Visualization of surface elastic waves on structural materials

A technique developed by Adler, Korpel, and Desmares for the visualization of surface elastic waves has been applied to the problem of inspecting structural materials. The technique produces a stationary display of the crests and troughs of a travelling surface wave, much as would occur under stroboscopic illumination. Changes in the local elastic properties on or near the surface are indicated by scattering and distortion of the wavefronts. Photographs are presented illustrating the use of the technique both in locating defects and in studying the intrinsic properties of materials. The examples include thickness variations and holes in sheets and plates, cracks in surfaces, and metallurgical variations in nominally defect-free material.