Resonant Scattering and Crack Sizing

Theoretical consideration of ultrasonic scattering from interior cracks has received considerable attention in recent years. These studies have led to scattering amplitude computations for ultrasonic backscatter from circular cracks by the method of optimal truncation (MOOT) (1, 2) and by T-matrix techniques (3). A key observation in these results is that a peak in the magnitude of the scattering amplitude is found to occur at approximately ka = 1, where k is the longitudinal wave number and a the crack radius, which is independent of the scattering direction. Up to the present, however, adequate experimental verification of these findings have been impossible due to a lack of suitable laboratory samples