Effect of coil to tubular workpiece magnetic coupling on electromagnetic expansion process

Abstract

Efficiency of the electromagnetic forming process is very less. Leakage flux contributes to a fraction of total energy loss in the forming process, and it is related to the coupling between the coil and workpiece. The workpiece experiencing Lorentz force should be as close as possible to the tool coil in order to achieve higher utilization of discharge energy. In this paper, experimental and numerical simulation study is performed to observe the coil-tube magnetic coupling effect on tube expansion and thereby on process efficiency. Aluminum tube of 100 mm length and 1.5 mm thickness is electromagnetically expanded using a 7 turn helical coil. Trials are taken for the different gaps between the coil and tube whereas discharge energy kept constant. 2D sequentially coupled numerical simulation carried out using COMSOL software. The tube displacement and the coupling factor obtained in the simulation showed good agreement with experimental observations. The coupling factor decreases with increase in the coil-tube gap. The Process efficiency and tube displacement are found to be improved exponentially with increasing in coupling factor. Considering various design aspects, coil and workpiece should be tightly coupled to achieve higher process efficiency.