Effects of contact pressure concentrations in rail/armature surface at startup of a railgun launch

During the early portion of a railgun launch, the magnetic pressure is too low to provide the sufficient loading of the contact faces, thus an interference fit between the trailing arms of the armature and the rails is designed to provide initial mechanical pressure to keep the contacts in compression until the current has risen to the point where the magnetic forces supply the required loading. Because insufficient initial pressure would result in contact separation of armature and rail, it is believed that a slight larger contact force can be more effective to eliminate the occurrence of an arc at the start-up of the railgun launch. However, interference fit between the rails and the armature always causes some deformation of the armature, which may result in some undesirable effects. This paper focuses on the phenomenon of contact pressure concentration caused by interference fit in the contact surface of the armature. The effects of this kind of contact pressure concentration on the current distribution and the formation of armature surface erosion wave are studied. The current concentration patterns caused by rapid increase of driven current and contact pressure concentration are examined. The dependence of the pressure concentration on the armature structure parameters is investigated.