Effect of Welding Current on Nugget Dimensions and Residual Stress Distribution in Resistance Spot Welding Process

Resistance Spot Welding is being used in the industry for sheet joining process especially in the automobile and aerospace industry. Resistance spot welding method involves electrical, thermal and mechanical interactions. These make the whole welding process highly nonlinear and difficult to model. Weld nugget size is the most effective parameter in mechanical characteristics of resistance spot welded joints. Also residual stresses generate in the welded joint because of high temperature gradients during the welding process and electrode force. Tensile residual stress accelerates the fatigue crack propagation in components so accurate and comprehensive information about the residual stress distribution is needed to design the components perfectly. Welding current is the main parameter of resistance spot welding process that affects on the nugget dimensions and residual stress distribution. In this study, a ۲D axisymmetric electro-thermomechanical FE model is developed in ANSYS to investigate the effect of welding current on nugget size and residual stress distribution in resistance spot welding of steel sheets. Experimental and numerical results show decrease in nugget growth rate withincreasing welding current for steel sheets. The maximum tensile residual stress is located at the center of the weld nugget. The level of tensile residual stress in steel sheets is increased with the welding current increase because the thermal strain is increased.

Keywords:

resistance spot welding , nugget dimensions , residual stress , welding current , finite element model