Coupled Mechanical and Electromagnetic Analysis of Current on Armature and Rail Interface With Dynamic Contact

Abstract

The electrical contact between the armature and rail (A/R) in a railgun is acknowledged as a dynamic sliding interface, exhibiting properties distinct from bulk. This paper employs a 3-D finite element method (FEM) for coupled mechanical and electromagnetic analysis and proposes boundary conditions for dynamic sliding contact to investigate current distribution on the A/R interface. Results show that contact pressure and area have similar trends as the driving current, which confines current distributed areas. The current distributions on stationary and sliding interfaces reveal different patterns but the distributed areas both locate within the contact areas. In the case of the stationary scenario, the current concentrates at the trailing edge when the current increases and diffuses to the leading edge when the current declines. However, due to the velocity skin effect (VSE), the current fails to diffuse into the interior during all stages. Besides, comparative calculations with constant contact indicate that forced shifts of current occur when the contact is dynamic, dominating the current distributions of the A/R interface. Moreover, the influence of the VSE on forced shifts of current is notable, with significant current variations observed near the trailing edge, whereas those around the leading edge are less pronounced.