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

Abstract

The strength of resistance spot welded lap joints is very important. JIS prescribes tensile shear testing and cross-tension testing as a realistic environment under combined load. Thus, numerous strength prediction equations have been proposed. These equations use a threshold value based on the base material strength as a fracture condition. The relationship between the cross-tension strength and the opening angle only reflects the influence of the opening angle on the axial force acting geometrically on the base metal. However, it shows good agreement with the experimental results. The strength of resistance spot welded lap joints under combined load is known to be dependent on the load angle. However, it is not clear whether the only cause for this is the geometric influence as indicated by previously established equations or whether the fracture mechanism changes depending on the load angle. In this study, we examined the extent to which the dependence on load angle can be explained by macro geometric factors using a material dynamics model, before studying the micro fracture mechanism, which depends on the load angle in the vicinity of the crack initiation site in the nugget. Thus, we were able to explain the load angle dependence with a macro model.

 

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 82 (2018) 59–63.