Analysis of Proximity Consequences of Coil Windings in Electromagnetic Forming

Abstract

Multiturn coils are required for manufacturing sheet metal parts with varying depths and special geometrical features using electromagnetic forming (EMF). Due to close coil turns, the physical phenomena of the proximity effect and Lorentz forces between the parallel coil windings are observed. This work attempts to investigate the mechanical consequences of these phenomena using numerical and experimental methods. A numerical model was developed in LS-DYNA. It was validated using experimental post-mortem strain and laser-based velocity measurements after and during the experiments, respectively. It was observed that the proximity effect in the parallel conductors led to current density localization at the closest or furthest ends of the conductor cross-section and high local curvature of the formed sheet. Further analysis of the forces between two coil windings explained the departure from the “inverse-distance” rule observed in the literature. Finally, some measures to prevent or reduce undesired coil deformation are provided.

The Numerical Analysis of Force and Comparison of Pulse Magnet and Electromagnetic Forming Coil

“…The high-strength magnetic field generated by the coil interacts with the current in the conductor to generate a huge electromagnetic force. The coil works in a magnetic field of more than 20 T for a long time, and the material gradually deforms to cause a rupture [4]. The strength of the coil is affected by its structure, material, and manufacturing process.…”

Impulse-Based Manufacturing Technologies

“…Goyal et al present fundamental results regarding the mechanical loads acting on the coil. They consider skin and proximity effects to numerically calculate the current density distribution and the resulting deformation of the coil winding as a function of the arrangement of the individual winding turns relative to each other and the workpiece [7]. As a supplement, Beckschwarte et al examined the molding tools.…”