Nugget shifting in resistance spot welding of multi-stackup sheets

Abstract

In order to investigate the weld nugget shifting phenomenon in resistance spot welding, a combined thermal-mechanical-electrical finite element model was developed to analyze the weld nugget formation process during welding. It was found that when the thickness of the bottom sheet increases, the degree of weld nugget shifting would become serious which will lead to the unqualified weld nugget. For the welding joint with material combination of SAE1004 + SAE1004 + DP600, the critical thickness combination is 0.6 + 1.8 + 2.0 mm. To improve the weld nugget shifting of the multi-stackup sheets joint, different electrode tips were used in the welding process. The effectiveness of this method was validated by the metallographic pictures.