Scattering of Impulsive Acoustic Waves by a Semi-Infinite Crack in the Plane Interface of a Half-Space and a Layer

摘要

The problem investigated has its relevance to the quantitative non-destructive evaluation of mechanical structures. For the mechanical structure, a flat layered model is introduced. In the lower boundary of the layer a semi-infinite crack is present and the response of the configuration to an acoustic pulsed line source is requested with both source and observer located anywhere on the surface of the structure. The problem is modeled as a two-dimensional acoustic diffraction problem suitable for the application of the Wiener-Hopf technique. Subsequently, a solution in the time domain due to a pulsed line source excitation is sought with the help of the modified Cagniard technique. A related diffraction problem in electromagnetics is studied by Du Cloux. However unlike in Du Cloux's problem, the presence of the layer next to the diffracting edge gives rise to guided wave effects, with considerable consequences for the analysis. A recursive scheme is developed leading to a formal series solution of the problem. Numerical solutions pertaining to a finite time window of observation are presented.