Numerical Prediction of Tool Rotation Speed for Optimum Mechanical Properties of Weld Joint in Friction Stir Welding of Dissimilar Aluminum Alloys

This research paper describes a numerical approach for determining the optimal tool rotation speed (TRS) to achieve superior mechanical properties in friction stir welding (FSW) of dissimilar aluminum alloys, specifically AA5083-H12 and AA6061-T6. For this purpose, computational fluid dynamics (CFD) coupled with the volume of fluid (VOF) method is employed to develop a numerical model for FSW. The temperature and material flow numerical model are simulated at five different TRS (710, 900, 1120, 1400, and 1600 rpm), the model explores temperature, material flow variations, and slip rates with different TRS levels. The mechanical properties are correlated with numerical analysis. Results indicate that material flow velocity near the shoulder increases as increases the TRS from 700 to 1600 rpm. However, the trend in material flow velocity changes after reaching 1120 rpm near the bottom of the tool-workpiece interface. This decrement is attributed to temperature-induced material accumulation and slip rate affecting the uniformity of contact conditions at the tool-workpiece interface. Near the bottom of the weld, slip rates increase initially with TRS from 710 to 1120 rpm but decrease thereafter. Lower slip rates at 1400 and 1600 rpm indicate increased sliding, leading to defects and reducing the tensile strength in weld joints. Optimal tensile strength of 174 MPa and an improved ductile fracture mode compared to all weld joints is obtained at 1120 rpm.