Relaxation of Residual Stresses Induced by Ultrasonic Shot Peening Due to Cyclic Loading

Abstract

Conventional Shot-Peening is one of the popular surface enhancement processes. It consists on projecting small shots at the surfaces of the metallic components. Ultrasonic Shot-Peening is based on the same principle. The differences between both mechanisms were: the size of shot (from 0, 25 and 1 mm for Conventional Shot-Peening, and 1 to 8 mm for Ultrasonic Shot-Peening) and the velocity (from 20 to 150 m/s for Conventional Shot-Peening, and 3 to 20 m/s for Ultrasonic Shot-Peening). Another difference is the mechanism used for projecting the shots. In Ultrasonic Shot-Peening process the shots, confined in a closed chamber, are projected by sonotrode vibration on the treated specimen that is fixed on the top of this chamber. So, during the Ultrasonic Shot-Peening, the shots can be recovered after the treatment. In this paper, we propose three dimensional finite element model of Ultrasonic Shot-Peening which enable predicting the residual Stresses generated by this process on a semi-infinite target after a repetitive impacts. Moreover, this model is used to evaluate the residual stresses relaxation in AISI 316L target under cyclic tensile loading. The numerical results are validated by comparing the residual stress profile induced by the numerical model with the experimental findings.