Nondestructive Evaluation of Residual Stresses in Welded Joints with Application to Stochastic Fatigue Damage Accumulation

Abstract

Some of the most popular techniques for nondestructive evaluation of residual stresses in welded joints are described. Particular attention is paid to the X-ray diffraction and neutron diffraction method. The neutron diffraction method is the only nondestructive technique that is able to provide a complete, through-thickness distribution of the residual stresses in welded joints. The information on residual stresses is particularly important for fatigue damage calculation under stochastic loadings. It is demonstrated that the influence of residual stresses on stochastic fatigue damage accumulation may be incorporated by a simple approach based on elastic-perfectly-plastic material model and the Gerber correction factor. The model assumes that the remaining residual stress at the critical location depends on the largest nominal stress ever seen by a welded joint. The model predicts that the residual stresses during stochastic loading randomly decay to zero. The effect of material yielding is additionally investigated by considering an elastic-plastic material model with linear kinematic hardening. The residual stresses in this case are computed through Monte-Carlo simulations. It is demonstrated that the effect of material hardening is to reduce the rate of residual stress decay and thus to accelerate the rate of fatigue damage accumulation.