Decay of Residual Stress in Stochastic Fatigue

Abstract

Random-amplitude fatigue situations are studied to determine the possible effects of residual stresses induced by the welding of the specimens. Experimental results show that large-amplitude precycling of a welded specimen can significantly extend its fatigue life under small constant-amplitude loadings, and that this effect is consistent with the results of the Gerber formula for the effect of mean stress, along with an assumption of elastoplastic stress-strain behavior of the specimen. This model predicts that the remaining residual stress at the critical location in the specimen is a function of the largest load that has ever been applied to the specimen. For a stochastic loading this implies that the mean stress gradually decays in a random manner throughout the fatigue life of the specimen. Numerical results show that the stochastic fatigue life may be significantly extended beyond that predicted by neglecting the decay of residual stress.