resistive model for conditions of light asymmetry in acoustic loading. A simplified resistive structure provides transmission (reception) loss near the half-wave resonance. Air backed front loading is modeled. Finally, RLC lumped component models are provided for evaluation of transducers as lumped element filters.” (Author) 18 refs.Google Scholar
- 1973–263+.Wright, H., “Impulse-Response Function Corresponding to Reflection from a Region of Continuous Impedance Change,” J. Acoust. Soc. Am. 53 (5), 1356–1359 (1973). “Acoustic reflection from a region of continuously varying specific acoustic impedance is characterized, in the linear circuit sense, by a unit reflection impulse-response function R(t). It is shown that in the absence of attenuation and for modest impedance excursions, the impulse-response function corresponding to reflection from a region which has continuously variable impedance along the incident axis is given by R(2t) ≈ (dz/dt)/4z, where z(t) is the impedance profile and t is acoustic travel time.” (Author).CrossRefGoogle Scholar
- 1973–264+.Sigelmann, R. A. and Reid, J. M., “Analysis and Measurement of Ultrasound Backscattering from an Ensemble of Scatterers Excited by Sine-Wave Bursts,” J. Acoust. Soc. Am. 53 (5), 1351–1355 (1973). “This paper develops a practical approximation for the backscattering of periodic bursts of sine waves by a volume of randomly distributed scatterers. The approximation is applied to the measurement of a ‘volumetric backscattering cross section,’ using a substitution method in which the rms value of the gated backscattered signal is compared with the rms value of a wave reflected from a target of known coefficient of reflection. It is shown that the signal backscattered from the ensemble depends on the attenuation of the wave in the volume and upon the burst and gate lengths. An equation to obtain the volumetric backscattering cross section from experimental data is derived.” (Author) 6 refs.CrossRefGoogle Scholar
- 1977–265+.Rhyne, T. L., “Radiation Coupling of a Disk to a Plane and Back or a Disk to Disk: An exact Solution,” J. Acoust. Soc. Am. 61 (2), 318–324 (February 1977). “The radiation coupling or coupling by propagating waves is solved for a disk in an infinite baffle to a plane and back or equivalently a disk to a disk both in infinite baffles. The radiation coupling is defined as a linear filter operating between lumped mechanical components which may be incorporated into transducer models. The impulse response of the radiation-coupling filter and the Fourier transfer function for the radiation-coupling filter are solved in closed form. The radiation-coupling gain (loss) is applicable to the correction of experimental data and to the absolute calibration of circular transducers by self-reciprocity measurements.” (Author) 14 refs.CrossRefGoogle Scholar
- 1977–266+.Weight, J. P. and Ravenhall, F. W., “An Inexpensive Wideband Recording Facility,” J. Phys. E. (Sci. Instr.) 10 (4), 424–428 (1977). “A series of modifications is described whereby a commercial video tape recorder was adapted for non-TV-format signals. The recorder used had a typical twin-head helical scanning system, with slow-motion and stop-playback capabilities. The signals to be recorded in this case were developed during crack propagation of metal specimens under tension, i.e., stress-wave emissions. These occur at random intervals and are in the frequency range 20 kHz to 2 MHz.” (Author) 3 refs.CrossRefGoogle Scholar
- 1977–267+.Harnik, E., “A Broadband Probe for Studies of Acoustic Surface Waves,” J. Phys. E. (Sci. Instr.) 10 (12), 1217–1218 (1977). “An acoustic surface wave probe has been developed for use in broadband non-destructive testing and in seismological modelling. The probe has a bandwidth of about 0.4–4 MHz but the design is suitable for use up to centre frequencies of about 5 MHz. It takes a negligible amount of energy from the ultrasonic beam and appears to reproduce accurately the shape of an ultrasonic pulse. The probe is characterized by simplicity of construction and operation,” (Author) 6 refs.CrossRefGoogle Scholar
- 1970–268+.Gericke, O. R., “Theory and NDT Applications of Ultrasonic Pulse-Echo Spectroscopy,” Proc. Symp. on the Future of Ultrasonic Spectroscopy, London, October 1970, Paper #1. The author discusses the use of a pulsed swept-frequency system for ultrasonic spectroscopy. The main advantage is that one is able to produce a flat frequency response with such a device. Unfortunately the time resolution and signal-to-noise ratio are both poor. The use of ultrasonic spectroscopy for examining material micro-structure, assessing severity of defects and investigating the frequency-dependence of ultrasonic beam spreading, is reviewed. Many spectra, produced by the author’s apparatus, illustrate the productive uses of spectroscopy.Google Scholar
- 1970–269+.Lloyd, E. A., “Wide-Band Ultrasonic Techniques,” Proc. Symp. on the Future of Ultrasonic Spectroscopy, London, October 1970, Paper #2. Wide-band ultrasonic techniques are categorized as either measurements of distributed phenomena (grain size, etc.) or detection and classification of discrete targets. Furthermore, the target may be non-penetrable (a void) or penetrable. The signals from the penetrable target, being in general the more complex. Response of the defect is approximated by considering only its main scattering features. Discrete scattering centers result in modulations in the magnitude spectrum. Cepstral processing is discussed as a method for extracting defect-size information from the modulated spectrum. The possibility of compact data presentation as the coefficients in a power series expansion (in frequency) of the material’s transfer function is mentioned. Several novel designs for wide-bandwidth transducers are presented.Google Scholar
- 1970–270+.Aldridge, E. E., “Ultrasonic Spectroscopy at the NDT Centre, Harwell: Progress Report,” Proc. Symp. on the Future of Ultrasonic Spectroscopy, London, October 1970, Paper #3. Work to date at Harwell has centered about the design and construction of spectroscopic instrumentation. The importance of gating circuits, with minimal switching transients, for use with analog spectrum analyzers is noted. Problems of signal pick-up from fast digital circuitry is mentioned. The author notes that if the flaw affects frequency components, which are at the same time attenuated by the material surrounding the defect, information concerning the defect may be difficult to extract.Google Scholar
- 1970–271+.Clipson, W. R., “Ultrasonic Spectroscopy Development for Inclusion Cloud Assessment,” Proc. Symp. on the Future of Ultrasonic Spectroscopy, London, October 1970, Paper #4. Frequently, defects occur as “clouds” of small inclusions. Whereas the size of individual defects may be such as to preclude detection, the cloud is detectable. Although no theoretical work is given, experimental spectral measurements (utilizing a wave analyzer) is presented. Spectral differences in the signals from flat-bottom and side-drilled holes were observed, indicating hope for flaw characterization.Google Scholar
- 1970–272+.Mitchell, R. F., “Wide-Band Acoustic Bulk Wave Transducers,” Proc. Symp. on the Future of Ultrasonic Spectroscopy, London, October 1970, Paper #5. Observation that a CdS thin-film transducer gave a flat frequency response led the author to investigate the properties of a transducer with a piezoelectric constant which varies through its thickness. For certain functional relationships of piezoelectric constant versus distance, the transducer’s response will be broadbanded. An interdigital bulk-wave device and a transducer with a shaped back surface also hold possibilities for wide-band response.Google Scholar
- 1942–273+.Mason, W. P., Electromechanical Transducers and Wave Filters, Van Nostrand Co., Inc., New York (1942).Google Scholar
- 1964–274+.Berlincourt, D. A., Curran, D. R., and Jaffee, H., “Piezoelectric and Piezomagnetic Materials and Their Function in Transducers,” Ch. 3 in Physical Acoustics, Vol. I, Part A (W. P. Mason, ed.), Academic Press, New York (1964).Google Scholar
- 1978–275+.Fox, M. D. and Donnelly, J. F., “Simplified Method for Determining Piezoelectric Constants for Thickness Mode Transducers,” J. Acoust.Soc. Am. 64 (5), 1261–1265. “A procedure is described for obtaining the stress constant e
_{33}for an arbitrary piezoelectric transducer operating in the thickness mode. A closed-form solution is developed which uses measurements of the electrical impedance of the transducer as input. Verification of the calculated parameters is accomplished by incorporating them into a computer model of the transducer. A discussion of various methods of obtaining the clamped capacitance C_{0}is included as well as a calculation of an equivalent resistance to represent losses in the ceramic. Numerical examples are presented.Google Scholar - 1972–276+.Papadakis, E. P., “Ultrasonic Diffraction Loss and Phase Change for Broad-Band Pulses,” J. Acoust. Soc. Am. 52 (3), 847–849. “The effective diffraction loss and phase change in the field of broad-band transducers is computed in terms of the normalized distance S
_{c}= zλ_{c}/a^{2}at the center frequency of the pulse. Diffraction corrections for attenuation and velocity are explained, and their limitations stated for broad-band pulses. It is shown that the corrections are functions of bandwidth as well as of S_{c}.” (Author)Google Scholar - 1964–277.Carome, E. F., Parks, P. E., and Mraz, S. J., “Propagation of Acoustic Transients in Water,” J. Acoust. Soc. Am. 36, 946–952. “A technique is described for investigating the propagation of acoustic transients in liquids. Thick piezoelectric plates are employed as acoustic sources and detectors. The results of recent theoretical works on the transient response of such elements are extended to determine the relationships between the time profiles of the voltage applied to the source, the stress wave in the liquid, and the output voltage of the detector. Effects of transient processes in the field of a piston source also are considered. Results are presented of an experimental study of the propagation in water of low-amplitude pressure steps and impulses as narrow as 0.05 μsec. The data are strongly dependent on the parameters of the source-detector configuration. This limits the range of applicability of the technique, but its usefulness for studies of absorbing liquids is indicated.”Google Scholar
- 1970–278.Freedman, A., “Sound Field of Plane or Gently Curved Pulsed Radiators,” J. Acoust. Soc. Am. 48, 221–227. “When a single pulse is applied to a plane radiator in a large rigid baffle or to a convexly curved baffled radiator having dimensions and radii of curvature large compared with the relevant wavelengths, the pressure at a field point is shown theoretically to consist, generally, of a sequence of pulses, each of which is, approximately, a scaled replica of the applied pulse. The number of pulses and their relative size and spacing are functions of position of the field point. In the direction of the main beam, if the radiating surface is plane, these pulses are not resolved and a single nearly undistorted pulse is obtained. A form of reciprocity is shown to exist between the structure of the acoustic signal at a point in the field of a pulsed transducer when transmitting and the structure of the electrical signal when the same transducer receives an acoustic pulse. Simple relationships are presented between the formulas for pulsed radiation, reception, and backscattering from a plane surface.” (Author)Google Scholar
- 1976–279+.Kazhis, R. I. and Lukoshevichyus, A. I., “Wideband Piezoelectric Transducers with an Inhomogeneous Electric Field,” Sov. Phys. Acoust. 22, 167–168. “The bandwidth of piezoelectric transducers is mainly limited by the presence of two sources of ultrasound near the faces of the piezoelectric element and multiple reflections of the generated ultrasonic waves in the transducer. ... We have investigated piezoceramic transducers with an inhomogeneous electric field, for which the distribution of the force lines is determined by a special placement of the working electrodes relative to the crystallographic axes of the piezoelectric.” (Author)Google Scholar
- 1970–280.Stephanishen, P. R., “Transient Radiation from Pistons in an Infinite Baffle,” J. Acoust. Soc. Am. 49, 1629–1638. “An approach is presented to compute the near- and farfield transient radiation resulting from a specified velocity motion of a piston or array in a rigid infinite baffle. The approach, which is based on a Green’s function development, utilizes a transformation of coordinates to simplify the evaluation of the resultant surface integrals. A simple expression is developed for an impulse response function, which is the time-dependent velocity potential at a spatial point resulting from an impulse velocity of a piston of any shape. The time-dependent velocity potential and pressure for any piston velocity motion may then be computed by a convolution of the piston velocity with the appropriate impulse response. The response of an array may be computed using superposition. Several examples illustrating the usefulness of the approach are presented. The farfield time-dependent radiation from a rectangular piston is discussed for both continuous and pulsed velocity conditions. For a pulsed velocity of time duration T it is shown that the pressure at several of the field points can consist of two separate pulses of the same duration, when T is less than the travel time across the piston.” (Author)Google Scholar
- 1974–281.Robinson, D. E., Lees, S., and Bess, L., “Near Field Transient Radiation Patterns for Circular Pistons,” IEEE Trans. Acoust. Speech Sig. Proc. 22 (6), 395–403. “The exact impulse response of field parameters for any field point on or off axis for the case where a circular disc radiator face is subjected to a displacement step corresponding to a velocity impulse is reviewed. By convolution, the transient field pattern for any arbitrary motion of the disc can be obtained. The exact response for a half-sine monopulse is computed. An approximate representation of the transient pressure response to the velocity impulse input at the disc is derived, and it is shown to correspond to the replica pulses described previously. The regions of validity of the approximation are quite limited and the replica pulses are displaced in time from the positions formerly attributable to them. The displaced replica approximation is applied to an examination of the structure of the near field for continuous sinusoidal excitation and a plot of positions of extrema is produced. It is shown that this approximation gives good agreement with the exact values and is superior to the previous published approach in this regard. For short sinusoidal pulses the effect of pulse length on the field pattern, and of field point on the time history of a transient wave are shown. When the excitation is a short sinusoidal pulse the effect of the pulse length and field point position on the field pattern and wave shape are demonstrated.” (Author).Google Scholar
- 1966–282.Kossoff, G., “The Effects of Backing and Matching on the Performance of Piezoelectric Ceramic Transducers,” IEEE Trans. Son. Ultrason. SU-13 (1), 20–30. “The effects of backing and matching on the performance of transmitting and receiving PZT7A transducers working into a water load are analyzed. Although backing widens the bandwidth, it also increases the transmission loss, and more efficient and wider bandwidth transducers are obtained by quarter-wave matching the transducer to the water load. By quarter-wave matching the transducer to low impedance absorbing backings, reflected high impedance absorbing backings may be obtained; and very wide bandwidth and efficient transducers are obtained by quarter-wave matching both to the backing and to the load. In pulse detection applications, the pulse width of these transducers has been found to be nearly independent of such increases in bandwidth. The explanation for this effect and a procedure for determining the approximate echo pulse waveform is presented.” (Author)Google Scholar
