In-situ Fault Detection by the Hybrid Ray-Mode Method.

摘要

The objective of this research effort has been to develop algorithms for in-situ location and identification, by ultrasound, of flaws in plates or laminated layered elastic materials. Achieving this objective requires detailed knowledge of the excitation propagation, scattering and detection of high frequency sound waves in unflawed and flawed environments. Based on an understanding of these fundamental wave phenomena, one may then attempt to construct analytical models with accompanying algorithms, so as to parametrize the NDE problem in terms of good observables. During this final period, the research program under the predecessor Grant No. AFOSR-86-0318 was phased out. Major effort was expanded on completing research items initiated under the predecessor grant, and on preparing, final manuscripts for publication. For the description of these previous studies, the readers should refer to the Final Report on the predecessor grant. A new phase was initiated during the current period, namely, a systematic study of nonspecular reflection of ultrasonic acoustic beams impinging from a fluid onto planar and cylindrical layered elastic materials. The nonspecular effect occurs when the incident beam is phase matched to a leaky mode in the structure and thereby causes the reflected field to be dominated by strong interaction between the specularly reflected beam profile and the leaky mode.