Modelling and Optimization of Resistance Spot Weld Responses Using RSM–GA Technique for DP590 Steel Sheets

Resistance spot welding of DP steel sheets possesses a significant application in the automotive industries. Thus, welding process parameters to be taken during the process of joining are critical to concern. In the present study, resistance spot welds of DP590 steel sheets fabricated to acquire the weld responses, i.e. shear-tensile strength, coach-peel strength, mean dynamic contact resistance, and nugget diameter. The experiments for weld fabrication were designed incorporating the face-centred central composite design under response surface methodology (RSM). Sensitivity of the process parameters was also analyzed. Response models obtained are optimized using the genetic algorithm (GA) for multi-objective optimization to get optimum spot weld process parameters. End failure analysis of the weld specimens was performed for both shear-tensile test and coach-peel test using the SEM fractographs. Shear-tensile strength is more sensitive to the weld current (I) and electrode force (F) as compared to the weld time (T). Shear-tensile test specimens were found to fail through IF and PF modes, while coach-peel test specimens were found to fail through PIF and PF modes. Predicted models using RSM methodology are significant and within the adequate precision. It is observed that the optimization using hybrid RSM–GA is found to be better than that using design expert for different responses.