Innovatively Joining Thin Al Alloy Sheets Using the Synergistic Effect of Rotating and Stationary Shoulders and Joint Mechanical Properties

In this work, thin Al alloy sheets were first joined by the synergistic effect of rotating and stationary shoulders. A tool system combined with an inner rotating shoulder and an outer stationary shoulder was designed. The inner rotating shoulder is mainly used to produce essential heat input, and the outer stationary shoulder is mainly used to enhance the metallurgical bonding and eliminate arc corrugation and flash. The results show that sound joints without flash and arc corrugation are obtained by this newly proposed method. Hooks and cold laps are very small inside the joints, and their heights gradually decrease with an increase in the rotating speed from 400 to 1000 rpm. The hardness and lap shear failure loads of the joints welded by the tool with rotating and stationary shoulder are higher than that welded by a traditional tool because of less heat input during welding. The lap shear failure load of the joint first increases and then decreases by increasing the rotating speed. The maximum failure load of 5364 N is obtained at 600 rpm, and the joint shows tensile fracture mode.