Characterizing Shunting Effects on Nugget Quality and Joint Strength in Sequential Spot Welds for Automotive Applications

Typical automobile assembly operations need thousands of resistance spot welding in series with closely spaced spots due to their complex structural designs. This inevitably leads to shunting-induced current diversion, adversely affecting weld quality. The extent of this shunting loss varies depending on parameters such as spot pitch and sheet thickness, making universal parameter optimization challenging. This study experimentally and numerically investigates the influence of shunting on nugget formation and joint strength, considering varying workpiece thicknesses and spot pitches. Results indicate that shunted welds experience up to 18% reduction in nugget area and 6% reduction in joint strength, with further reductions of up to 47% for thicker sheets and smaller spot pitches. To mitigate shunting effects, increasing the welding current in proportion to the loss of current density effectively restores nugget size and weld uniformity. The proposed solution and developed model offer a robust approach for industrial implementation, ensuring weld consistency and structural reliability in automotive applications.