Nowadays, the widespread use of resistance spot welding (RSW) in various industries is evidence for the importance of this manufacturing process. In this paper, the finite element method (FEM) is utilized to model the weld nugget geometry and tensile-shear strength in RSW process of the galvanized interstitial free (IF) and bake hardenable (BH) steel sheets. Computational results have good agreement with experimental data. The investigation of input parameters influence, namely welding current, welding time, and electrode force on nugget size variations reveals that welding current is the most influential parameter. The examination of input parameters interaction on joint strength indicates that increase in welding current and time and also reduction in electrode force result in larger nugget size and bigger joint strength. Although by increasing the nugget size, at first, the joint strength is raised, after reaching the maximum strength, increase in nugget size results in decreasing the joint strength, and it may lead to expulsion phenomenon. The analysis of variance (ANOVA) results of response surface methodology (RSM) modeling demonstrate that beside the welding parameters, their interactions have significant effect on nugget geometry and tensile-shear strength. The relative error between RSM predicted and FEM calculated maximum strength is attained about 3% that specifies the efficiency of RSM.

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