Grain structure visualization with surface skimming ultrasonic waves detected by laser vibrometry

Abstract

Laser vibrometry was used to visualize the process of ultrasonic wave propagation on a metallic sample surface. We were able to image the material microstructure from a sequence of high resolution laser vibrometric snapshots of the wave field. This information is usually hidden by the large amplitude of the propagating wave, but we were able to extract it by appropriate evaluation of the measured data. The method was applied to an austenitic weld specimen; the grain structure information obtained by this approach strongly resembles metallographic micrographs.