3D Simulation of magnetic field distribution in electromagnetic forming systems with field-shaper

Abstract

Impulse electromagnetic forming (IEMF) is an effective and powerful technique widely used for joining and shaping metals and field-shaper is a main part of the electromagnetic forming which has important effect on the distribution of magnetic field. In this technique, a metal work-piece is pushed to a die and formed by a pressure created using an intensive, transient magnetic field. This magnetic field is produced by passing a pulse of electric current through a forming coil in a pulsed power circuit. The produced transient magnetic field induces eddy currents in the surface of work-piece. Induced eddy currents in work-piece produce a magnetic field with reverse direction of initial magnetic field; this results in a mutual repulsion between coil and work-piece and in this way the work-piece is thrown toward the die. In this process created magnetic forces applied to work-piece are much like uniform, but in real applications, some regions of a work-piece have to be more deformed and therefore a much greater pressure has to be applied to these regions. The task of concentration of magnetic forces to some desired regions can be accomplished using field-shapers. Yu et al. [Yu, H., Li, C., Zhao, Z., Li, Z., 2005. Effects of field-shaper on magnetic pressure in electromagnetic forming. J. Mater. Process. Technol. 168, 245–249] have recently shown the effect of field-shaper on the distribution of the magnetic fields in electromagnetic forming, but because of the nature of 2D simulations some edge effects in real geometries could not be taken into consideration. In this paper, a 3D simulation using the FEA software MAXWELL has been applied to study the magnetic field distribution during an impulse electromagnetic forming process. Comparison of the 3D and 2D simulation results indicates that the maximum magnetic fields achieved in front of nodules of the field-shaper are about 15% stronger than those expected by 2D simulations. By changing the geometry of the field-shaper, the influence of the shape of the field-shaper on the distribution of the applied forces on the work-piece has been studied. Based on these simulations, some simple guidelines to design the field-shaper have been derived.