Shear testing of clinch joints at different temperatures: Explanation of the failure sequence

Abstract

Clinching is a reliable, high-speed, cost-effective, and environmentally friendly mechanical joining process that enables sheet metals to be joined in large scale productions including whiteware, ventilation and air conditioning systems and automotive applications. Currently, the mechanical behavior and durability of clinch joints under different thermal conditions is poorly understood. This study evaluates the mechanical performance of clinched joints at room temperature, 100 °C and 250 °C experimentally using uniaxial shear tests. Results revealed that all clinched specimens had a similar shaped load displacement curve. Four stages were observed: an initial linear behavior with low sensitivity to temperature; a force plateau caused by necking (the force was only moderately reduced for higher temperatures); a phase where the neck began to crack, resulting in a letdown of the load which showed high thermal dependence, and a final phase of tearing completely through the neck, with joint separation. The ultimate tensile shear strength of the joints was relatively unchanged by increases in temperature. At higher temperatures the stiffness and energy absorbed by the joint decreases. This work shows the results of thermal shear testing for clinched joints, and describes the mechanisms whereby the joint progressively collapses under load.

Keywords

• Clinching
• Metal forming
• Mechanical behavior
• Shear test
• Thermal shear test
• Failure mode