Effect of Initial Damage on Fatigue Performance of Welded Joints

In order to investigate the effect of initial damage of a welded joint on its fatigue life and damage evolution, adopting the damage variable based on crack size from the damage mechanics, two common fatigue damage evolution models, the Chaboche model and the Lemaitre model, were used to discuss the effect of the initial damage on the fatigue life and damage variable of the welded joint, and a concept of fatigue life reduction factor that is based on the initial damage was proposed. Then, the fatigue life reduction factors and fatigue damage curves under different initial damage were obtained from a non-carrying fillet welded joint in a case study. The results show that when the initial damage is less than 0.055 or 0.002, its effect on the fatigue life can be ignored in both the Chaboche model and the Lemaitre model. The Lemaitre model is more sensitive to the initial damage than the Chaboche model, and the Chaboche model is more appropriate to describe fatigue damage evolution of welded joints.