Dependence of Load Angle on Static Strength of Resistance Spot Welded Lap Joint in Combined Load Test

Strength of resistance spot welded lap joint is a very interesting task. JIS prescribes tensile shear test and cross tension test as a realistic environment in combined load. Then, a lot of strength prediction equations have been proposed. And these features are in the use of a threshold value based on the base material strength as a fracture condition. The relational expression between the cross tension strength and the opening angle deals only with the influence of the opening angle on the axial force acting geometrically on the base metal. But it explains the experimental results well. The strength of resistance spot welded lap joint in combined load is known to exhibit dependence of load angle. But it is not clear whether the cause is only the geometric influence as shown by the past equations or the fracture mechanism change depend on the load angle. In this study, we examined how much dependence of load angle can be explained by macro geometric factors using a material dynamics model, before studying the micro fracture mechanism depend on the load angle in the vicinity of the crack initiation part of the nugget. As a result, we were able to explain the dependence of load angle with the macro model.