Rotated clinching process for two-layer metallic sheets

Mechanical clinching is a process of joining various sheets using a punch and a die and has been widely applied in automobile manufacturing. A rotated clinching process using two rotated heads and a flat-bottomed fixed die was proposed in this study. An experimental device was developed and rotated clinching experiments were conducted on 1.5-mm-thick Al1060 sheets using this approach. Shear and pull-out tests of the joints with various vertical reductions of rotated heads were conducted to evaluate the static joining strength. The failure modes of joints and the geometric characterisation of the joint profile in terms of interlock and neck thickness were analysed. Preliminary test results show that the joint strength exhibited evident directionality, where the force applied in the transverse direction was the largest. The maximum strength was 40% that of the Al1060 sheet. Full tearing failure and partial tearing with unbuttoning failure were the main joint failure modes. With increasing vertical reduction of the rotated heads, the neck thickness changed less and the interlock increased, reaching 33.3% of the lower sheet thickness.