Comparative analysis of the influence of coil geometry on the electromagnetic formability of the AA1100 sheet: An experimental and numerical modelling

Electromagnetic forming is a non-contact, high-speed metal-forming process in which the Lorentz force is responsible for the deformation of the workpiece. The coil's geometry and dimensions used to generate magnetic pressure play an important role in the sheet's uniform deformation. The novelty of this work is to investigate the effect of novel coil geometries, namely circular spiral coils (CSC) and rectangular spiral coils (RSC), on the formability of a 0.8 mm-thick AA1100 workpiece under electromagnetic forming (EMF). The coils used in the EMF process have identical spacing, equal numbers of turns, and a constant cross-sectional area. Experimental trials were performed by gradually increasing the discharge voltage and energy to the workpiece's fracture limit. In addition, numerical simulations were performed using the LS-DYNA solver. Formability, in terms of dome height, of the deformed workpiece was compared between experimental and numerical analyses. Some additional important parameters for the coils and the workpiece were analyzed, including current density, magnetic field, and Lorentz force density, as well as structural parameters, such as effective plastic strain and von Mises stress, developed in the workpiece. Experimental and numerical analysis results at a 10.05 kV discharge voltage reveal that the formability of the workpiece is higher in RSC than in CSC by 29% and 32%, respectively. However, the CSC demonstrates a more uniform material flow and magnetic field distribution. This research provides critical insights into how coil geometry influences high-strain-rate forming, establishing it as a primary factor in determining forming performance.