- 1972–283.Meeker, T. R., “Thickness Mode Piezoelectric Transducers,” Ultrasonics, 26–36 (January 1972). “This paper is a tutorial review of the theory of the simple thickness mode piezoelectric transducer. The usual differential equations and constitutive relations are used to obtain general impedance equations for the transducer with arbitrary boundary conditions. In the derivations, special attention is given to showing what basic assumptions are made, and which material constants must be used in the equations. As usual, the thickness mode theory is only valid if no quantities depend on the lateral co-ordinates of the plate. It is shown that certain elastic and piezoelectric constants must be zero in the plate co-ordinate system for the simple thickness mode theory to be valid for the transducer. Four geometrical and material variables, and three boundary conditions completely determine the transfer and impedance properties of the transducer. Exact expressions are given for the electrical impedance of the simple thickness mode resonator with free surfaces, and for three electrical properties of a bonded and backed thickness mode transducer (namely, the electrical impedance at low frequency, and the electrical impedance and transfer loss at the halfwave frequency). The transfer loss is 3.3 dB for an unbacked, untuned, and acoustically matched transducer with no series electrical resistance and a piezoelectric coupling factor of 0.5.” (Author)Google Scholar
- 1969–284.Sittig, K. E., “Effects of Bonding and Electrode Layers on the Transmission Parameters of Piezoelectric Transducers Used in Ultrasonic Digital Delay Lines,” IEEE Trans. Son. Ultrason. SU-16 (1), 2–10. “In ultrasonic delay lines with thickness-driven piezoelectric transducers, it is necessary to have electrode and, possibly, bonding layers in the sound transmission path. If these layers have characteristic impedances that are substantially different from those of the piezoelectric transducer and the delay medium, they act as mismatched transmission line sections between the transducer and its load, and transform the normally real load impedance into a complex one. The resulting shifted and deformed response curves are computed for a large number of layer parameters by means of Mason’s equivalent circuit. From these plots, information as to permissible layer thickness, etc., may be obtained and used in the design procedure of ultrasonic delay lines. In digital delay lines, where linear phase response is a design requirement, any intermediate layers should be as thin as possible or be closely matched to the delay medium in order to avoid fast ripples in the frequency response, which would give rise to side lobes far away from the main signal in the time domain.” (Author)Google Scholar
- 1967–285.Sittig, K. E., “Transmission Parameters of Thickness Driven Piezoelectric Transducers Arranged in Multilayer Configurations,” IEEE Trans. Son. Ultrason. SU-14, 167–174. “The individual transducers of an ultrasonic delay line may consist of a multiplicity of piezoelectrically active layers electrically connected in series, parallel, or grouped in series-parallel combinations interspersed with electrically conductive or nonconductive layers of different characteristic acoustic impedances. The stack of transducer layers may be loaded by an absorptive or reactive backing and coupled to the delay medium through bonding and matching layers. The transmission parameters for such configurations are written in a form well suited to digital computation. Inspection of numerical results reveals effects which may be qualitatively understood by visualizing separately the effects due to the mechanical resonances of the layer assembly and those due to the arrangement of piezoelectric material with respect to the stress distribution within the stack. The examples given indicate that transducers consisting of alternately poled stacked A/2 layers of a low coupling factor material such as CdS give an insertion loss improvement at the cost of bandwidth reduction little different from that obtained with narrow-band tuned terminations. For high coupling factor layers, no significant improvement is obtainable.” (Author)Google Scholar
- 1971–286.Mattiat, O. E. (editor), Ultrasonic Transducer Materials, Plenum, New York.Google Scholar
- 1975–287.Martin, R. W. and Sigelmann, R. A., “Force and Electrical Thevenin Equivalent Circuits and Simulations for Thickness Mode Piezoelectric Transducers,” J. Acoust. Soc. Am. 58 (2), 475–489. “A simple model is reported for thickness-mode piezoelectric elements used as ultrasonic transducers in measurement systems. The model represents the excitation system and transducer as a Thevenin mechanical equivalent for the transmitting mode and a Thevenin electrical equivalent for the receiving mode. Computer programs based on the model have been developed, and computer simulations to study the effects of backing materials, element areas, and excitation sources are reported. The nature in which the source impedance alters the Thevenin mechanical output impedance and its importance in determining peak transmission frequency and in computing acoustic coating layers for matching are found. A total transfer improvement of 28 dB was shown for epoxy-backed elements radiating into fluid with the transducer used as both transmitter and receiver by using high values of source and load impedances in contrast to low values. The model was found to agree closely with experimental data of a 2.7-MHz transducer.” (Author)Google Scholar
- 1973–288+.Legros, D. and Lewiner, J., “Electrostatic Ultrasonic Transducers and Their Utilization with Foil Electrets,” J. Acoust. Soc. Am. 53 (6), 1663–1672. “Electrostatic ultrasonic transducers are very attractive when considered from the point of view of simplicity. They are constituted by a condenser, the ultrasonic wave being directly excited on the electrodes. These transducers are currently used at low frequencies (microphones) and sometimes at higher frequencies (up to a few megahertz). At higher frequencies the bias voltage applied across the condenser has to be quite large and electrification of the central dielectric layer can appear. This paper describes such effects and presents the experimental conditions allowing the transducer to operate. The electrification of the dielectric layer is studied and the problems related to the conservation of the deposited charges are considered for Mylar and polypropylene foils of about 10-μ thickness. In the present work the ultrasonic waves generated or received by these transducers have frequencies ranging from 10 to 200 MHz.” (Author)Google Scholar
- 1973–289+.Sessler, G. M. and West, J. E., “Electret Transducers: A Review,” J. Acoust. Soc. Am. 53 (6), 1589–1600. “A review of the history, design, performance, and application of electret transducers is presented. Particular emphasis is placed on foil-electret transducers incorporating a thin-film electret made of Teflon or related materials. Such transducers have excellent frequency response, low distortion, small vibration sensitivity, and have been used over a frequency range extending from 10–3 to 2 × 108 Hz. They can be made in a variety of shapes over, a large range of sizes and are generally not affected by adverse environmental conditions. More than 10 million electret transducers are being manufactured annually as microphones with various directivity patterns for use in amateur and studio applications, tape recorders, sound-measuring instruments, telephone-operators’ headsets, hearing aids, and acoustic-graphic tablets, and as transducers in earphones and phonograph cartridges. Electret transducers are also used for experimental and research applications in such widely different fields as gas analysis, opto-acoustic spectroscopy, aeronautics, atmospheric studies, telephony, ultrasonics, acoustic holography, data transmission, and leak detection in space stations.” (Author)Google Scholar
- 1962–290+.Freedman, A., “A Mechanism of Acoustic Echo Formation,” Acustica 12, 10–21. “Using a method of analysis analogous to that of physical optics, the direct backscattering of small amplitude acoustic waves from a rigid body, immersed in an ideal fluid medium is re-examined. The incident radiation is a pulse of general type, and at long ranges, no restrictions are imposed on the directivity patterns of the transmitting and receiving transducers. Clarification of the echo-formation mechanism applicable at small wavelengths is obtained. The echo is shown to be composed of a number of discrete pulses, each a replica of the transmission pulse, and hence termed an ‘image pulse.’ An image pulse is generated whenever there is a discontinuity with respect to range, r, in dnW(r)/drn, where W(r) is the solid angle subtended at the transducers by that part of the scattering body within range r. n may be zero or any positive integer. It is shown that four types of echo envelope arise from varying degrees of overlap of these image pulses. The combination of ‘image pulse’ and ‘creeping wave’ mechanisms is believed to account for the main scattering phenomena from rigid convex bodies, the former mechanism being paramount outside the shadow region at small wavelengths, the latter mechanism predominating at large wavelengths.” (Author) 7 refs.Google Scholar
- 1960–291.Filipczynski, L., “Transients and the Equivalent Electrical Circuit of a Piezoelectric Transducer,” Acustica 10, 149. “The subject of the present paper is an X-cut quartz transducer, in which one-dimensional mechanical vibrations are discussed. Starting with piezoelectric equations in terms of the electrical enthalpy, transients of the transducer, frequency-response characteristics and the input impedance are analyzed. The results of experiments confirm the described mechanism of the vibrations in the transducer, as well as the frequency-response characteristics. On the basis of the results obtained, an equivalent electrical circuit of the transducer has been constructed in terms of a transmission line. The given circuit is valid for steady states and for transients as well.” (Author)Google Scholar
- 1974–292.Beaver, W. L., “Sonic Nearfields of Pulsed Piston Radiators,” J. Acoust. Soc. Am. 56, 1043–1048. “The formation of sonic pulses in the nearfield region of a pulsed piston radiator has been investigated by similation on a digital computer. The results give insight into the sonic radiation process, showing the formation of pulses that replicate the piston motion, with trailing disturbances which originate from the rim. A comparison is made between pulsed and CW beam profiles, showing that there is little difference for moderate pulse lengths.” (Author)Google Scholar
- 1975–293+.Tabuchi, D., Inoue, N., Okuwa, T., and Ohno, K., “Ultrasonic Spectroscopy and Automatic Ultrasonic Spectrometer,” Acustica 32, 236–243. “An automatic recording ultrasonic spectrometer has been constructed in order to measure and record the frequency spectra of ultrasonic absorption and velocity. For the measurement of absorption an ultrasonic pulse echo method is used, and an ultrasonic pulse circulation method is applied for the measurement of velocity. The data of absorption and velocity are punched on a tape, and typed. If the tape is put into a digital computer, the ultrasonic spectra and the characteristic values are computed, punched on a tape, and typed. When the tape is put into the ultrasonic spectrometer, the ultrasonic spectra of absorption and velocity are recorded by a digital plotter. The process is completely automated by a method of sequence control.” (Author) 6 refs.Google Scholar
- 1971–294+.Papadakis, E. P. and Fowler, K. A., “Broadband Transducers: Radiation Field and Selected Applications,” J. Acoust. Soc. Am. 50 (3), 729–745. “In many applications, broad-band ultrasonic transducers capable of producing short video pulses are required. Previously, plane-wave analysis with equivalent circuits has proven successful in predicting pulse shape in the time and frequency domains. The present approach is to recognize that piston sources radiate nonplanar waves, and that the frequency spectrum of a broad-band piston source can be measured experimentally. With the spectrum as a weighing function for the field profiles of a monofrequency piston source, a superposition is performed to find the pressure and phase profiles in the radiation field of a broad-band transducer. Experimental measurements are presented that take advantage of the broad-band pulse technique combined with spectrum analysis. These include thickness gauging of thin materials and interface layers, and relative viscosity measurements.” (Author)Google Scholar
- 1971–295+.Papadakis, E. P., “Effects of Input Amplitude Profile Upon Diffraction Loss and Phase Change in a Pulse-Echo System,” J. Acoust. Soc. Am. 49 (1), 166–168. “The particle velocity profile V(p) across the face of a transmitting transducer is shown to have large effects upon the diffraction loss and phase change in the ultrasonic field of the transducer. Various functions V(p), monotonic decreasing from the center to the rim of a circular transducer, were employed. The pulse-echo response of the transducer was calculated by numerical integration on an electronic computer. It was found that the functions V(p) chosen caused the diffraction-loss and phase-change curves to be smoother than in the piston case and caused the respective peaks and plateaus to shift with distance in the Fresnel region.” (Author)Google Scholar
- 1960–296+.Brekhovskikh, L. M., Waves in Layered Media, Academic Press, New York (translated from the Russian by D. Lieberman and edited by R. T. Beyer).Google Scholar
- 1963–297+.Redwood, M., “A Study of Waveforms in the Generation and Detection of Short Ultrasonic Pulses,” Appl. Mat, Res. 2, 76–84. “Investigations of the properties of materials frequently make use of short ultrasonic pulses consisting of from one to about ten oscillations which are roughly sinusoidal in shape. The ultrasonic signal is usually generated by applying an electrical signal to a piezoelectric transducer. After passing through the material under investigation it is detected by using a second piezoelectric transducer. The nature of the electrical waveforms observed in such experimental systems and their relation to the ultrasonic signal is frequently not well understood, as they are dependent on a complex combination of circumstances involving (1) the thickness of the transducers, (2) the acoustic impedances of the materials in contact with both faces of each transducer, and (3) the nature of the electrical resistance into which the receiving transducer feeds. Sometimes the pulse shape is also considerably affected by the nature of the material under investigation, particularly if this material is highly absorbent. Lack of understanding of the change in shape of the waveform which can be produced, particularly by the receiving transducer, frequently leads to misconceptions concerning the actual shape of the ultrasonic pulse and its frequency spectrum. This may also lead to considerable errors in estimates of its velocity and attenuation. The generation and detection of ultrasonic pulses by using piezoelectric transducers are treated here in some detail. Methods of predicting the various ultrasonic and electrical waveforms are developed and illustrated by application to a particular system designed for the measurement of velocity in small samples of material and hence using as short an ultrasonic pulse as possible.” (Author) 3 refs.Google Scholar
