Improvement on formability and forming accuracy in electromagnetic forming of deep-cavity sheet metal part using a dual-coil system

Abstract

A dual-coil electromagnetic forming (EMF) method assisted by radial Lorentz force was proposed herein to achieve the die forming of deep-cavity sheet metal parts. The objective of this study was to certify the extent to which the formability and forming accuracy can be improved by the proposed method. For comparative study, a single-coil EMF system without radial Lorentz force was also utilized. To develop the deformation process, the experiments and simulations of deep-cavity aluminum workpieces under a wide range of voltage combinations were conducted by the single-coil and dual-coil EMF, respectively. The experimental results showed that the dual-coil EMF resulted in the formation of the deep-cavity workpiece with high forming accuracy, maximum die-fitting gap of 0.35 mm, and more uniform thickness distribution. In contrast, the workpiece tended to crack without contacting the die by the single-coil EMF. Based on the simulation results, dynamic deformation behaviors of the deep-cavity workpieces were demonstrated and the underlying mechanisms of the improved formability and forming accuracy were explained. Moreover, the process window of die-fitting gap control indicated that the fittability could be controlled by adjusting the voltage combinations of the dual-coil EMF, and the corresponding optimum voltage of Coil-2 (V2) that contributed to high forming accuracy decreased with the increase of the voltage of Coil-1 (V1). Therefore, the proposed dual-coil EMF exhibits more flexibility and efficiency for producing the deep-cavity sheet metal part with a higher forming accuracy than the single-coil EMF, extending the potential application of the conventional EMF due to the utilization of multiple coils.