Coupled Electromagnetic–Mechanical–Thermal Characteristics and Structure Optimization of Electromagnetically Driven Shaped Liner

Abstract

The studies of characteristics and load configuration of an electromagnetically driven shaped liner during the collapse process are significant for understanding its physical process deeply and guiding its application. A coupled electromagnetic-mechanical–thermal physical model was established and validated for characterizing electromagnetically driven shaped liners. The parameters of the liner structure were optimized for high velocity and strong penetration jet. The outcomes demonstrated that the current and magnetic fields concentrated on the outer surface of the liner at the beginning of loading. Subsequently, they gradually diffused in the thickness direction due to magnetic diffusion. The liner was heated and even ablated by joule heat at current density with several mega-amperes per centimeter. Under a current with a peak value of 4.4 MA and a half-cycle of $1.29~\mu $ s, the diffusion depth of the copper liner is 0.4 mm. Within the diffusion depth, some material near the apex vaporized, while most of the area remained in a solid or liquid state. The collapse velocity increases with decreasing thickness under the same loading conditions. The current density decreases due to the increase in the diameter, and the overall velocity of the liner with a larger cone angle is smaller than that of a smaller cone angle. The tendency and law of the current density, magnetic diffusion depth, and ablation thickness on the loading surface are similar. Furthermore, the ablation near the apex with a larger cone angle is more severe. A shaped liner with a small cone angle is suitable for obtaining a jet with high velocity and strong penetration.