- 1978–298+.Simpson, W. A., Jr., “A Microcomputer-Controlled Ultrasonic Data Acquisition System,” Oak Ridge National Laboratory Tech. Memo 0RNL/TM6531. “The large volume of ultrasonic data generated by computer-aided test procedures has necessitated the development of a mobile, high-speed data acquisition and storage system. This approach offers the decided advantage of on-site data collection and remote data processing. It also utilizes standard, commercially available ultrasonic instrumentation. This system is controlled by an Intel 8080A microprocessor. The MCS80-SDK microcomputer board was chosen, and magnetic tape is used as the storage medium. A detailed description is provided of both the hardware and software developed to interface the magnetic tape storage subsystem to Biomation 8100 and Biomation 805 waveform recorders. A boxcar integrator acquisition system is also described for use when signal averaging becomes necessary. Both assembly language and machine language listings are provided for the software.” (Author)Google Scholar
- 1976–299.Robinson, D. E. and Williams, B. G., “Digital Acquisition and Interactive Processing of Ultrasonic Echoes,” Ultrasound in Med. and Biol. 2, 199–212. “The requirements for an interactive digital signal processing system for ultrasonic pulse-echo signals are discussed. A system based on an Interdata Model 80 mini-computer and micro-processor interface is described. The system is capable of acquiring ultrasonic data at a sampling rate of 6 MHz. Ultrasonic B-mode data may be acquired in Line Mode, when echo waveform data and transducer position and orientation are stored, or in Section Mode when the data is converted directly into picture form in memory in the same way that a standard echogram is formed on the screen of an oscilloscope. In each case the data for single complete high resolution echogram may be acquired in less than 15 sec. It is shown that the 6 MHz sampling rate is sufficient to faithfully preserve the echo waveshape of a 2 MHz system independently of the relation to the phase of the sampling. Also shown is a cross-sectional echogram of the pregnant uterus, and its digital representation with a raster density of 80 × 100 and 160 × 200 picture elements. The computer is programmed with an interactive program to allow ultrasonic signals to be acquired, stored, processed and examined with the convenience of a desk calculator. Sample operations are illustrated including data interpolation, spectrum analysis, filtering and complex signal deconvolution. The ability of deconvolution techniques to resolve targets separated by less than one wavelength in depth is demonstrated. Possibilities of further processing techniques are outlined.” (Author) 20 refs.Google Scholar
- 1978–300.Elsley, R. K., “Accurate Ultrasonic Measurements with the Biomation 8100 Transient Recorder,” Proc. First Intl. Symp. on Ultrason. Mat. Characterization, June 1978. “The Biomation 8100 Transient Recorder performs 8-bit analog-to-digital (A/D) conversions at a 100 MHz sample rate and is widely used for data acquisition of high frequency ultrasonic signals. Due to the nature of the A/D method used, the accuracy is substantially less than 8-bits under some conditions, particularly at high frequencies. The errors which occur are found to be partially random and partially systematic (called “preferred states” by the manufacturer). The accuracy which can be obtained depends not only on the signal which is being acquired, but also on what features of that signal the experimenter is interested in measuring. By using signal averaging and offset variation, dynamic ranges in excess of 70 dB (12-bits) have been obtained, and subtle but important features in the signals being analyzed have been thereby measured.” (Author) 1 ref.Google Scholar
- 1956–301.Ying, C. F. and Truell, Rohn, “Scattering of a Plane Longitudinal Wave by a Spherical Obstacle in an Isotropically Elastic Solid,” J. Appl. Phys. 27, 1086–1097 (1956). The first consideration of the scattering of an acoustic wave propagating in a solid.Google Scholar
- 1960–302.Einspruch, Norman G., Witterholt, E. J., Truell, Rohn, “Scattering of a Plane Transverse Wave by a Spherical Obstacle in an Elastic Medium,” J. Appl. Phys. 31, 806–818 (1960). A consideration of the scattering of a shear wave by a spherical discontinuity.CrossRefzbMATHMathSciNetGoogle Scholar
- 1965–303.Johnson, Gregert and Truell, Rohn, “Numerical Computations of Elastic Scattering Cross Sections,” J. Appl. Phys. 36, 3466–3475 (1965). A brief review of the calculation of cross section expressions for the scattering of an elastic wave in an elastic medium, with numerical calculations.CrossRefGoogle Scholar
- 1975–304.Gubernatis, J. E., Domany, E., Huberman, M. and Krumhansl, J. A., “Theory of the Scattering of Ultrasound by Flaws,” Proc. 1975 IEEE Ultrason. Symp., 107–110. “An integral equation governing the scattering of ultrasound by an arbitrarily shaped flaw is presented, and features of the scattered displacement and stress fields are discussed for the case of a flaw embedded in an isotropic medium. Also discussed are differential cross sections for the scattered power. These cross sections for a spherical flaw (cavity and inclusion) are evaluated by an approximation analogous to the first Born approximation in quantum mechanical scattering. The results of the calculations are compared with exact results for scattering of ultrasound by spheres. The relevance of this comparison to NDE, i.e., flaw identification, is discussed.” (Author) 3 refs.Google Scholar
- 1958–305.White, R. W., “Elastic Wave Scattering at a Cylindrical Discontinuity in a Solid,” J. Acoust. Soc. Am. 30, 771–785 (1958). Deals with the scattering of plane compressional and shear waves at oblique incidence on an infinite elastic rod embedded in another isotropic elastic medium. It pays particular attention to mode conversion. It also reports some measurements.CrossRefGoogle Scholar
- 1948–306.Fridman, M. M., “The Diffraction of a Plane Elastic Wave by a Semi-Infinite Rigid Plane,” Dokl. Akad. Nauk. USSR 60, 1145–1148 (1948), (in Russian). The first solution for scattering from a two-dimensional flaw.zbMATHMathSciNetGoogle Scholar
- 1953–307.Maue, A.-W., “Die Bengung Elasticher Wellen an der Halbebene,” Z. F. Ang. Math. and Mech. 33, 1–10 (1953). An exact reduction to quadratures of the two-dimensional problem of elastic scattering of an infinite half-plane weak crack. The differential wave equations and boundary conditions are combined into integral equations for the potentials, which are represented as plane-wave superpositions. The integral equations are solved by the method of Clemmow. (In German.)CrossRefzbMATHMathSciNetGoogle Scholar
- 1964–308.Ang, D. D. and Knopoff, L., “Diffraction of Scalar Elastic Waves by a Clamped Finite Strip,” Proc. N.A.S. 51, 471–476 (1964). The long-wavelength limit to the solution of the far field for the title problem.CrossRefzbMATHMathSciNetGoogle Scholar
- 1964–309.Ang, D. D. and Knopoff, “Diffraction of Scalar Elastic Waves by a Finite Crack,” Proc. N.A.S. 51, 593–598 (1964). Similar to (308) except that the strip has weak boundary conditions (weak crack), which is a more important problem in applications.CrossRefzbMATHMathSciNetGoogle Scholar
- 1964–310.Ang, D. D. and Knopoff, L., “Diffraction of Vector Elastic Waves by a Clamped Finite Strip,” Proc. N. A. S. 52, 201–207 (1964). An extension of the calculation of (308).CrossRefMathSciNetGoogle Scholar
- 1964–311.Ang, D. D. and Knopoff, L., “Diffraction of Vector Elastic Waves by a Finite Crack,” Proc. N.A.S. 52, 1075–1081 (1964). This paper considers the problem of the diffraction of an incident plane longitudinal wave by a finite crack, and evaluates the far fields by the method of steepest descents.CrossRefzbMATHMathSciNetGoogle Scholar
- 1976–312.Tan, T. H., “Theorem on the Scattering and the Absorption Cross Section for Scattering of Plane, Time-Harmonic, Elastic Waves,” J. Acoust. Soc. Am. 59, 1265–1267 (1976). A method, due to de Hoop, is extended to the scattering of elasto-dynamic waves to derive the “cross-section theorem” (the optical theorem).CrossRefzbMATHGoogle Scholar
- 1977–313.Varatharajulu, V., “Reciprocity Relations and Forward Amplitude Theorems for Elastic Waves,” J. Math. Phys. 18, 537–543 (1977). This paper derives the forward scattering (optical) theorem and receiprocity relations (including polarization change on scattering) for plane, monochromatic elastic waves scattered by obstacles of arbitrary shape. *Now Varadan.CrossRefzbMATHGoogle Scholar
- 1977–314.Gubernatis, J. E., Domany, E., and Krumhansl, J. A., “Formal Aspects of the Theory of the Scattering of Ultrasound by Flaws in Elastic Materials,” J. Appl. Phys. 48, 2804–2811 (1977). This paper considers the general theory of the scattering of ultrasound by flaws. It considers an incident plane wave scattering from a single homogeneous flaw in an isotropic elastic medium, and obtains an integral equation to describe the problem. The integration is over a volume, and this appears to be the first report to present the volume formulation for elasticity in a reasonably complete form. It derives expressions for scattered amplitudes and differential cross sections, and an optical theorem.CrossRefGoogle Scholar
- 1977–315.Tan, T. H., “Reciprocity Relations for Scattering of Plane, Elastic Waves,” J. Acoust. Soc. Am. 61, 928–931 (1977). Reciprocity relations for scattering of plane, elastic waves incident upon a finite, linear, reciprocal obstacle in a homogeneous, isotropic, perfectly elastic medium are investigated.CrossRefzbMATHGoogle Scholar
- 1976–316.Pao, Yih-Hsing and Mow, C. C, “Theory of Normal Modes and Ultrasonic Spectral Analysis of the Scattering of Waves in Solids,” J. Acoust. Soc. Am. 59, 1046–1056 (1976). A theory of the spectral analysis of the scattering of elastic waves is presented and illustrated with numerical results for the scattering by a circular cylindrical fluid inclusion in a solid. From overtone frequencies the ratio of the wave speed to the radius of the inclusion can be determined. The application of this technique to nondestructive testing is discussed.CrossRefzbMATHGoogle Scholar
- 1976–317.Pao, Yih-Hsing and Varatharajulu, Vasundara, “Huygens’ Principle, Radiation Conditions, and Integral Formulas for the Scattering of Elastic Waves,” J. Acoust. Soc. Am. 59, 1361–1371 (1976). By using the divergence theorem this paper shows how Helmholtz- and Kirchhoff-type integral formulas can be derived. Both “interior” and “exterior” formulas are obtained; these formulas are necessary for investigating the scattering of elastic waves by bounded objects. The results illustrate Huygens’ principle for the two wave fronts of the elastic wave field. *Now Varadan.CrossRefzbMATHMathSciNetGoogle Scholar
- 1977–318.Gubernatis, J. E., Domany, E., Krumhansl, J. A., and Huberman, M., “The Born Approximation in the Theory of Scattering of Elastic Waves by Flaws,” J. Appl. Phys. 48, 2812–2819 (1977). The integral equation formulation obtained in 77–1 is used to derive an approximation scheme, which may be applied relatively easily to scatterers of complicated shapes. The approximation works best for backscattered long waves, but in certain cases is surprisingly good even for short wavelengths and all angles.CrossRefGoogle Scholar
- 1959–319.Karal, Frank C., Jr., and Keller, Joseph B., “Elastic Wave Propagation in Homogeneous and Inhomogeneous Media,” J. Acoust. Soc. Am. 31, 694–705 (1959). This is the extension of Keller’s geometrical theory of diffraction to elastic waves. It gives a general method for solving linearized elastic-wave problems which does not depend on the possibility of separation of variables. The method should work well for short wavelengths, but experience had shown that it was still useful for wavelengths of the same order of magnitude as other dimensions in the problem.CrossRefMathSciNetGoogle Scholar
- 1978–320.Weight, J. P. and Hayman, A. J., “Observations of the Propagation of Very Short Ultrasonic Pulses and Their Reflection by Small Targets,” J. Acoust. Soc. Am. 63 (2), 396–404. “The field of a circular ultrasonic transducer emitting a single-cycle pulse into water has been observed using a specially constructed small (150 ym) wide-band receiving probe and a compact stroboscopic schlieren system. The theoretically predicted plane-wave and diffracted edge-wave components of the field have been resolved. Good agreement with the theory for a pistonlike source is obtained, except in a region less than 1.5 transducer radii from the transducer. The output of the transducer used in the transmit-receive mode to detect small targets has been measured and the results are in accord with a time-domain principle of reciprocity between transmission and reception. Implications of the results for field plotting and for the location and characterization of small targets are considered.” (Author) 27 refs.Google Scholar
- 1975–321.Richardson, J. M. and Tittmann, B. R., “Deducing Subsurface Property Gradients from Surface Wave Dispersion Data,” Proc. 1975 IEEE Ultrason. Symp., 488–491. “Because of the ill-posed nature of the problem, special mathematical techniques must be used to convert surface wave dispersion data into subsurface property measurement. The solution is approached here within the framework of estimation theory. This approach starts with a mathematical model giving a probabilistic description of the possible results of measurement and then the optimal estimate is obtained as the most probable value within the constraints imposed by the actual measurements. Estimation theory also yields auxiliary measures pertaining to bias, data vs. model dominance, resolution and a posteriori variance. The theory is applied to actual experimental data consisting of the phase velocities of Rayleigh surface waves in surface-hardened steel at a set of four wavelengths. The estimated profile of hardening is compared with independent destructive measurements. As a test, the theory is also applied at the same set of wavelengths to a set of synthetic data calculated from an assumed profile. The above auxiliary measures giving properties of the estimator are also discussed.” (Authors) 5 refs.Google Scholar
- 1978–322.Lewis, D. K., Szilas, P., Fitting, D. W., and Adler, L., “Spectrum Analysis of Elastic Wave Scattering from Cracks in Metals,” J. Acoust. Soc. Am. 63, Suppl. No. 1, 974. Here experiments are compared to Keller’s theory for elastic wave diffraction, with Maue’s solution serving as the canonical problem.Google Scholar
- 1977–323.Achenbach, J. D. and Gautesen, A. K., “Geometrical Theory of Diffraction for Three-D Elastodynamics,” J. Acoust. Soc. Am. 61, 413–421. Here Keller’s geometrical diffraction theory is applied to three-dimensional elastodynamics, particularly to the diffraction of longitudinal waves by a crack. This yields approximations useful for large frequencies and/or large distances from the crack edge. As an example the diffraction of a point-source field by a semi-infinite crack is worked out in detail.Google Scholar
- 1978–324.Gautesen, A. K., Achenbach, J. D., and McMaken, H., “Surface-Wave Rays in Elastodynamic Diffraction by Cracks,” J. Acoust. Soc. Am. 63, 1824–1831. This is the first study of the contributions to the diffracted fields which come, not from diffracted rays of longitudinal and transverse motion, but from rays of surface waves. These provide the main contributions on the faces of the crack. As an example the problem of a plane longitudinal wave normally incident on a penny-shaped crack is worked out in some detail.Google Scholar
- 1977–325.Datta, S. K., “Diffraction of Plane Elastic Waves by Ellipsoidal Inclusions,” J. Acoust. Soc. Am. 61, 1432–1437. The method of matched asymptotic expansions is used to get a low-frequency solution for the diffraction of a plane wave by an elastic ellipsoidal inclusion. Numerical results are given, and applicability to NDE is discussed.Google Scholar
