Lamb wave scattering from a through hole

Ultrasonic guided waves, Lamb waves, are useful for evaluating the integrit y of plate and shell structures common in many applications. Tomographic re construction with Lamb waves allows for the accurate reconstruction of the variation of quantities of interest throughout the investigated region, and it presents the data as a quantitative map. The location, shape, and exten t of flaws can then be easily extracted from this tomographic image. The sc attering of Lamb waves from severe flaws introduces artifacts in such recon structions, however. In this paper higher order plate theory is used to der ive analytical solutions for the scattering of the lowest order symmetric L amb waves from a circular inclusion, focusing in particular on isolated thr ough holes in plates. Plane wave and point source scattering behavior is ex plored for holes of different diameters, and a finite-beam solution is cons tructed by superposition of point source solutions. These results are then used to explain the scattering effects seen in Lamb wave contact scanning t omographic reconstructions. (C) 1999 Academic Press.