Importance of electrical and physical contact in electromagnetic forming simulations

In both industry and academia, researchers often use numerical simulations to reduce the number of trial-and-error iterations required in experiments to reduce costs. However, this can be difficult in the EMF process where electricity is flowing with relative motion between the workpiece and conductor. Thus, a coupled electromagnetism (EM)-structural analysis, which also includes EM contact, has to be conducted. In this paper, in order to further understand the science behind the EMF process and benefits of a coupled numerical analysis, a numerical model was created in a commercial software package, LS-DYNA, for a coil design called a uniform pressure actuator (UPA). Numerically predicted workpiece velocities and displacements were compared with those in experimental tests measured using a Photon Doppler Velocimetry (PDV) and Coordinate Measurement Machine (CMM). Simulations of idealized electrical conditions without material draw-in as well as more physically accurate simulations where EM contact allowed material draw-in were conducted. The inclusion of material draw-in allowed more accurate predictions of experimental displacements and velocities. In addition, the fact that shear stresses in the formed wall cause the inverse saddle geometry of components produced with a UPA is shown.