Effect of welding nugget diameter on the fatigue strength of the resistance spot welded joints of different steel sheets

This paper presents an experimental study on the fatigue strength of resistance spot welded galvanized steel sheets and austenitic stainless steel (AISI 304) sheets. The sheet materials were joined by using resistance spot welding as a lap joint. Material combination and nugget diameter were selected as experimental parameters. The high cycle fatigue tests were performed and S–N curves were obtained for each specimen. The results show that galvanized steel sheet combination has the highest fatigue limit. The sheet combination which has the minimum fatigue limit is galvanized–AISI 304 sheet combination. For austenitic stainless steel–galvanized steel sheet joint, the measurements of the nugget diameter and crack length were performed after fatigue tests. Crack growth rate of the spot welded galvanized–AISI 304 joining type is slower than that of base metals given in literature. C and m coefficients of Paris–Erdogan equation for spot welded AISI 304–galvanized steel sheet joints were obtained.