Fatigue Strength of Spot Welded Joints in a HSLA Steel

A wide variety of spot welded joints in a HSLA sheet steel were tested both in fatigue and statically, measuring the nugget rotation with load. Under static loads the load-nugget rotation plot was found to correlate well with a hyperbolic equation and the equation constants could be interpreted as a “theoretical load limit” and weldment “stiffness”. The influence of the number, shape and position of spot welds, weld defects and improvements, the loading couple and mode of loading on the fatigue strength of the spot welded joints were evaluated.