Design of axial/torque joint made by electromagnetic forming

Recently, weight reduction of vehicles has been of great interest, and consequently, the use of low-density materials in the automotive industry is increasing every year. However, the substitution of one material for another is not simple work. Simple substitution of material cannot achieve stiffness and strength, so that the structure of the automobile should be redesigned totally. Spaceframe is rapidly being adopted as a body structure for accommodating lightness, stiffness and strength requirement. In spaceframe manufacturing, it is often required to join tubular parts with different cross sectional shapes and different materials. But there are few suitable methods for satisfying these requirements, so that much interest has been focused on testing suitable joining methods. Joining by electromagnetic forming (EMF) can be useful method in constructing spaceframe. It offers some advantages compared with the conventional joining method such as welding. In this paper, joining by EMF was investigated as a pre-study for application to an automotive spaceframe. Finite element simulations and strength tests were performed to analyze the influence of geometric parameters on the joint strength. Based on these results, axial joint and torque joint were designed and guidelines for designing EMF joint were established.