Stability of shot peening induced residual stresses and their influence on fatigue lifetime

▶ The shot peened specimens exhibit longer lifetime compared to unpeened ones as long as the residual stresses introduced by shot peening are reasonably stable. ▶ The stability of residual stresses is determined by the plastic strain amplitude and number of cycles during the fatigue loading. ▶ There is a linear equation correlating the residual stresses and the FWHM of the X-ray peak at any depth and total strain amplitude. ▶ Despite the relaxation of residual stresses which starts by start of plastic deformation, much longer lifetimes could be achieved for shot peened specimens provided that the amount and rate of relaxation are limited.