Optimization of friction stir spot welding process parameters for Al-Cu dissimilar joints using the energy of the vibration signals

A friction stir spot welding (FSSW) process for dissimilar aluminum alloy AA1050 and pure copper sheets of 3-mm thickness at different tool rotation speeds between 710 and 1800rpm and dwell time levels of 0, 5, and 10s were performed in this study. Empirical relationships were developed to predict the shear failure load (joint strength) and the energy of the vibration signals incorporating two of the most important process parameters, tool rotation speed and dwell time. Process parameters were optimized by using the response surface method (RSM); the optimal values of tool rotation speed and dwell time were 1255rpm and 4s, respectively. The parameters optimization results were used in a confirmation test; the dissimilar Al/Cu FSSW joints made with optimal parameters exhibit a good shear failure load. The close relationship between the shear failure load (SFL) of the welded joint and the energy of the vibration signals (EVS) generated during FSSW process was demonstrated. This model can be used to develop and optimize the parameters for automatic control of the FSSW process, based on the vibration signal generated.