Failure analysis of pulse magnetic induction coil in electromagnetic riveting

Abstract

Pulse magnetic induction coil is the core component of electromagnetic riveting (EMR) equipment. Due to the multi-field coupling working environment, it was easy to fail. In this paper, multi-field coupled simulation was carried out to analyze the failure of pulse magnetic induction coil. The current, riveting force and damaged condition in experiment results demonstrated that the model was accurate and reliable. The simulation results showed that the current density was higher at the middle turns because of the eddy current. The Lorentz force, whose radial components concentrated in inner turns and axial components in middle turns, were unevenly distributed. The Lorentz force led to uneven deformation and this nonuniformity of stress deteriorated with the increase of the discharging voltage. The first turn of the coil suffered from greater stress and is more prone to deformation. Besides the Lorentz force, the higher temperature in the center of the coil also accelerated the breakdown of the insulator. In respect of the issues above, a new type of tower coil was proposed to improve the uneven distribution of Lorentz forces and stresses. The simulation results showed that the maximum stress of the coil decreases obviously under the same riveting force.