Ultrasonic Evaluation of Residual Stresses in AISI 316Ti Steel Specimen after Laser Shock Peening

Residual stresses induced by laser shock peening in the near-surface layer in AISI 316Ti austenitic stainless steel specimen were measured by ultrasonic technique using critically refracted longitudinal waves. The results of ultrasonic measurements were compared with the results obtained by hole drilling method. The values of the residual stresses induced by laser shock peening, the initial residual stresses in the rolled sheet and the yield strength of the material were compared. The thermal stability of laser-induced residual stresses after annealing the specimen for 5 hours at the temperature of 200 °C and re-annealing for 5 hours at the temperature of 280 °C was investigated. The results of study were analyzed taking into account the accepted assumptions, limitations and uncertainties. The structure near the untreated and laser-treated surface was studied using optical and scanning electron microscopes. The directions of further studies for the development of nondestructive technique for ultrasonic evaluation of residual stresses induced by laser shock peening of the surface were proposed.