Improvement in joint strength and material joinability in clinched joints by electromagnetically assisted clinching

Abstract

An electromagnetically assisted clinching process is proposed to join a combination of similar and dissimilar materials using a high-speed punch. As the name suggests, an electromagnetic discharge energy is used to accelerate the punch to sufficiently high speeds. Joining similar and dissimilar combinations of carbon fiber reinforced plastic (CFRP) and aluminum sheets is conducted as the case studies to investigate the performance of the technique. The mechanical behaviour and failure modes of the joints are studied using single-lap shear tests. Superior undercut, neck thickness, and resultantly superior joint strength is obtained compared to the conventional clinching techniques, thanks to the combined effect of thermal softening and strain rate dependent hardening in the joining zone. Such an improvement in the joint strength could be achieved in all strain rate sensitive materials. The influence of the processing and tooling parameters particularly the discharge energy, and toolset geometry are investigated on the joint strength and failure modes. It is suggested to use an optimum range of the discharge energy with respect to the thickness, ductility, yield strength and other mechanical properties of the joining partners especially punch-sided one.