Fatigue failure analysis of welded structures: An overview and A case study

Abstract Fatigue failure analysis is essential for designing welded components subjected to cyclic loading. Real-world engineering structures will normally have welded components, which require a special consideration in the fatigue analysis process. In this chapter, global and local fatigue modeling approaches for welded structures are introduced. Local approaches are then discussed in more details and are used later to estimate the fatigue life of an automotive substructure. The required elements and the procedure for fatigue failure analysis and life estimation of a welded structure are explained. A case study for assessing the fatigue life of an automotive welded substructure is reviewed. The structure consists of three components, which are made of three different magnesium alloys. The components are joined together using the self-pierce riveting technique. Monotonic and fatigue test results for the base metals and welded specimens (with the same joining process as the structure) were obtained from the literature. The experimental results of the base metals show asymmetric hardening behavior under tension and compression. A local strain energy method was employed for fatigue modeling of the base metals and the welded specimens. To obtain the local strain energy, an asymmetric material model was employed to account for the asymmetric cyclic hardening behavior of the materials. Fatigue modeling of the welded structure was performed using the parameters obtained from the fatigue modeling of the specimens. Finally, the fatigue life and the failure location predicted by the fatigue modeling showed a good agreement with those obtained from fatigue testing of the structure.