Experimental Study on Resistance Spot Welding of Unequal-Thickness Steel Sheets: Weld Nugget Characteristics and Failure Behavior

Considering wide application of dissimilar-thickness resistance spot welds in automotive industry, investigating their failure behavior is of utmost importance. The aim of this paper is to investigate the weld nugget characteristics, failure mode and failure mechanism of dissimilar thickness low carbon steel resistance spot welds during tensile-shear overload test. Mechanical properties of the joints were described in terms of peak load, energy absorption and failure mode. It was found that for well-established weld nuggets, the final solidification line is located in the geometrical centre of the joint. In pullout failure mode, failure is initiated by necking of the base metal at the thinner thickness sheet. Finally, it was concluded that weld nugget size, weld penetration and the strength of the thinner sheet are the main controlling factors of the load bearing capacity and energy absorption capability of dissimilar thickness spot welds.