2024 Volume 80 Issue 15 Article ID: 23-15028
Improvement effects of fatigue strength by post-welding treatment methods, for instance grinding and hammer peening, have attracted considerable interest. Improvement of the weld toe shape and compressive residual stress are considered to enhance fatigue performance of welded joints. However, individual effects are not clear, since those treatments change simultaneously the local residual stresses and the weld toe shape. Recently, the authors studied on a method to predict the fatigue crack initiation life by using the local strain approach and extended it to assesst the crack propagation life, handled as continuous behavior of crack initiation life. The prediction of the inelastic deformations has been investigated by means of an unconventional elasto-plasticity model called the Fatigue SS Model (hereafter, FSS model). The FSS model is based on the Subloading Surface theory, which was enriched by including the elastic boundary and cyclic damage concepts for the description of strain softening behavior within macroscopically elastic stress state. The FSS model was used to investigate the inelastic response of the material under different cyclic loading conditions. The aim of this paper is to study the welding residual stress and shape effects on the fatigue performance of welded joints. In this study, finite element analyses were conducted to assess the fatigue crack initiation and propagation lives of a non-load carrying welded fillet joint by using the local strain approach. The results show that the fatigue life of welded joints can be enhanced by removing tensile welding residual stresses, or reducing welding deformation, or improving weld toe shape. In particular, the most effective improvement on the fatigue life is obtained by reducing the welding deformation.
