Evaluation of residual stress using SAW

The frequency dependency of the Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in the scuffing specimens, and then compared to the residual stress distribution. The width and of the backward radiation profile increases and the peak intensity decreases as the increase of variational rate of residual stress distribution for the scuffing specimen. The peak angle depends on the amount of residual stress and plastic deformation, etc. The spectrum of backward radiated wave shows that the surface wave is scattered by micro-fatigues during the propagation. The result observed in this study demonstrates high potential of the backward radiated ultrasound as a tool for the nondestructive evaluation of the subsurface gradients of materials.