- 1976–326.Waterman, P. C., “Matrix Theory of Elastic Wave Scattering,” J. Acoust. Soc. Am. 60, 567–580. Earlier developments of a matrix theory for acoustic and EM scattering are here extended by their developer to elastic waves. If certain matrix elements which express mode conversion are set to zero, the elastic matrix equations reduce to a superposition of acoustic and EM equations, providing a unified theory of scattering of acoustic, EM and elastic waves by an obstacle of arbitrary geometry and making available the entire body of acoustic and EM results to compare the elastic theory with. The matrices are symmetric and unitary.Google Scholar
- 1976–327.Varatharajulu, V.,* and Pao, Y.-H., “Scattering Matrix for Elastic Waves. 1. Theory,” J. Acoust. Soc. Am. 60, 556–566. This paper extends the already existing scattering matrix approach of Waterman to the scattering of elastic waves. The method is applicable to obstacles of arbitrary shape so one does not have to calculate a special set of wave functions for each geometry. The matrices are symmetric and unitary, which is very nice because these properties are essential for checking the numerical accuracy. *Now Varadan.Google Scholar
- 1978–328.Waterman, P. C, “Matrix Theory of Elastic Wave Scattering. II. A New Conservation Law,” J. Acoust. Soc. Am. 63, 1320–1325. A new conserved elastodynamic field quantity is found; this new conservation requirement may lead to deeper physical understanding and to simpler computational methods using the scattering-matrix theory.Google Scholar
- 1978–329.Varadan, Vasundara V., “Scattering Matrix for Elastic Waves. II. Application to Elliptic Cylinders,” J. Acoust. Soc. Am. 63, 1014–1024. The scattering-matrix approach to elastic wave scattering is here employed to give numerical results for scattering of obliquely-incident plane waves from a cylinder of elliptic cross section. It is much more useful for short wavelengths than for long.Google Scholar
- 1978–330.Varadan, Vijay K., Varadan, Vasundara V., and Pao, Yih-Hsing, “Multiple Scattering of Elastic Waves by Cylinders of Arbitrary Cross Section. I. SH Waves., J. Acoust. Soc. Am. 63, 1310–1319. The problem here is many identical, long, parallel randomly distributed cylinders of arbitrary cross section, scattering time-harmonic polarized plane shear waves. The method combines the scattering-matrix approach and a statistical averaging technique. Numerical results are presented.Google Scholar
- 1972–331.Boore, David M., “Finite Difference Methods for Seismic Wave Propagation in Heterogeneous Materials,” Methods in Computational Physics 11, 1–37. A review article on the computation of elastic wave propagation in media whose properties change with position, by finite difference methods.Google Scholar
- 1972–332.Lysmer, John and Drake, Lawrence A., “A Finite Element Method for Seismology,” Methods in Computational Physics 11, 181–216. A presentation of a finite element method for surface waves which pays attention to computational feasibility.Google Scholar
- 1976–333.Datta, S. K., “Scattering of Elastic Waves by a Distribution of Inclusions,” Arch. Mech. Stos. 28, 317–324. The problem of scattering of plane P-waves off a uniform distribution of rigid spheroids is treated by combining the method of matched asymptotic expansions and a suitable configurational averaging method.Google Scholar
- 1975–334.Vary, A., “Feasibility of Ranking Fracture Toughness by Ultrasonic Measurements,” Proc. 1975 IEEE Ultrason. Symp., 588–590. “Preliminary experimental verification was made of the expected correlation between ultrasonic attenuation parameters and fracture toughness measurements on a set of maraging steel specimens. An empirical equation is proposed for relating the fracture toughness property K
_{c}to the ultrasonic properties of a polycrystalline solid. The pertinent ultrasonic factors in this case involve the attenuation coefficient a, frequency f, and 3, the slope of the a vs. f curve. The proposed relation has the form K_{c}= ∅β_{f}. It predicts that the fracture toughness property K_{c}will be proportional to the attenuation slope 3 evaluated over an appropriate frequency range. The results of this feasibility study with maraging steel specimens indicate that if various specimens of a given metal possess different fracture toughness, it is possible to rank them in order of toughness by ultrasonic testing.” (Author) 9 refs.Google Scholar - 1976–335.Sobczyk, K., “Elastic Wave Propagation in a Discrete Random Medium,” Acta Mechanica 25, 13–28. This paper considers propagation of elastic waves in an infinite solid containing a random configuration of identical finite scatterers. The work was stimulated by practical questions in geophysics and ultrasonic spectroscopy. It gives a general formulation for scatterers of arbitrary shape, and solutions for specific cases of spherical scatterers. The English has a Polish flavor.Google Scholar
- 1974–336.Keer, L. M. and Luong, W. C., “Diffraction of Waves and Stress Intensity Factors in a Cracked Layered Composite,” J. Acoust. Soc. Am. 56, 1681–1686. Layers in composite materials act somewhat as waveguides; this study considers the effect of a crack perpendicular to the layer, and shows that it gives rise to scattered waves in the layer which could be detected at a large distance from the flaw.Google Scholar
- 1975–337.Keer, L. M., Luong, W. C. and Achenbach, J. D., “Elastodynamic Stress Intensity Factors for a Crack in a Layered Composite,” J. Acoust. Soc. Am. 58, 1204–1210. This studies the effect of a. crack parallel to the layer (cf. 74–2); the ease of detection of the flaw depends on the stiffness of the layer, with flaws in relatively stiff layers being harder to detect.Google Scholar
- 1974–338.Christensen, R. M., “Wave Propagation in Elastic Media with a Periodic Array of Discrete Inclusions,” J. Acoust. Soc. Am. 55, 700–707. This studies the propagation of waves in a homogeneous, isotropic medium containing an array of discrete inclusions of another material. Full account is taken of multiple scatterings. The direction of propagation is restricted to be one of the symmetry directions of the material (which has cubic symmetry). A perturbation method is used.Google Scholar
- 1978–339.Simons, Donald A., “Reflection of Rayleigh Waves by Strips, Grooves and Periodic Arrays of Strips or Grooves,” J. Acoust. Soc. 63, 1292–1301. Devices incorporating grooves and strips are used to perform certain microwave signal-processing applications, and this is the most recent paper on the title problem, with references to earlier work. Integral equations are solved by perturbation techniques.Google Scholar
- 1978–340.Gaunard, G. C. and H. Uberall, “Theory of Resonant Scattering from Spherical Cavities in Elastic and Viscoelastic Media,” J. Acoust. Soc. Am. 63, 1699–1712. This paper studies theoretically the scattering of a plane p-wave by a fluids-filled spherical cavity in elastic and viscoelastic (hence absorbing) media. The approach, new to elastodynamics and acoustics, is familiar in nuclear scattering theory. Numerical computations are presented.Google Scholar
- 1977–341.Tan, T. H., “Scattering of Plane, Elastic Waves by a Plane Crack of Finite Width,” Appl. Sci. Res. 33, 75–100. This paper considers the diffraction of time-harmonic, vertically polarized (the problem involving horizontally polarized waves has already been dealt with extensively in the literature), plane elastic waves by a crack of finite width using the integral-equation method. Numerical solutions are presented.Google Scholar
- 1976–342.Tan, T. H., “Diffraction of Time-Harmonic Elastic Waves by a Cylindrical Obstacle,” Appl. Sci. Res. 32, 97–144. An integral equation formulation of the diffraction of two-dimensional elastic waves by a cylindrical obstacle is presented. For a number of configurations the integral equations are solved numerically. Also numerical results on power scattering and extinction cross sections are given.Google Scholar
- 1975–343.Rose, Joseph L. and Paul A. Meyer, “Model for Ultrasonic Field Analysis in Solids,” J. Acoust. Soc. Am. 57, 598–605. “This paper concentrates on one of the most basic ultrasonic problems in NDT: that of evaluating the ultrasonic field characteristics in a solid material resulting from a pulsed piezoelectric crystal” (authors). It presents a theoretical model that can be used to evaluate analytically ultrasonic transducer longitudinal wave-generation characteristics in homogeneous isotropic solids. Results depend on the spectrum of the input pulse.Google Scholar
- 1974–344.Chow, T. S., “Scattering of Elastic Waves in an Inhomogeneous Solid,” J. Acoust. Soc. Am. 56, 1049–1051. Plane harmonic elastic waves are propagating in an isotropic material containing randomly distributed inhomogeneities; results are expressed in terms of correlation functions.Google Scholar
- 1976–345.Israilov, M. Sh., “Certain Exact Solutions to Problems of Diffraction of Elastic Waves at a Segment,” Sov. Phys. Dokl. 21, 756–757 (from DAN SSSR 231, 1074–1076). Exact solutions for particular cases of diffraction of longitudinal and transverse waves in elastic media are given; one problem corresponds to diffraction at a rigid plate, another to diffraction at a slit. These are for transient plane waves.Google Scholar
- 1971–346.Kraft, David W., and Michael C. Franzblau, “Scattering of Elastic Waves from a Spherical Cavity in a Solid Medium,” J. Appl. Phys. 42, 3019–3024. This is extending the work of Truell and his collaborators; it gives the first numerical computations of the scattering cross section for an incident transverse wave.Google Scholar
- 1963–347+.Bogert, B. P., Healy, M. J. R., and Tukey, J. W., “The Frequency Analysis of Time Series for Echoes: Cepstrum, Pseudo-Autocovariance, Cross-Cepstrum and Saphe Cracking,” Chapter 15 in Time Series Analysis, Rosenblatt (editor), Wiley (1963). The authors introduce the technique of cepstral processing. The use of this method for detecting time separation of “echoes” in the presence of various sources of noise is explored.Google Scholar
- 1969–348+.Cooley, J. W., Lewis, P. A. W., and Welch, P. D., “The Fast Fourier Transform and its Applications,” IEEE Trans. Educ. E-12 (1), 27. “The advent of the fast Fourier transform method has greatly extended our ability to implement Fourier methods on digital computers. A description of the algorothm and its programming is given here and followed by a theorem relating its operands, the finite sample sequences, to the continuous functions they often are intended to approximate. An analysis of the error due to discrete sampling over finite ranges is given in terms of aliasing. Procedures for computing Fourier integrals, convolutions and lagged products are outlined” (author). A FORTRAN subroutine is given for computing the discrete Fourier transform by the FFT method.Google Scholar
- 1967–349+.Singleton, R. C, “A Method for Computing the Fast Fourier Transform with Auxiliary Memory and Limited High-Speed Storage,” IEEE Trans. Audio Electroacoust. AU-15, 91–97. “A method is given for computing the fast Fourier transform of arbitrarily large size using auxiliary memory files, such as magnetic tape or disk, for data storage. Four data files are used, two in and two out. A multivariate complex Fourier transform of n = 2m data points is computed in m passes of the data, and the transformed result is permuted to normal order by m-1 additional passes. With buffered input-output, computing can be overlapped with reading and writing of data. Computing time is proportional to n log2 n. The method can be used with as few as three files, but file passing for permutation is reduced by using six or eight files. With eight files, the optimum number for a radix 2 transform, the transform is computed in m passes without need for additional permutation passes. An ALGOL procedure for computing the complex Fourier transform with four, six, or eight files is listed, and timing and accuracy test results are given. This procedure allows an arbitrary number of variables, each dimension a power of 2” (author).Google Scholar
- 1969–350+.Singleton, R. C, “An Algorithm for Computing the Mixed Radix Fast Fourier Transform,” IEEE Trans. Audio Electroacoust. AU-17, 93–103. “This paper presents an algorithm for computing the fast Fourier transform, based on a method proposed by Cooley and Tukey. As in their algorithm, the dimension n of the transform is factored (if possible), and n/p elementary transforms of dimension p are computed for each factor p of n. An improved method of computing a transform step corresponding to an odd factor of n is given; with this method, the number of complex multiplications for an elementary transform of dimension p is reduced from (p-1)2 to (p-l)2/4 for odd p. The fast Fourier transform, when computed in place, requires a final permutation step to arrange the results in normal order. This algorithm includes an efficient method for permuting the results in place. The algorithm is described mathematically and illustrated by a FORTRAN subroutine” (Author).Google Scholar
- 1975–351.Burgess, J. C., “On Digital Spectrum Analysis of Periodic Signals,” J. Acoust. Soc. Am. 58 (3), 556–567. “Digital spectrum analysis of harmonic signals can result in amplitude estimates in error as much as 3.92 dB. The corresponding frequency estimates are not exact. The paper presents a general method for obtaining significantly improved estimates of amplitude and frequency. Criteria are given which allow specification of an error limit. Specific equations are given for sample signals that are unmodified (open window) and for signals modified by a Hamming data window. The phenomenon called “leakage” is shown to result from discontinuities imposed by the computation process at the periodically extended “ends” of a sample signal and not, as is often supposed, by discontinuities presumed to exist (but do not) at the “ends” of the open window. Criteria for window selection to reduce leakage are discussed. Calibration is specifically treated. When any data window other than the open window is used, a different calibration must be applied to periodic and random components in a signal. Although discussion is limited to a single harmonic signal, the method can be applied in a straightforward way to signals with multiple harmonics” (Author) 32 refs.Google Scholar
- 1966–352+.Gauster, W. B. and Breazeale, M. A., “Detector for Measurement of Ultrasonic Strain Amplitudes in Solids,” Rev. Sci. Instrum. 37 (11), 1544–1548. “A capacitive detector has been developed for strain amplitude measurements of longitudinal ultrasonic waves in the frequency range from 5 to 100 MHz. The sensitivity of the device is such that displacement amplitudes of the order of 10–10 cm can be detected. As a check of the technique, quantitative measurements of the harmonic distortion of ultrasonic waves in a single crystal of germanium were made. From the results, some combinations of third-order elastic constants are calculated and are compared with values obtained with the same sample by another method” (authors) 11 refs.Google Scholar
- 1977–353+.Cantrell, J. H., Jr. and Breazeale, M. A., “Elimination of Transducer Bond Corrections in Accurate Ultrasonic Wave Velocity Measurements by Use of Capacitive Transducers,” J. Acoust. Soc. Am. 61 (2), 403–406 “A capacitive-driver-capacitive detector system for generation and detection of ultrasonic waves has been developed. This eliminates the necessity of bonding piezoelectric transducers to solid samples. With the capacitive-driver-capacitive-detector system, free-free boundary conditions exist at the sample surfaces and longitudinal ultrasonic-wave velocities in solids can be measured accurately without correcting for ultrasonic-wave phase shifts due to sample-bonded transducer interfaces. The capacitive driver has a mica dielectric which increases the breakdown potential, but maintains the free-free boundary conditions at the solid specimen surfaces. This allows for a larger-amplitude ultrasonic signal to be generated in the sample than is possible with an air-gap capacitive driver. This improves the precision of the measurement. The accuracy of the method is comparable with that of bonded-transducer methods, after bond corrections are made” (author) 14 refs.Google Scholar
