Optimizing friction stir welding parameters for specific energy of aluminum alloys

Friction stir welding (FSW) is a promising joining technique with low environmental impact. Considering the importance of adequate selection of FSW parameters for weld quality and energy consumption, this study presents an optimization of specific energy considering constraints. The Newton optimization method is used to find the optimal values of process parameters. The specific energy consumed during the FSW is calculated from the expression for the torque variation as a function of the process velocities and tool geometry. The constraints are imposed to ensure selected parameters produce defect-free welds and are defined based on the literature review. The specific energy is optimized to find the optimal values of welding speed, rotational speed, shoulder radius, and pin radius of the tool. Additionally, the power is analyzed at the minimum specific energy condition. The results show that a welding speed of 200 mm/min and a tool rotational speed of 400 rpm minimize the specific energy consumed. Moreover, for plates with a thickness between 3 and 6 mm, the optimal values of shoulder radius and pin radius for the minimum specific energy are 10 mm and 3.8 mm, respectively. In the same way, for plates with a thickness between 7 and 9 mm, the minimum specific energy is obtained for a shoulder radius of 13.90 mm and a pin radius of 5.08 mm.