ASA 125th Meeting Ottawa 1993 May

5pPA5. Scattering from partially contacting interfaces.

J. G. Harris

E. Yogeswaren

Theoret. Appl. Mech., UIUC, 216 Talbot Lab., 104 S. Wright St., Urbana, IL 61801

Fatigue cracks and diffusion bonds are two common objects of nondestructive inspection. Both are characterized by extensive regions of rough, partially contacting interfaces, where the characteristic size of a void or asperity is much smaller than the compressional wavelength in the material, at frequencies on the order of 100 MHz. Work describing efforts to characterize scattering from such an interface, including the effects of multiple scattering, is described. The multiply scattered wave fields are calculated by solving scalar or vector integral equations. Two formulations will be discussed. One uses a specific interface model consisting of multiple, small cracks having arbitrary lengths and spacings, while the other uses a more general formulation called a polarization theory [G. Wickham, J. Nondestr. Eval. (to appear in 1993)]. The scattered wave fields are then used in a measurement model, whose purpose is to emulate the effects that the emitting and receiving transducers have upon the incident and received signals. Both scattering by an incident plane wave and by a focused beam are discussed. [Work supported by NSF.]