- 1971–354.Kazys, R. J. and Domarkas, V., “The Frequency and Transient Response of Piezotransducers with Intermediate Layers and Electrical Matching Circuits,” Proc. 7th Int. Congress on Acoustics, Session 25U3 (Budapest, 1971). “This investigation includes the action of intermediate layers, backing and electrical matching circuits on frequency and transient responses of thickness vibrating piezotransducers operating in liquids . . . Consideration is given to frequency and phase response of the system piezotransmitter-piezoreceiver ...” (author) 5 refs.Google Scholar
- 1977–355.Kazys, R. and Lukosevicius, A., “Optimization of the Piezoelectric Transducer Response by Means of Electrical Correcting Circuits,” Ultrasonics, 111–116 (May 1977). “A method of shortening the transient response of a piezoelectric transducer is described. It can be applied to thickness mode piezoelectric transducers of arbitrary electromechanical coupling. The system incorporates electrical correcting circuits and can produce a transient response with a duration much shorter than the transit time of an ultrasonic wave traveling through the piezoelectric plate” (authors) 6 refs.Google Scholar
- 1976–356.Lizzi, F., Katz, L., St. Louis, L. and Coleman, D. J., “Applications of Spectral Analysis in Medical Ultrasonography,” Ultrasonics, 77–80 (March 1976). “Spectral analysis of ultrasonic reflections from biological tissues can be used to determine basic tissue parameters for use in differential diagnosis. This paper describes the use of the technique under circumstances encountered in several types of clinical examinations. The applications are illustrated with results obtained from laboratory measurements with a system now being employed in a clinical evaluation programme. The test objects studied simulate tissues with planar boundaries, tissues with heterogeneous interior structure, and tissues causing acoustic ‘shadowing’ of posterior regions” (authors) 6 refs.Google Scholar
- 1975–357.Lele, P. P., Mansfield, A. B., Murphy, A. I., Namery, J., and Senapati, N., “Tissue Characterization by Ultrasonic Frequency-Dependent Attenuation and Scattering,” Proc. Sem. Ultrason. Tissue Charac., NBS Special Pub. 453. “Studies conducted in this laboratory to explore the feasibility of utilizing acoustic impedance, attenuation, and scattering characteristics of tissues for enhancing the diagnostic capabilities of ultrasound are described. Frequency-dependent ultrasonic attenuation is found to be sufficiently greater in infarcted or otherwise necrotized tissues than in normal controls to permit their positive identification. Superficial and internal scattering properties of tissues hold the promise of being significant for diagnostic applications. The difficulties that will have to be overcome to successfully utilize these properties are discussed” (authors) 24 refs.Google Scholar
- 1978–358.Serabian, S. and Williams, R. S., “Experimental Determination of Ultrasonic Attenuating Characteristics Using the Roney Generalized Theory,” Mat. Eval. 55–62 (July 1978). “To date, little use has been made of the generalized theory of ultrasonic attenuation in polycrystalline materials proposed by Roney. It is the only generalized theory which appears to run the gamut of grain size and frequency dependency of attenuation from the hysteresis loss mechanism through the complete scattering losses, i.e., Rayleigh, phase and diffusion. The theory requires only two constants—a hysteresis constant for the hysteresis losses and a scattering coefficient to describe those losses due to scattering. In the frequency range normally associated with the ultrasonic interrogation method the hysteresis losses are essentially negligible, thus, the scattering coefficient can fully describe the ability of a given material to propagate ultrasound. Moreover, this assessment of the material can be made without necessitating direct inferences to the grain size or frequency involved” (authors) 30 refs.Google Scholar
- 1973–359.Kesler, N. A., Merkulov, L. G., Shmurun, Y. A., and Tokarev, V. A., “Ultrasonic Spectral Method for Attenuation Measurement and Device for Automatic Testing of Microstructure of Materials,” Proc. 7th Int. Conf. on NDT, Session J-34 (Warszawa, 1973). This paper presents the mathematics and an experimental technique for determining the attenuation in a plane parallel plate, over a band of ultrasonic frequencies. 3 refs.Google Scholar
- 1974–360.Heyser, R. C. and Le Croissette, D. H., “A New Ultrasonic Imaging System Using Time Delay Spectrometry,” Ultrasound in Med. and Biol. 1, 119–131. “A new method of forming a visual image by ultrasound is described. A shadowgraphic transmission image similar to an x-ray radiograph is produced by the application of a technique known as Time Delay Spectrometry. The system uses a repetitive frequency sweep with a linear relationship between frequency and time and the transmitting and receiving crystal are scanned in raster fashion about the subject. By electronic processing, an image may be built up which represents the energy transmitted through the specimen with a given time delay. An intensity modulated picture encompassing the full shades-of-gray capability of the recording system can be produced. A second type of image showing transmission time through the specimen may also be formed. Brightness changes in the displayed image in this case correspond to changes in the ultrasonic transmission time through the specimen. There is no analog for this type of image in current x-ray or ultrasonic practice. Examples of both types of images of specimens both in vitro and in vivo are shown. The advantages and potentials of this method for biomedical ultrasonic imaging and analysis are discussed” (author) 6 refs.Google Scholar
- 1975–361.Alers, G. and Graham, L. J., “Reflection of Ultrasonic Waves by Thin Interfaces,” Proc. 1975 IEEE Ultrason. Symp., 579–582. “In order to measure the quality of an adhesive bond using ultrasonic waves, it is important to recognize those features in a reflected echo that carry information about the structure of the thin, chemically different interface between the adhesive and the adherend. We have studied the frequency dependence of the phase and amplitude of ultrasonic pulses reflected from very thin bonds formed between identical blocks of Lucite so that the reflection process is dominated by the nature of the interface and not by the impedance mismatch that occurs in practical adhesive to metal joints. The results show a frequency independent reflection coefficient over the range of 2.5 to 10 MHz which is very difficult to fit with currently available models of reflection from thin layers” (authors) 5 refs.Google Scholar
- 1971–362.Lees, S., “Ultrasonic Measurement of Thin Layers,” IEEE Trans. Son. Ultrason., SU-18 (2), 81–86. “The shape of a pulse echo from a thin layer embedded between two thicker media is changed because the successive echoes from the two close interfaces overlap. A simple computer algorithm is developed for real time computation of the change in shape as a function of the film thickness. It is only necessary to know the specific acoustic impedances of the three media. In one experiment castor oil was embedded between glass and steel. The calculated echoes closely resembled the experimental results for films between 1- and 38-μ thick. A curve was devised for estimating the film thickness from peak ratios in the echo. A second experimental situation appeared in testing acoustical transmission across an amalgam-tooth dentin boundary with water as the film medium. Numerical calculations produced the same echo patterns as were observed indicating that there is a gap in the interface between 1 and 10 μ in the samples” (author).Google Scholar
- 1978–363.Heyman, J. S., “Phase Insensitive Acoustoelectric Transducer,” J. Acoust. Soc. Am. 64 (1), 243. “Conventional ultrasonic transducers transform acoustic waves into electrical signals preserving phase and amplitude information. When the acoustic wavelength is significantly smaller than the transducer diameter, severe phase modulation of the electrical signal can occur. This results in anomalous attenuation measurements, background noise in Non-Destructive Evaluation (NDE), and in general complicates data interpretation. In this article, we describe and evaluate a phase insensitive transducer based on the acoustoelectric effect. Theory of operation of the Acousto-Electric Transducer (AET) is discussed and some optimization procedures outlined for its use. Directivity data for the AET is contrasted with a conventional piezoelectric transducer. In addition, transmission scanning data of phantom flaws in metal plates is presented for both transducers and demonstrates a significant improvement in resolution with the AET” (author).Google Scholar
- 1966–364.Carome, E. F., Moeller, C. E. and Clark, N. A., “Intense Ruby-Laser-Induced Acoustic Impulses in Liquids,” J. Acoust. Soc. Am. 40 (6), 1462. “An experimental study has been made of the acoustic signals induced in liquids by the focused beam from a Q-spoiled ruby laser. Very intense acoustic impulses have been produced with laser pulses of less than 0.05 J total energy. These appear to be generated by dielectric breakdown and not associated with the hypersonic waves that may be produced simultaneously by stimulated Brillouin scattering. The observed impulses have peak pressures of approximately 500 atm and frequency components in excess of 2400 Mc/sec.” (Authors), 8 refs.Google Scholar
- 1977–365.von Gutfield, R. J. and Melcher, R. L., “20 MHz Acoustic Waves from Pulsed Thermoelastic Expansions of Constrained Surfaces,” J. Acoust. Soc. Am. 30 (6), 257–259. “Repetitive pulses from lasers with pulse widths 5–10 nsec or a current generator with 10–25-nsec widths have been used to launch acoustic waves by thermoelastic expansions. For the laser case, when transparent media such as quartz plates are used to acoustically constrain the energy absorbing surface, an increase of up to 46 dB at 20 MHz was observed over that generated from a free surface. An experiment using a scannable laser to generate elastic waves for flaw detection in a metallic sample is described.” (Author), 5 refs.Google Scholar
- 1973–366.Thompson, D. O., editor of Proceedings of the Interdisciplinary Workshop on Nondestructive Testing — Materials Characterization, AFML-TR-73–69, April 1973. “The field of nondestructive testing and materials characterization is examined with emphasis on new approaches that may lead to significantly improved future capabilities. The presentations range from examples of present capabilities and limitations to field of basic research. The recommendations of four panels are presented for future research and development to advance the present state-of-the-art.” (Editor)Google Scholar
- 1975–367.Thompson, D. O., “Interdisciplinary Program for Quantitative Flaw Definition — Special Report First Year Effort,” ARPA/AFML Contract F33615–74-C-5180 This report contains summaries of work performed in: (1) Quantitative Flaw Definition - piezoelectric and electromagnetic transducers - data processing - theoretical and experimental work on scattering of ultrasound from defects - system integration - sample preparation (2) Bond Strength - acoustical interactions at thin interfaces - nature of bonded interface degradation in composites (3) Failure Prediction - determination of residual stresses in structural material - acoustic emission 1975–368 Lakin, K. M., “Piezoelectric Transducers,” Project I, Unit I, Task 1, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 8–16. Work is presented on transducer construction, transducer circuit modeling and the construction of a data acquisition system for use in radiation field pattern analysis. 2 refs.Google Scholar
- 1975–369.Maxfield, B. W., “Optimization and Application of Electrodynamic Acoustic Wave Transducers,” Project I, Unit I, Task 2, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 17–32. Electromagnetic acoustic wave transducers (EMATS) are analyzed theoretically. The acoustic field predicted is compared to that produced in an experimental system. 1 ref.Google Scholar
- 1975–370.White, R. M, and Kerber, G. L., “Analog Data Processing,” Project I, Unit II, Task 2, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 51–56. The rationale for deconvolution filtering is discussed. A system, utilizing a surface acoustic wave (SAW) filter, is presented. 1 ref.Google Scholar
- 1975–371.Yee, B. G. W., Couchman, J. C. and Bell, Jr., “Digital Techniques for Ultrasonic Flaw Characterization,” Project I, Unit II, Task 3, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 57–85. The hardware and software for these investigator’s data collection and signal processing system are described. Numerous timed and frequency domain signatures for spheroids and flat-bottomed holes were acquired— many are presented. Preliminary comparisons with theory are discussed.Google Scholar
- 1975–372.Adler, L., “Models for the Frequency Dependence of Ultrasonic Scattering from Real Flaws,” Project I, Unit III, Task 1, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 86–111. The author discusses a geometrical theory of diffraction for acoustic waves (based on the electromagnetic theory of Keller). The author’s experimental system for studying the angular and frequency dependence of acoustic wave scattering from defects is presented. Theory and experiment agree reasonably well, with excellent agreement as to the spacing of nulls in the spectra. 4 refs.Google Scholar
- 1975–373.Packman, P. F. and Coyne, E. J., “Defect Characterization by Spatial Distribution of Ultrasonic Scattered Energy,” Project I, Unit III, Task 2, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 112–127. “The ability of the ultrasonic indicia to characterize the shape and size of imbedded defects has been developed and examined.” (Author), 23 refs.Google Scholar
- 1975–374.Tittmann, B. R., “Comparison of Theory and Experiment for Ultrasonic Scattering from Spherical and Flat-Bottom Cavities,” Project I, Unit III, Task 3, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 128–139. The author compares his experimental measurements to the theory of Ermolov (solution of a scalar potential equation for normal incidence of longitudinal waves on a rigid, motionless disk in a fluid). Agreement is good considering the simplicity of Ermolov’s solution. 5 refs.Google Scholar
- 1975–375.Krumhansl, J. A., Gubernatis, J. E., Huberman, M., and Domany, E., “Theoretical Studies of Flaws and NDE,” Project I, Unit III, Task 4, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 140–144. “1. The general information of integral equation scattering theory for vector elastic waves has been reviewed and summarized in a report just being completed. While there is much literature (acoustic) for scalar wave problems, we believe this to be the first time that the details for elastic wave systems have been documented. Our writeup can serve as a source for this theory. 2. The first Born approximation to the general integral equation has been obtained both in analytic form, and programmed for computations. 3. For spherical flaws, the exact partial wave solutions in the literature (Truell et al.) have been checked [some algebraic corrections], programmed, and evaluated. 4. Thus, we have computed Born approximation and exact scattering, of incident longitudinal or transverse waves by spherical scatterers — as a function of scattering angle (0 – 180°) and for kr
