Study on fatigue fracture mechanism of 7075 Aluminum alloy clinching joint

Lightweight aluminum alloys are widely used in automotive structural parts, and clinching technology is one of the promising techniques for joining aluminum alloys. Since joint failure is mainly caused by fatigue failure, the fatigue properties of the clinched joints directly affect the reliability and safety of the connected specimens. Therefore, the static mechanical and fatigue properties of the Al7075 aluminum alloy single-lap clinched joints were studied using the static strength test and tensile-tensile fatigue test. The F-N curves of the joints were fitted using the straight-line fitting method and the three-parameter power function method. The fractured samples and wear scars were analyzed by scanning electron microscopy (SEM) and an energy dispersive spectroscopic technique (EDS). The results indicated that the neck of the clinched joint and the upper sheet near the joint had maximum fatigue fracture, and the fretting wear debris was mainly composed of alumina and metallic aluminum. The third type of fretting wear mode, i.e., inter-sheet of upper fretting wear mode, was found.