Experimental study on the height-reduced joints to increase the cross-tensile strength

Mechanical clinching technology for joining aluminium alloy sheets has been a hot research topic in recent years. However, the clinched joint has a lower static strength than the welded joint and self-pierce riveted joint. In order to increase the strength of the clinched joint, a height-reducing method was investigated in the study. The material of the sheets is AL5052 which is widely used on the automotive body. Extensible dies were used to produce the clinched joint, while a flat die and a bumped die were used to produce the height-reduced joint. In the height-reducing process, the protrusion of the clinched joint was compressed by the flat die. The material of the protrusion flowed to the neck, which increased the strength of the joint by increasing the neck thickness. Different joints with different geometrical parameters were used to conduct the cross-tensile tests. The cross-tensile strength, energy absorption, failure mode and geometrical parameter of the joint are investigated. The results show that the cross-tensile strength and energy absorption of the joint can be increased by the height-reducing process. The main failure mode of the joints is neck fracture mode. The height-reducing method can increase the neck thickness with the decrease of the protrusion height. The height-reducing method was proved to be effective for increasing the strength of the clinched joint.