_{s}from 0 to about 6. The cases considered are (a) spherical holes in Al, Ti, and stainless steel, and (b) Al and stainless steel spheres in aluminum. 5. The practically useful conclusion is that there are many useful regimes of the first Born approximation — which because of its relative simplicity does not require extensive computing effort for use. This shows promise as a first approximation to explore scattering pattern features (signatures).” (Authors)Google Scholar - 1975–376.Kraut, E. A., “Review of Theories of Scattering of Elastic Waves by Cracks,” Project I, Unit IV, Task 1, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 145–162. Scattering of elastic waves by a 2-dimensional crack of arbitrary shape in an unbounded elastic medium is considered. The Kirchhoff approximation is discussed, and the scattering from a penny-shaped crack is investigated. 44 refs.Google Scholar
- 1975–377.Alers, G. A. and Graham, L. J., “Ultrasonic Wave Interaction with Interfaces,” Project II, Unit I, Task 1, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 183–196. “Adhesive bonds of different mechanical strength, between identical materials, were fabricated by both chemical and thermal means.” (Author) The frequency dependence of the amplitude of ultrasonic signals from the bonds is experimentally determined and compared to theoretical models and to the bond strength. 5 refs.Google Scholar
- 1975–378.Rose, J. L. and Meyer, P. A., “Ultrasonic Signal Processing Methods for Adhesive Bond Strength Measurements,” Project II, Unit I, Task 2, in Interdis. Pgm. for Quant. Flaw Def. — Spec. Rpt. 1st Yr. Effort, 197–231. “The purpose of this work is to examine the effects of selected attenuation functions in adhesive bond modeling problems so that the attenuation in signal processing and interpretation can be treated adequately. Bond models are presently being used to study such problems as improper substrate surface preparation, improper adhesive cure, or chemical segregation of the adhesive. .,. . Results indicate that attenuation effects can substantially alter the ultrasonic reflection even though the bondline is relatively thin. ...” (Authors)Google Scholar
- 1974–379.Tittmann, B. R. and Cohen, E. R., “Acoustic Wave Scattering from a Sphere,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238, 173–186. “The objective of this program is to calculate the frequency and angular dependence of the ultrasonic energy scattered from a solid ellipsoid of revolution embedded in another solid. This calculation must take into account the mode conversion that takes place at the boundaries of the ellipsoid. The first phase will concentrate on the spherical case so that a simple ellipsoid can then be treated by perturbation methods. The vector and scalar potential problem for the sphere has been solved and is programmed onto the computer at the Science Center. In order to check this program, the case of a rigid, motionless sphere is being calculated because it can be compared to the results of a published calculation by Morse. An integral part of this program is an experimental check on the calculations performed by making accurate measurements of the angle and frequency dependence of the scattering of ultrasonic waves in the 1 to 15 MHz range. A 2–1/2 inch diameter by 2–1/2 inch thick sample containing a single spherical void 400 microns in diameter is being prepared by diffusion bonding techniques. Pure titanium has been chosen for the host material because it showed a minimum amount of attenuation and background scattering. Spheres of tungsten carbide and magnesium will also be embedded in other titanium samples so that a detailed study of mode conversion effects can be made.” (Author) 3 refs.Google Scholar
- 1974–380.Mucciardi, A. N., “Adaptive Nonlinear Modeling for Ultrasonic Signal Processing,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238, 194–212. “... The main objectives of this project are to evaluate the efficacy of adaptive nonlinear signal processing techniques to model material flaw descriptors with high accuracy. This modeling synthesis procedure has its expression in a nonlinear adaptive trainable network. The procedure is unique because a detailed knowledge of the underlying physical phenomena is not required. Indeed, it is believed that such information is contained implicitly in the experimental data, and it is the purpose of the methodology to extract this information and to generate models accordingly. ... In this current project, the feasibility of adaptive nonlinear signal processing techniques for UNDT will be demonstrated. In particular, adaptive trainable networks will be synthesized for characterization of UNDT waveforms for accurate inferences of: (1) flat-bottom-hole sizes, and (2) the length of fatigue cracks. . . . These results will provide important information to metallurgical investigators regarding the relationships between the best-found UNDT waveform parameter subsets and the underlying physical phenomena.” (Author)Google Scholar
- 1974–381.Moran, T. J., “Studies of Electromagnetic Sound Generation for NDE,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238, 213–223. “The technique of electromagnetic sound generation has been known since 1967. Since it provides a contactless means of generating ultrasonic waves in metals, application of the technique to NDE would eliminate the problem of coupling the transducer to the sample under evaluation. It is also an extremely flexible technique since it can be used to generate bulk and surface waves of all polarizations. At its present state of development, the technique is relatively inefficient in converting RF energy to sound energy in comparison to standard transducer techniques and it is also material dependent since the generation of the sound occurs inside the material near the surface. The goal of the present work is to first optimize the efficiency of the generation process and secondly, to perform a systematic study of the generation efficiency in many materials of present interest in manufacturing. We will use both unflawed samples and those with well-characterized flaws to determine the detection capabilities.” (Author), 4 refs.Google Scholar
- 1974–382.Felix, M. P., “Laser-Generated Ultrasonic Beams,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238, 224–240. “A device has been developed which uses a Q-switched laser pulse to produce a plane compressive stress pulse or a slowly decaying sinusoidal stress wave train in any solid or liquid material. The device utilizes a thin liquid layer to totally absorb the laser pulse and generate a stress pulse by rapid thermal expansion. Compressive stress pulses of 200 nanosecond duration and up to 5 kilobars amplitude have been obtained. Wave trains of about 30 cycle duration and 1/4 kilobar amplitude (peak-to-peak in typical solids) have been obtained at frequencies between 1–25 MHz. Stress amplitudes may be varied by filtering the incident laser radiation. This device should prove useful wherever large amplitude stress pulses or large amplitude sinusoidal wave trains are required—such as in nondestructive testing.” (Author)Google Scholar
- 1974–383.Meyer, P., “Ultrasonic Procedures for Predicting Adhesive Bond Strength,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238; 340–351. “Theoretical wave propagation models that treat ultrasonic wave interaction with an adhesively bonded system have been developed. These models allow the selection of appropriate ultrasonic transducers for bond inspection analysis. Such problems as a variation in bondline thickness, the presence of density gradients in the adhesive bond and improper surface preparation are treated in detail. Preliminary results indicate that the potential for success appears quite high for obtaining a correlation between a bond performance parameter and some specific ultrasonic test parameter.” (Author)Google Scholar
- 1974–384.Yee, B. G. W., “Applicability of Ultrasonic Resonance Spectroscopy to NDE of Adhesive Bonds,” Proc. Interdis. Workshop for Quant. Flaw Def., Tech. Rpt. AFML-TR-74–238, 352–371. “Work being done at General Dynamics involving computerized signal processing of ultrasonic wave forms from metals, laminates and composites is discussed. The method has application for materials characterization and defect detection. A Hewlett-Packard 2100A digital computer was included into a laboratory tool for the signal processing described. The signal processing system includes an ultrasonic puiser, broad-band piezoelectric transducer, stepless gate oscilloscope, display scanner, and computer interface converter channels. Digitized wave forms are filtered and Fourier transformed by computer sof-ware and then displayed on an X-Y grid. A detailed description of wave-form digitization Fourier transforms, signal convolution and interpretation of results will be presented. The applicability of the computerized scheme to crack width detection, acoustic impedance determination, partial bond characterization and sound velocity measurements will be discussed. The prospective use for measuring the strength of bonded materials will also be discussed.” (Author)Google Scholar
- 1975–385.Cohen, E. R., “Analysis of Ultrasonic Scattering from Simply Shaped Objects,” Proc. of the ARPA/AFML Review of Quant. NDE, AFML-TR-75–212, 47–55. The mathematics of acoustic wave scattering from spheres and spheroids is developed.Google Scholar
- 1975–386.Krumhansl, J. A., “Basic Theory of Ultrasonic Scattering by Defects: Numerical Studies and Features for Experimental Application,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 57–66. The author summarizes his theoretical work on scattering of ultrasound by defects. An integral equation governing the scattering by an arbitrary shaped flaw is used. 3 refs.Google Scholar
- 1975–387.Packman, P. F. and Coyne, E. J., “Defect Characterization by Spatial Distribution of Ultrasonic Scattered Energy,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 129–146. Essentially the same as (1975–373).Google Scholar
- 1975–388.Sachse, W., “Scattering of Ultrasonic Pulses from Cylindrical Inclusions in Elastic Solids,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 147–168. A data collection and analysis system is presented. The angular and frequency-dependent scattering from imbedded cylinders is studied. The author performs the important task of identifying the received signals with the probable ray paths of the ultrasound. 8 refs.Google Scholar
- 1975–389.Couchman, J., “Digital Measurements of Scattering from Spheroids and Flat-Bottom Holes,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 169–194. Essentially the same as (1975–371).Google Scholar
- 1975–390.Tittmann, B., “Comparison of Theory and Experiment for Ultrasonic Scattering from Spherical and Flat Bottom Cavities,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 195–217. Essentially the same as (1975–374).Google Scholar
- 1975–391.Adler, L., “Angular Dependence of Ultrasonic Waves Scattered from Flat Bottom Holes,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 219–245. Essentially the same as (1975–372).Google Scholar
- 1975–392.White, R., “Surface Acoustic Wave Filters for Real Time Processing of Ultrasonic Signals,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 321–341. An expanded version of (1975–370). A clearly written and detailed explanation of how a SAW filter may be used for deconvolution.Google Scholar
- 1975–393.Mucciardi, A. N., “Adaptive Learning Network Approach to Defect Characterization,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 363–383. The feasibility of employing pattern recognition techniques to ultrasonic NDE is assessed. A data collection system is described and an adaptive learning network (ALN) is presented. The ALN flat-bottom hole classifier is found to be extremely accurate, 20 refs.Google Scholar
- 1975–394.Forsen, G., “Interactive Pattern Analysis and Recognition,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 385–398. The general approach of applying pattern analysis and recognition to NDE is discussed. 2 refs.Google Scholar
- 1975–395.Maxfield, B., “Optimization and Application of Electrodynamic Ultrasonic Wave Transducers,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 399–412. Essentially the same as (1975–369).Google Scholar
- 1975–396.Thomas, R., “Acoustic Surface Wave Generation with Electromagnetic Transducers,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 413–428. The author has extended the technique of EMAT-generated surface waves to frequencies in the MHz range (typically 4.5–10 MHz). The possibility of extending the range to 40 MHz seems to be good if the coil can be placed near enough to the sample surface.Google Scholar
- 1975–397.Frost, H. M. and Szabo, T. L., “Transducers Applied to Measurements of Velocity Dispersion of Acoustic Surface Waves,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 429–450. Wedge transducers, comb transducers, and flat cable and hand wound EMATS were used to measure surface wave dispersion. Results of the experiments are presented. 2 refs.Google Scholar
- 1975–398.Lakin, K., “Piezoelectric Transducers for Quantitative NDE,” Proc. ARPA/AFML Rev. of Quant. NDE,” AFML-TR-75–212, 463–478. A somewhat expanded version of (1975–368).Google Scholar
- 1975–399.Alers, G. and Graham, L., “Ultrasonic Wave Interactions with Interfaces,” Proc. ARPA/AFML Rev. Quant. NDE, AFML-TR-75–212, 579–593. Essentially the same as (1975–377).Google Scholar
- 1975–400.Rose, J., “Attenuation Influences in Adhesive Bond Modeling,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 595–611. Essentially the same as (1975–378).Google Scholar
- 1975–401.Seydel, J. A., “Methods Development for Nondestructive Measurement of Bond Strength in Adhesively Bonded Structures,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 613–630. The author uses an equivalent-time sampling and digitization system to acquire pulse-echo data from adhesive bonds. Attempts are made to characterize adhesive bond strength by a measurement of ultrasonic reflectivity as a function of frequency. 8 refs.Google Scholar
- 1975–402.Szabo, T., “Residual Stress Measurements from Surface Wave Velocity Dispersion,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 749–767. A method of inferring a subsurface residual stress gradient from surface wave dispersion data is presented. The techniques involve an inverse Laplace transformation of normalized dispersion data. 5 refs.Google Scholar
- 1975–403.Richardson, J., “Deducing Subsurface Property Gradients from Surface Wave Dispersion Data,” Proc. ARPA/AFML Rev. of Quant. NDE, AFML-TR-75–212, 769–790. Two situations are analyzed: (1) the dense data case, in which dispersion data are assumed to be available for all wavelengths, and (2) the sparse data case. An estimation theory approach is used to give the most probable subsurface gradient.Google Scholar
- 1976–404.Ulrych, T. J. and Clayton, R. W., “Time Series Modelling and Maximum Entropy,” Physics of the Earth and Planetary Interiors 12, (2/3), 188–200. “This paper briefly reviews the principles of maximum entropy spectral analysis and the closely related problem of autoregressive time series modelling. The important aspect of model identification is discussed with particular emphasis on the representation of harmonic processes with noise in terms of autoregressive moving-average models. It is shown that this representation leads to a spectral estimator proposed by Pisarenko in 1973.” (Author), 35 refs.Google Scholar
- 1976–405.Thompson, D. O., editor of Interdisciplinary Program for Quantitative Flaw Definition-Special Report Second Year Effort, Report for ARPA/ AFML under Contract F33615–74-C-5180. “The technical results of the second year of effort sponsored by the ARPA/AFML Center for Advanced NDE . . . are assembled in this report. They are grouped into three projects . . . (1) Flaw Characterization by Ultrasonic Techniques - electromagnetic transducers - characterization of NDE transducers - signal processing with SAW devices - high frequency ultrasonics - adaptive learning - sample preparation - fundamental scattering studies – standards - flaw detection in ceramics (2) Measurement of Strength Related Properties - adhesive bond strength - strength of composites (3) Nondestructive Measurement of Residual Stress in Metals - inference from harmonic generation - inference from efficiency of the electromagnetic generation of ultrasound . . .” (Editor).Google Scholar
