A New Technique for Distinguishing Internal Voids from Solid Inclusions
An acoustic microscope has been proven to be a very effective tool for visualization and characterization of small internal defects in solids[l]. The distinction of internal defects such as cracks and voids from solid inclusions is sometimes necessary for material evaluation. For example in case of light metal casting alloys ultrasonic scattered echo from pores and heavy metal inclusions used for strengthening purposes can give the ultrasonic signal of the same order of magnitude . In this paper it is shown how the phase information of the reflected echo can be used to distinguish void signals from solid inclusion signals. Conventional acoustic imaging techniques that use only amplitude information and ignores the phase information can not distinguish between voids and inclusions.
KeywordsCarbide Epoxy Tungsten Gelatin Cose
Unable to display preview. Download preview PDF.
- 1.A. Briggs, “Acoustic Microscopy”, Clarendon Press, Oxford, 1992.Google Scholar
- 2.J. Krautkramer, H. Krautkramer “Ultrasonic testing of materials” Springer-Verlag, Berlin Heidelberg, N.Y. 1983., p. 536.Google Scholar
- 3.L.M. Brekhovskikh, “Waves in layered media” Academic Press, N.Y., 1960.Google Scholar
- 5.D.E. Fitting, L. Adler, “Ultrasonic Spectral Analysis for Nondestructive Evaluation”, Plenum, N.Y. 1981, pp. 106–109.Google Scholar
- 11.A. Stockmann, P.S. Nocholson, “Ultrasonic Characterization of Model Defects in Ceramics—Voids in Glass—Theory and Practice”, Mat. Eval., 44, pp.756–761, (1986).Google Scholar
- 12.A. Stockmann, P. Mathieu, P.S. Nocholson, “Ultrasonic Characterization of Model Defects in Ceramics (part 3). Spherical Inclusion in Opaque Crystallized Glass — Theory and Practice, Materials Evaluation”, 47 (3) pp. 356–362, (1989).Google Scholar
- 13.O.I. Lobkis and P.V. Zinin, “Acoustic microscopy of spherical objects. Theoretical approach”, Acoust. Lett. 14, 168–172,(1991).Google Scholar
- 15.L. Paradis, J.F. Salin, “Non destructive evaluation of the mechanical characteristics of plasma sprayed ceramic coatings” in Review of progress in quantitative nondestructive evaluation, 13B eds. D.O. Thompson and D.E. Chimenti, Plenum N.Y. 1994, pp. 1229–1236.Google Scholar
- 16.O.V. Kolosov, O.I. Lobkis, K.I. Maslov, P.V. Zinin, “The effect of the focal plane position on the images of spherical objects in the reflection acoustic microscope”, Acoust. Lett. 16, pp. 84–88 (1992).Google Scholar
- 17.O.I. Lobkis, K.I. Maslov, T. Kundu, P.V. Zinin, “Spherical Inclusion Characterization by the Acoustic Microscope: Axisymmetric Case”, J. Acoust. Soc. Am, in press (1995).Google Scholar
- 18.Y. Sasaki, T. Endo, T. Yamagishi and M. Sakai, “Thickness measurement of a thin film layer on an anisotropic substrate by phase-sensitive acoustic microscope”, IEEE Trans. UFFC. 39, pp. 638–642 (1992).Google Scholar