ANTIPLANE ELASTIC-WAVE SCATTERING FROM A ROUGH VOLUMETRIC CRACK

The scattering of elastic waves from cracks is a field of study which has a number of important applications in nondestructive testing (NDT) and characterization of materials. So far most theoretical studies ha ve concerned smooth cracks. There is reason to believe that the influe nce of roughness will scatter the energy in a more diffuse way, thus c omplicating the interpretation of test results. The problem considered here is the scattering of anti-plane waves, i.e. ''horizontally'' pol arized shear waves, from a crack in an otherwise homogeneous, isotropi c, elastic solid. The geometry is taken to be two-dimensional, and the scatterer is a curved volumetric crack with a small random roughness, which is characterized by the RMS height and a correlation length whi ch is related to the average distance between the peaks of the irregul arities. The term ''volumetric'' refers to the fact that the crack sur faces are slightly separated. Effects due to overall curvature as well as effects due to surface roughness and separation of the crack surfa ces are thus included in the analysis. The method of solution can be d escribed as an extension of the null field approach where certain matr ix elements are expanded in terms of a small parameter describing the deviation from the smooth, nonvolumetric crack. The ensemble averaged amplitude of the scattered field for an incident plane wave has been c omputed numerically. Some results are given for various values of the frequency, the RMS height, the correlation length and the maximum gap between the crack surfaces. Copyright (C) 1996 Elsevier Science Ltd.