Shunting Effect in Resistance Spot Welded Joints of Aluminum Alloys

Shunting effect occurs in RSW when the electrical current passes through previous spot welds. Value of this current depends mostly on distance, number, and size of previous spot welds. This will cause some dimensional and metallurgical changes in welding nugget as well as heat affected zone (HAZ). In this study, shunting effect of RSW is considered in a finite element analysis (FEA) model and the results are compared to experiments performed on aluminum alloy 2219. Weld spacing together with welding current and time are considered to discover the effect of shunting current in the final quality of nugget. A three factor experiment design has been performed to find the significance of factors and interactive effects, as well as FEA model verification. Electrothermal and mechanical interactions are considered in the FEA model. Experimental and numerical solutions have yielded comparable similar results in terms of welding nugget properties. Asymmetry in electrical potential, temperature, and stress distribution and geometry of shunted nugget are predicted and verified directly or indirectly. Intense effect of shunting current on nugget height, asymmetric growth of heat affected zone (HAZ) toward previous welding nugget, as well as concentration of alloying elements along grain boundaries are also discovered.