Experimental Study of Armature Melt Wear in Solid Armature Railgun

Transition is an important issue in rail electromagnetic launches; it limits the performance of electromagnetic launch systems. In launch progresses, wear on the contact surface of armature significantly affects the contact surface morphology and armature structure. Studying wear, contact resistance, and sliding friction coefficient of the contact surface between the armature and the rail is important to understand and suppress transitions. In this paper, specially designed armatures, which make the wear on armature contact surface all melt wear, are used in rail launch experiments, to measure the wear rate of melt wear and observe how it is affect by loading. In the experimental results, average wear rate is represented by the average thickness of aluminum debris left on the rails: the average wear rate is within 0.6-2 mm/m and the average debris thickness is in a range of 3-10 μm . Based on the idea that melt wearing is the main mechanism, the heat balance of contact surface is analyzed. It is concluded that melt wear absorbs much of the heat generated in the surface, and the remainder goes into the rails. Equations based on this heat balance based are then derived to establish relationship among melt wear, launch parameters, and material parameters. According to the equations and the experimental results, the contact resistance of armatures with 80 mm² contact areas is 2.56 μΩ, the contact resistance of armatures with 50 mm² contact areas is 4.09 μΩ and the sliding friction coefficient is 0.11.