Spot welding, one of the electric resistance welding, is widely used in joining metal processing. Most of spot welding points are exposed to stress concentration, therefore fatigue cracks are initiated from spot welding for most of spot welded structures. Fatigue life assessment of spot welded structure is an important role to retain structural safety and durability. Fatigue assessment of spot weld is not an easy task, since evaluation of the fatigue parameters such as stress around the nugget, stress intensity factors, and so on, is very difficult. Various methods and finite element modeling techniques for spot welding fatigue assessment are developed. However, these methods still require user`s determination based on the in-depth field experience.
In this study, structural stress approach is used to access fatigue life of spot weld. Some simple bar-shell type spot weld finite element modeling techniques are analyzed numerically with various nugget diameter and sheet thickness to provide the most effective one. An attempt is tried to provide new spot welding finite element modeling technique to consider nugget stiffness. The proposed method is based on simple bar-shell connection spot welding modeling, and it holds nugget stiffness by overlapping triangular element nugget patch on the existing mesh. A few spot weld specimens are tested numerically by each spot welding methods and the proposed method. The proposed method produces the consistent result.
