Analysis of electromagnetic field generated by a magnetic pulse joining machine

Abstract

In magnetic pulse joining process, the principal components are the massive coil and the workpieces. In the coil-workpiece region, the magnetic field is generated by a pulsed and intense current. The welding is produced by the eddy current in the workpieces. An equivalent electrical scheme is proposed to specify the characteristics of the magnetic pulse generator. The main purpose of this article is to study the propagation of the electromagnetic fields in the coil and its propagation around the coil. The generator is modelled by an RLC circuit. The current pulse is based on experimental measurements using a Rogowski coil and integrated in the numerical simulation as an RLC circuit. Then using magnetic field theory, we measured the magnetic field around the coil using a flux loop and by introducing an analytical model of a massive one turn coil transformed into a multi-turn one. The analytical model is based on mutual inductance between two coaxial circular coils. A 3D numerical simulation using the finite element method and electromagnetic solver in ls-dyna software is developed to calculate the current distribution in the coil. The current density given by numerical analysis shows how the current is insignificant in the outer corners of the massive coil. This approximation is related to the analytical model design by neglecting these corners. Finally, we proposed an experimental setup to estimate electromagnetic fields around the coil. To validate the analytical method and using a massive one turn coil, we performed experimental measurements of magnetic flux density using an external one-turn coil.