3D TRANSIENT SIMULATION OF MELT WAVE AND TRANSITION MECHANISMS IN A MOVING ARMATURE

The A, phi-A finite element method (FEM) is employed to calculate the 3D transient eddy current field and temperature field in a railgun with a moving armature based on a Lagrange coordinate system. It is assumed that the element's material properties are changed from metal to air when it is melted. Simulation results show that this model can greatly simulate the influence of current distribution by velocity skin effects. It predicts a current density concentration on the tail and side edge of the armature where the temperature is higher. Also the melt wave diffusion process can be described from the tip of the tail to the center. At the same time, the frictional heat is cumulative on the surface and leads the surface melting more quickly and the melt wave moving faster than the solid state. When the armature surface has completely melted into a gaseous phase a transition occurs. This melting transition mechanism is simulated and discussed meticulously.