Improved Coil Design for Magnetic Pulse Welding of Metallic Sheets

Abstract

Magnetic pulse welding of overlapping dissimilar metallic sheets is an emerging technique and usually employs flat electromagnetic coils with rectangular-, H-, I-, and E-shaped cross-sections. The asymmetric cross-section of these coils results in a non-uniform electromagnetic field and in a non-uniform connection in the interface between the overlapping sheets. In this article, the use of a novel O-shaped flat coil is proposed to join an aluminium flyer sheet with a target steel sheet. A finite element-based numerical model is developed to calculate the electromagnetic field, flyer velocity, and its gradual impact onto the target, and the deformations of the sheet assembly. The calculated results with the O-shaped coil show a high-intensity electromagnetic field, the concentration of which decreases radially outwards in a uniform manner. The numerically computed and experimentally measured flyer velocity are found to be in fair agreement. The calculated results show a regularly decreasing impact behaviour between the flyer and target and their resulting deformation. The measured results show the formation of an annular ring-shaped joint profile that is generally found to be stronger compared to that obtained with flat coils with a rectangular cross-section.