Modelling of magneto-electro-thermo-mechanical coupled behavior of the lubricating liquid film for the electromagnetic launch

The electromagnetic launch structure can convert the electromagnetic energy into kinetic energy at high-power level. To improve the energy conversion efficiency, it is critical to maintain the sliding contact between the armature and rail structure under the strong pulse current. However, the high-velocity sliding contact accompanied by the high-density current generates large amounts of the frictional heat and joule heat, which will lead to the high temperature melting of the interface material. To reduce melting damage of the contact interface and improve the reliability of the launch structure, the lubrication with liquid metal is considered in this paper. Based on the lubrication theory and the theoretical framework for the strong coupling of electromagnetic field, temperature field and elastic stress field, a magneto-electro-thermo-mechanical coupled model for the lubricating liquid film is proposed by solving the governing equation with finite difference method and finite element method. The proposed model is verified by comparison with the previous results at the specific conditions. It is shown that the proposed multi-field coupling model could better describe the flow characteristic and thermal parameters of the liquid film under different liquid thicknesses because of the consideration of a more suitable thermal boundary conditions. Especially, the results show the temperature reduction ratio can reach up to 48% for the armature contact surface and up to 25% for the armature interior. These results will be significant to understand the lubrication with liquid metal under the pulse current and facilitate the durable design for the electromagnetic launcher.