- 1976–406.Thompson, R. B. and Fortunko, C. M., “Optimization of Electromagnetic Transducer Systems,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 1–19. The electronics and coil designs are optimized to provide the maximum signal to noise ratio. 13 refs.Google Scholar
- 1976–407.Lakin, K. M., “Characterization of NDE Transducers,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 30–43. Field pattern measurements are made utilizing the system described in previous publications. S-parameters are introduced as a “convenient means of describing devices involving transmission line type behavior.” 11 refs.Google Scholar
- 1976–408.White, R. M., “Signal Processing with SAW Devices,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 44–99. An update on the author’s work with SAW inverse filters.Google Scholar
- 1976–409.Elsley, R. K., “Quantitative Estimation of Properties of Ultrasonic Scatterers,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 63–86. The author describes how a data base of theoretical and ultrasonic scattering results was assembled. The data are to be used to train on adaptive learning network. “Some efforts were also directed toward investigating simple, non-adaptive learning techniques for inferring at least the size of the scattering object from the scattering data.” 2 refs.Google Scholar
- 1976–410.Mucciardi, A. N., “Application of Adaptive Learning Networks to NDE Methods,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr, Effort, 87–88. Describes the objectives of a project to model flaw characteristics obtained from theoretical ultrasonic scattering waveforms via adaptive learning decision algorithms.Google Scholar
- 1976–411.Krumhansl, J. A., “Theoretical Studies of Ultrasonic Scattering and Defects,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 102–122. The regions of applicability and validity of the Born approximation are determined. Other approximations (static, quasistatic) are evaluated. Work on scattering from flat cracks is detailed. 6 refs.Google Scholar
- 1976–412.Tittmann, B. R., “Measurements of Scattering of Ultrasound by Ellipsoidal Cavities,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 123–139. Scattering from ellipsoidal cavities is experimentally investigated. A contact method is utilized with the cavity at the center of a “doorknob” shaped sample. Incident longitudinal and shear waves are used. 1 ref.Google Scholar
- 1976–413.Adler, L. and Lewis, D. K., “Models for the Frequency Dependence of Ultrasonic Scattering from Real Flaws,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 140–166. “Scattering of elastic waves at flaws embedded in titanium was analyzed by measuring frequency and angular dependence of the scattered intensity pattern. This scattered intensity pattern was also calculated from two existing theories: (1) Keller’s geometrical theory of diffraction, which was solved for two-dimensional, crack-like flaws of circular and elliptical symmetries; (2) “Born approximation,” a scattering theory (introduced by Krumhansl et al., Cornell) for the spherical oblate and prolate spheroidal cavities. The experimental result was favorable compared to theory.” (Authors)Google Scholar
- 1976–414.Evans, A. G., Tittmann, B. R., Kino, G. S., and Khuri-Yakub, P. T., “Ultrasonic Flaw Detection in Ceramics,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 177–209. A high frequency (200 MHz) ultrasonic system is described. Techniques for accurate attenuation measurements have been made. Microstructure and scattering from defects have been studied. 7 refs.Google Scholar
- 1976–415.Alers, G. A. and Thompson, R. B., “Trapped Acoustic Modes for Adhesive Strength Determination,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 215–237. “The experiments discussed in this report were designed to consider the case in which the acoustic energy propagates parallel to the metal adhesive interface (of an adhesive bond) so that small differences in the boundary conditions could accumulate over a large interaction distance.” (Author), 6 refs.Google Scholar
- 1976–416.Flynn, P. L., “Cohesive Strength Prediction of Adhesive Joints,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 238–263. “An analytical study has been carried out to derive the acoustic spectral response of an attenuating adhesive bondline in terms of the physical properties of the adhesive . . . Experimental verification of the derived correlations was provided by systematically varying the properties of Chemlok 304, . . . correlated well Vith the ultrasonic amplitude ratio, sound velocity, attenuation coefficient and resonance depth. Correlation was not evident between resonance quality and strength because the sound velocity and attenuation of the adhesive were inversely related.” (Author), 6 refs.Google Scholar
- 1976–417.Rose, J. L. and Thomas, G. H., “Ultrasonic Attenuation Effects Associated with the Metal to Composite Adhesive Bond Problem,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 2nd Yr. Effort, 321–342. “Two different composite modeling approaches were used in this study. The first considered a 5-layer composite with the interfacial reflection caused by a very thin epoxy layer between composite layers. The second model consisted of an area discontinuity factor between each composite layer that accounted for the reflection factor at the interface. . . . The effect of composite masking was not significant in the 0–7 MHz range. After 7 MHz, however, the composite masking begins to show some significant effects, the effects however still being separable from the surface preparation or bond quality information.” (Author), 5 refs.Google Scholar
- 1977–418.Thompson, D. O., editor of Interdisciplinary Program for Quantitative Flaw Definition-Special Report Third Year Effort, Report for ARPA/AFML under Contract F33615–74-C-5180. “This report presents technical summaries of the various research tasks that have been pursued in the third year of effort by the ARPA/AFML Center for Advanced NDE. . . . They are grouped into two projects: (1) Flaw Characterization by Ultrasonic Techniques - electromagnetic and piezoelectric transducers - signal processing (SAW and CCD) - sample preparation - fundamental scattering studies (experimental and theoretical) imaging - adaptive learning - inversion techniques - failure prediction in ceramics - detection and characterization of surface flaws (2) Measurement of Strength Related Properties - adhesively bonded materials - composite materials - residual stress”Google Scholar
- 1977–419.Lakin, K. M. and Strand, T., “Characterization of NDE Transducers,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 21–41. “The problem of characterizing NDE transducers has been approached from two directions. First, the radiation pattern of the transducer has been analyzed in terms of Fourier transform reconstructions that yield information about the magnitude and phase of the fields anywhere in the region beyond the very near field. . . . The program (also) resulted in a simple but concise method for modelling the transducers as two-part hybrid networks ...” (Authors), 10 refs.Google Scholar
- 1977–420.White, R. M., “Signal Processing Research in Connection with Ultrasonics in Non-Destructive Testing,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 43–58. An analog data acquisition is described using a change coupled device (CCD) video delay line. A fast clock is used during acquisition; a slow clock for readout. Also a CCD transversal filter is used for matched filtering.Google Scholar
- 1977–421.Krumhansl, J. A., “Development and Application of Ultrasonic Scattering Theory to Non-Destructive Evaluation—Three Year Summary,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 64–69. A summary of the following work is presented. “(a) Careful examination of the general long wave limit in order to determine the maximum number of independent defect parameters which can be determined from scattering data. (b) Long wave and high frequency limits of scattering by cracks. (The Born approximation is not well defined for cracks.) (c) Addressing the ‘inverse’ problem. (d) Attempts to obtain an ‘exact’ (calibration) scattering solution for a few spheroidal geometries, to complete evaluation of Born approximation errors.” (Author), 19 refs.Google Scholar
- 1977–422.Domany, E., “Utilization of Physical Features of Scattered Power for Defect Characterization,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 70–81. “The first Born approximation provides a useful means to study scattering of ultrasound by various defects. In particular, it seems to yield qualitatively good results for the scattered power when averaged over a range of frequencies. Features of the scattered power that have been discovered by this method are reviewed. A convenient way to summarize the scattering data, by numerical projections, was used to assemble a library of scattered power from various defects. Addressing the particular problem of an oblate spheroidal cavity, a step-by-step procedure to determine its orientation and shape is suggested. Areas of future development are indicated.” (Author), 10 refs.Google Scholar
- 1977–423.Tittmann, B. R., Elsley, R. K., Nadler, H., and Cohen, E. R., “Experimental Measurements and Interpretation of Ultrasonic Scattering by Flaws,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 82–121. “The objective of this investigation was to develop procedures for deducing key geometric features of flaws from the details of the ultrasonic scattered fields, and, in particular, those features necessary for the evaluation against quantitative accept/reject criteria derived from fracture mechanics. To accomplish this objective, the investigation sought to correlate flaw characteristics such as size, shape, orientation and content of the flaw with the absolute value of scattered power and its variation with scattering angle and ultrasonic frequency, to verify theoretical scattering models developed by Krumhansl et al. (this report), and to lay the basis for inversion procedures developed by Mucciardi (see this report) and Bleistein (see this report).” (Author), 14 refs. (“This report” refers to Ref. 418.)Google Scholar
- 1977–424.Adler, L., “Identification of Flaws from Scattered Ultrasonic Fields as Measured at a Planar Surface,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 122–158. “The objective of this investigation was to correlate ultrasonic scattering data—such as the variation of scattered power with angle and frequency, mode conversion, etc.—to characteristics of a flaw in solids such as size, shape, and orientation by using flat samples and an immersed system.” (Author), 10 refs.Google Scholar
- 1977–425.Kino, G. S., “New Techniques for Acoustic Nondestructive Testing,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 159–175. A phased array imaging system is described. The circuitry and inverse filter system are useful to anyone constructing an ultrasonic system (quantitative or imaging).Google Scholar
- 1977–426.Mucciardi, A. N., Shankar, R., Shaley, M. F., and Johnson, M. D., “Application of Adaptive Learning Networks to NDE Methods,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 176–231. Adaptive learning networks to the following problems. - measurement of the size and acoustic impedance of spherical defects from the analysis of theoretically scattered waveforms. - actual scattering from spherical defects. - estimate the size and orientation of spheroidal defects from analysis of the Born approximation model. 6 refs.Google Scholar
- 1977–427.Bleistein, N. and Cohen, J., “Application of a New Inverse Method for Nondestructive Evaluation,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 232–246. “The application of a new inverse method to nondestructive evaluation is described. In particular, detection of a small hole in an otherwise homogeneous solid is discussed. The scattering of an acoustic probe by the hole is considered. It is shown that the scattered wave is proportional to the Fourier transform of the characteristic function of the domain occupied by the hole. The characteristic function is equal to unity in that domain and zero outside. Thus, knowledge of this function characterizes the domain. The basic result is derived under the assumption that the scatterer is small — allowing use of the Born approximation — and “far” from the surface of the solid. Some features of aperture limited — band limited and aspect angle limited — observations are discussed. The applicability of this inverse method to non-destructive evaluation is demonstrated by this preliminary analysis.” (Authors), 12 refs.Google Scholar
- 1977–428.Kino, G. S., Khuri-Yakub, B. T., Tittmann, B. R., Ahlberg, L., Evans, A. G., Biswas, R., and Fulrath, R., “Ultrasonic Failure Prediction in Ceramics,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 247–266. Defect characterization in the size range (10–100 micrometer) in structural ceramics was performed. High frequency techniques (200 MHz) were employed. A new ultrasonic technology, based on ZnO was developed as part of the problem. 8 refs.Google Scholar
- 1977–429.Alers, G. A. and Elsley, R. K., “NDE Techniques for Measuring the Strength of Adhesion,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort,” 271–285. “It has been the objective of this study to find ultrasonic techniques that can give a quantitative measure of the status of the metal to adhesive interface so that the adhesion strength of an adhesive bond could be predicted. ... it is possible to predict the approximate strength of the adhesive bond from a measurement of the splitting of the lowest standing wave resonance in the adherends.” (Authors), 7 refs.Google Scholar
- 1977–430.Flynn, P. L. and Henslee, S. P., “Cohesive Bond Strength Prediction, FM-400 a Realistic Adhesive System,” Interdis. Pgm. for Quant. Flaw Def.-Spec. Rpt. 3rd Yr. Effort, 286–307. “... Scattering analysis was applied to an adhesive layer and provided a basis for choosing measureable ultrasonic parameters that characterized the acoustic properties of the layer. This method was applied to simple adhesive systems with good results, but found some problems in general application. The largest problem in the scrimmed adhesive was entrapment of small voids in the scrim pattern. The small voids affected the attenuation measurements, but did not affect the cohesive strengths.” (Authors), 8 refs.Google Scholar
- 1977–431.Thompson, D. O., Proceedings of the ARPA/AFML Review of Progress in Quantitative NDE, Tech. Rpt. AFML-TR-77–44. These edited transcripts contain information relating to quantitative NDE. Included are summaries of work on: Adhesives and composites New materials and techniques Measurement of internal stress Fundamentals of acoustic emission Signal acquisition and processing Defect characterization - fundamentals (experimental and theoretical) and techniques. “In addition a Mini-Symposium is presented related to Advances in Electromagnetic Transducers.” (Editor)Google Scholar
- 1977–432.Alers, G. A., “Trapped Acoustic Modes for Adhesive Strength Determination,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 52–58. “In order to extend the time and distance over which an ultrasonic wave can interact with the strength determining layer at a metal to adhesive interface, we have considered the acoustic wave modes that propagate parallel to the interface in the plane of a sandwich type adhesive bond between two metal plates. A detailed mathematical analysis of these bound modes was made with special attention to the role played by the boundary conditions at the adhesive to metal interface so that the frequencies and modes that are most sensitive to the bounding conditions could be predicted. Experiments to verify these predictions were carried out using surface waves launched into the adhesive layer from the external metal plates and by current carrying wires embedded in the adhesive subjected to an external, static magnetic field. The theoretical analysis also predicted that the fundamental thickness mode of vibration of the entire sandwich structure should also exhibit a sensitivity to the boundary conditions. This was studied experimentally by taking the Fourier transform of low frequency echos reflected from the structure.” (Author)Google Scholar
