Study on the Distribution of Deposition Layer on the Rail Surface and Its Influence on the Armature Start-up in Railgun

Deposition occurs on the rail surface during the start-up stage of the launching process. These phenomenon influence the velocity of the armature, the acceleration of the armature and the launching stability of the launcher. In this article, 15 experiments with the linear current density of 19 kA/mm were carried out. The morphology of the rail surface at the armature start-up stage and the start-up time of the armature were measured by a 3-D laser profilometer and a high-speed camera, respectively. Three conclusions are obtained: 1) the morphology of the deposition layer on the surface of rails is high at the edges of armature-rail interface and low in the middle of interface because of nonuniform contact pressure and temperature; 2) as the number of experiments increases, the thickness of the deposition layer on the rail surface increases and then tends to stabilize; and 3) the start-up time of the armature increases rapidly, and then tends to stabilize. Moreover, to analyze the reason for the distribution of deposition layer on the rail surface observed during start-up stage in experiments, the contact pressure, current density and Joule heating were calculated. Results show that the contact pressure of the edges of the armature is relatively high, and these areas are also where high temperature is concentrated on the surface of the armature.