Material Brittleness and the Energetics of Acoustic Emission
This paper will review energy aspects of the acoustic emission (AE) phenomenon and its relationship to material properties especially brittleness. The spectral energy density of the AE wave at low frequencies is related to the moment tensor, but this is only a fraction of the total energy converted in the deformation or damage process. The “conversion efficiency” from static elastic energy to dynamic AE energy is governed by the source speed, and this in turn is related to the brittleness of the material. Meanwhile, the spectral bandwidth of the AE near the source is governed by the duration of the source event. The resulting relationships between brittleness and acoustic emissivity will be discussed. Examples will be drawn from metals, fiber reinforced composites and geological materials. A further factor that has a strong influence on a material’s damage tolerance is its heterogeneity. This also has a strong influence on its acoustic emissivity, specifically on the amplitude distribution. In a recent development in the practical application of AE to industrial plant monitoring, these factors and others are integrated in a model of the Probability of Detection (POD) for fatigue cracks growing in a mixed mode comprising both ductile and brittle deformation mechanisms.
KeywordsFatigue Manganese Brittle Molybdenum Convolution
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- 1.Standard Terminology for Nondestructive Testing, E 1316, ASTM Book of Standards, Volume 3.03, published annually.Google Scholar
- 2.Pollock, A. A., Acoustic Emission from Solids Undergoing Deformation, Ph.D. thesis, University of London, p. 202, April 1970.Google Scholar
- 4.Pollock, A. A., A POD Model for Acoustic Emission – Discussion and Status, Review of Progress in Quantitative Nondestructive Evaluation, Vol. 29B, AIP Conf. Proc. Volume 1211, pp. 1927–1933, 2009.Google Scholar
- 5.Pollock, A. A., Acoustic Emission Amplitude Distributions, International Advances in Nondestructive Testing, Ed. Warren J. McGonnagle, Vol 7, pp. 215–239, 1981.Google Scholar
- 6.Mogi, K., Study of Elastic Shocks Caused by the Fractureof Heterogeneous Materials and its Relations to Earthquake Phenomena, Bull. Earthqu. Res. Inst. Vol. 40, pp. 125–173, 1962.Google Scholar
- 7.Scholz, C. H., The Frequency-Magnitude Relation of Microfracturing in Rock and its Relation to Earthquakes, Bull. Seis. Soc. Am. Vol, 58, No. 1, pp. 399, 415, February 1968.Google Scholar
- 8.Pollock, A. A., Physical Interpretation of AE/MA Signal Processing, Proceedings, Second Conference on Acoustic Emission / Microseismic Activity in Geologic Structures and Materials, Pennsylvania State University, Edited H. R. Hardy and F. W. Leighton, Trans Tech Publications, pp. 399–422, 1980.Google Scholar
- 9.Yuyama, S., Acoustic Emission for Fracture Studies Using Moment Tensor Analysis, J. Strain Analysis, Vol. 39, No. 6, Special Issue Paper S08103, 2004.Google Scholar
- 10.Aki, K. and Richards, P.G., Quantitative Seismology, Second Edition, University Science Books, 2002.Google Scholar
- 11.Wadley, H. N. G., Scruby, C. B. et al, Acoustic Emission During Deformation and Fracture of Aluminium Alloys: Uniaxial Tests, AERE - R 10362, United Kingdom Atomic Energy Authority, 1981.Google Scholar
- 12.Acoustic Emission Testing, Volume Five, Nondestructive Testing Handbook, Second Edition, American Society for Nondestructive Testing, pp. 77–83, 1987.Google Scholar