Effect of process parameters on joint quality and mechanical properties of local-thickened self-piercing riveted steel and die-casting aluminum joints

The self-piercing riveting is a major mechanical joining technique to join dissimilar lightweight materials, which has been widely used in the automotive industry. However, the die-casting aluminum sheet under the self-piercing riveted joint will generate cracks on the joint button due to the low ductility of the die-casting aluminum. A new technique of local-thickened self-piercing riveting (LT-SPR) is proposed to solve the problem of cracking on joint buttons in this paper. The effect of process parameters on cracking on joint button are discussed systematically and experimentally. The joint quality, mechanical properties, and failure mode of the LT-SPR joints are studied compared to the conventional SPR (C-SPR) joints. It is concluded that crack-free joints can be obtained in a wide range of rivet-die combinations using LT-SPR. Compared with the C-SPR joints, LT-SPR joints have larger forming quality indexes, smaller riveting force, smaller bending deformation, and better mechanical properties. For the LT-SPR process, the mechanical properties and failure mode are highly dependent on the rivet length, and larger rivet length can cause rivet fracture failure in the LT-SPR. The energy absorption of the joints that failed in interlock failure is superior to that of joints with rivet fracture failure, and joint strength is not affected by rivet fracture failure.