- 1977–433.Flynn, P. L., “Cohesive Strength Prediction of Adhesive Joints,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 59–65. “An analytical study was carried out to determine the influence of changes in bondline properties on measurable ultrasonic parameters in both the time and frequency domains. An experimental study was conducted in which the adhesive properties were varied by mixing a paste adhesive in different ratios of resin and hardener. The properties of the adhesive bondlines were measured in-situ with high frequency, broad-band ultrasonics. Physical properties extracted from the ultrasonic data included the sound velocity, acoustic impedance and the attenuation of the adhesive layer. The expected correlations were seen between the NDE parameters identified by the analytical study and the strength and stiffness of the bonded specimens.” (Author), 3 refs.Google Scholar
- 1977–434.Buckley, M. J. and Raney, J. M., “The Use of Continuous Wave Ultrasonic Spectroscopy for Adhesive-Bond Evaluation,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 66–73. “For certain NDE applications, the use of CW ultrasonic spectroscopy to acquire ultrasonic transmission and reflection data has several advantages over pulse techniques. The specific system currently used to record amplitude and phase as a function of frequency over the range of 20 KHz to 20 MHz will be discussed. In addition, theoretical calculations of the ultrasonic spectra for adhesively bonded structures will be presented along with initial results obtained in fitting the theoretical calculations to the experimental data in order to determine the acoustic properties of the adhesive layer.” (Author), 2 refs.Google Scholar
- 1977–435.Evans, A. G., “Ultrasonic Flaw Detection in Ceramics,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 74–77. “A high frequency ultrasonic approach for determining defects in ceramic materials (in the size range required for failure prediction) has been outlined. A 200 MHz A-scan device pulsed with a short (2 ns) pulse has been constructed and shown to have a good dynamic range (70 dB) and a depth resolution of at least 25 microm. A B-scan system for defect detection studies has also been developed and is ready for use. Techniques for accurate attenuation measurements in ceramics have been developed and automated. Preliminary data have also been obtained on a range of ceramic polycrystals. Calculations of the scattering from defects in ceramics, and of bond losses in thin gold foils, have been used in cylinders with the attenuation data to predict typical defect detectabilities. These calculations predict that defects in the size range 20–100 microm. should be detectable (with the present transducers) in fully-dense, fine-grained ceramics. Preliminary defect detection studies have confirmed that defects at least as small as 100 microm. are readily detectable in these materials.” (Authors)Google Scholar
- 1977–436.Lakin, K. M., “Characterization of NDE Transducers,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 116–122. “A system for characterizing NDE transducers has been implemented which involves both electrical circuit modeling and measurements of the amplitude and phase of the radiation patterns. The field pattern measurements allow a determination of the field at the transducer surface as well as at locations distant from the transducer. The technique is also adaptable to characterizing scattering surfaces treated as apparent sources. The electrical characterization centers around a network model involving a hybrid set of S-parameters. Using simple and readily available references, the four parameters of the transducer may be determined and then used to quantitively predict the transducer performance in scattering experiments. In its simplest form the technique uses water bath experiments and scattering off the transducer surface.” (Author)Google Scholar
- 1977–437.Szabo, T. L., “Surface Acoustic V/ave Electromagnetic Transducer Modeling and Design for NDE Applications,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 128–132. “Recent progress in SAW electromagnetic transducer (EMT) modeling and fabrication techniques have greatly increased EMT versatility for NDE applications. Unlike other types of SAW NDE transducers that suffer from variability in manufacture and coupling conditions, virtually identical EMT1s can be made that have predictable characteristics. During the past year we have developed a new equivalent circuit model for the noncontact EMT that describes both its acoustical and electrical characteristics. This model is useful for design and for assessing the effects of electrical matching and transduction on different materials. Perhaps the most striking result of the model is the similarity in frequency response between the meander line SAW EMT and the SAW interdigital transducer. For conventional EMT’s, design is simple and in excellent agreement with experiment. By modification of transducer geometry, as with IDT’s, more advanced frequency response shapes can be realized. This result implies that for SAW EMT’s signal processing functions can be combined with transduction for NDE applications.” (Author), 10 refs.Google Scholar
- 1977–438.Maxfield, B. W., “Optimization and Application of Electrodynamic Acoustic Wave Transducers,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 133–135. “We have used electromagnetic acoustic-wave transducers (EMATs) to measure the intensity distribution of shear ultrasonic waves scattered by a cylindrical flaw and a conventional flat-bottomed hole. Results are in reasonable qualitative agreement with the behavior expected for these scattering arrangements. Quantitative measurements, however, have proven very difficult to obtain because of fundamental problems in providing adequate shielding for the receiver coil while avoiding distortion of the drive field. Our experimental work has defined the problem areas and in most cases suggested solutions. It now seems quite probable that other work, both in this program and outside, may yield definitive solutions to the problems that we have identified so that in the near future it may be possible to have quantitative shear wave scattering information from scanned EMAT measurements.” (Author)Google Scholar
- 1977–439.Moran, J. J., “Characteristics and Applications of Electromagnetic Surface Wave Transducers,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 136–141. “The steerability and relative generation efficiency of bulk acoustic waves generated by a meander line EMAT in aluminum have been determined. The frequency dependence of the propagation angle relative to the surface was found to agree well with theory. Efficiency for shear-wave generation (frequency range, 5–9 MHz) was about 4 dB per conversion less than the Rayleigh-wave generation efficiency at 4.6 MHz, and for longitudinal waves (frequency range, 10–24 MHz) about 10 dB less. A second effort to achieve piezoelectric SAW device signal processing capabilities with EMAT designs has shown that a pulse compression device is completely feasible. We have demonstrated that it is possible to compress a 3.5 ysec (2–6 MHz) chirp signal to a 0.25 ysec pulse. Possible applications will be discussed.” (Author)Google Scholar
- 1977–440.Thompson, R. B. and Fortunko, C. M., “Optimization of Electromagnetic Transducer Systems,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-44, 142–147. “The results of a program to realize maximum dynamic ranges with lightweight electromagnetic transducers suitable for hand-held use is described. Transducers were constructed using compact samarium-cobalt permanent magnets and: (1) spiral coils for generating axially polarized shear waves, (2) masked coils for generating plane polarized shear waves, and (3) meander coils for generating surface waves. A high power, line generator was constructed which uses a spark-gap to switch currents of several hundred amperes in either single pulse or tone burst mode of operation. A new transformer coupling network and a broadband, low noise preamplifier have been demonstrated for an overall 30 dB increase in sensitivity. Dynamic ranges as high as 80 dB were obtained in the tone burst mode (Δf/f ~ 10%). Applications of these transducers to problems of the Army and EPRI will be briefly discussed.” (Author), 7 refs.Google Scholar
- 1977–441.White, R. M., “Signal Processing with Surface Acoustic Wave Devices,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 148–153. “A surface acoustic wave (SAW) filter was designed and constructed having a response inverse to that of a simulated NDT system. Further testing of this filter was undertaken with the aim of characterizing the filter more accurately. A redesign of the filter to include an input transducer having less loss was then carried out. It appears that the use of a two-pair of three-pair input IDT is advantageous, and a filter incorporating such a transducer is now being fabricated for use with the simulated NDT system (5 MHz PZT transducer cemented onto an aluminum block). With this filter, determination is to be made of all the relevant electrical characteristics, as well as determination of the minimum spatial resolution obtainable at the filter output when two closely-spaced impedance discontinuities produce reflection.” (Author), 3 refs.Google Scholar
- 1978–442.Haines, N. F., Bell, J. C, and Mclntyre, P. J., “The Application of Broadband Ultrasonic Spectroscopy to the Study of Layered Media,” J. Acoust. Soc., Am. 64 (6), 1645–1663. “An investigation has been made of the frequency dependence of amplitude and phase information when broadband ultrasonic pulses, in the region 1–30 MHz, are reflected from layered targets. An on line computer performing Fourier analysis of sampled ultrasonic pulses allowed both amplitude and phase information to be studied. Layers of various acoustic impedances, velocities, and attenuation have been investigated, and in particular, layers of magnetite grown on mild steel. In all cases excellent agreement between experiment and theory has been achieved. The possible use of the techniques of deconvolution has also been considered for the measurement of the thickness of layers. The methods developed have found application in the problem of determining the thickness of a corrosion layer on the inside surface of a component where access can only be gained through the outer surface.” (Authors), 64 refs.Google Scholar
- 1977–443.Heyman, J., “A Non-Phase Sensitive Transducer for Ultrasonics,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 154–156. The phase-insensitive nature of a CsS acoustoelectric converter is discussed for applications in NDE.Google Scholar
- 1977–444.Krumhansl, J. A., “Interpretation of Ultrasonic Scattering Measurements by Various Flaws from Theoretical Studies,” Proc. ARPA.AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 164–172. “From a review and extension of the general theory of ultrasonic scattering by defects in elastic media we have developed computer programs and approximation methods for analyzing experimental scattering data. Few exact theoretical expressions are available, but significant information can be obtained from the “Born approximation,” the quasi-static approximation, and the exact long wave limit. Computed results for spheres and spheroids (prolate and oblate), for both longitudinal and transverse incident and scattered waves will be presented. In addition, we explore several methods for visual and graphical presentation of the analytical results for most convenient use in test situations.” (Author), 6 refs.Google Scholar
- 1977–445.Tittmann, B. R., “Scattering of Ultrasound by Ellipsoidal Cavities,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 173–179. “Experimental results have been compared with theory for ellipsoidal and spherical cavities embedded in titanium alloy by the diffusion bonding process. The measurements comprised the cases of incident longitudinal and shear waves including mode conversion. Whenever possible, comparisons were performed with the results of exact theory and those of the Born approximation. The Born approximation was found useful in the back scattering directions for low ka values (k is the wave vector of the sound wave and a is the radius of the scatterer). In the experiments, a reciprocity relation was discovered which should prove very useful in further studies: The same angular dependence is obtained in mode conversion when the mode of the incident and scattered wave is interchanged. This result has now been corroborated by both the exact theory and the Born approximation. The results are discussed in the context of failure prediction.” (Author), 4 refs.Google Scholar
- 1977–446.Adler, L. and Lewis, K., “Models for the Frequency Dependence of Ultrasonic Scattering from Real Flaws,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 180–186. “Scattering of elastic waves at flaws embedded in titanium was analyzed by measuring frequency and angular dependence of the scattered intensity pattern. This scattered intensity pattern was also calculated from two existing theories: (1) Keller’s geometrical theory of diffraction, which was solved for two-dimensional crack-like flaws of circular and elliptical symmetries; (2) “Born approximation,” a scattering theory (introduced by Krumhansl et al., Cornell) for the spherical oblate and prolate spheroidal cavities. The experimental result was favorably compared to theory.” (Authors)Google Scholar
- 1977–447.Mucciardi, A. N., “Measurement of Subsurface Fatigue Crack Size Using Nonlinear Adaptive Learning,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 194–199. “A new NDE nonlinear signal processing system has been developed to detect and measure small, subsurface fatigue cracks. The system synthesized from nondestructive evaluation (NDE) waveform parameter inputs is capable of detecting and measuring quantitatively subsurface fatigue cracks in the size range of 0 to 279 mils to within 70 percent of their nominally characterized lengths. Previous investigations had achieved a 50 percent detection rate for cracks larger than 30 mils. However, the fatigue crack measurement system reported herein is the first known fatigue crack NDE system capable of detection and measurement for this wide range.” (Author)Google Scholar
- 1977–448.Rose, J. L., Eisenstein, B., Fehlauer, J., and Avioli, M., “Defect Characterization—Fundamental Flaw Classification Solution Potential,” Proc. ARPA/AFML Rev. Prog. Quant. NDE, AFML-TR-77–44, 200–207. “Emphasis in the paper will be placed on a work description and analysis associated with a flaw classification problem of discriminating between ultrasonic signals that have been reflected from elliptical and circular side drilled electro discharge machined slots in a steel block. The flaw types used in this experiment are several elliptical holes with eccentricities, from .15 to 1.0. The signals are sampled at a 100 MHz rate and quantized with an 8 bit word length. The signal processing is performed on a PDP 11/05 mini-computer. . . . Results obtained thus far indicate that for minor diameter to major diameter ratios e in excess of 0.7, discrimination between elliptical and circular flaws is very difficult. For e less than 0.3, discrimination is easy. Consequently, the feature extraction and pattern classification techniques have been concentrated on e in the range 0.3 to 0.7 in order to establish the efficacy of the research protocol.” (Authors)