Laser-Generated Surface Skimming Longitudinal Wave Measurement of Residual Stress in Shot Peened Samples

Abstract

Shot peening is a surface enhancement technique that produces a compressive residual stress in a thin surface layer to extend the fatigue life and prevent stress corrosion cracking of structural components. A laser‐ultrasonic non‐contact technique is used for determining residual stresses produced by shot peening. The method is essentially based on the acoustoelastic effect of the laser‐generated surface skimming longitudinal wave (LSSLW) propagating just below the surface. The LSSLW is found to be more sensitive to residual stress than the Rayleigh surface acoustic wave. When used in combination with the Rayleigh surface wave, this laser ultrasonic technique is shown to be quite effective and provides results in good agreement with x‐ray data. Contributing factors such as surface roughness, crystallographic texture and dislocations have been examined and corrections for a satisfactory assessment of residual stress are proposed.