Improving Start-Up Contact Distribution Between Railgun Armature and Rails

Contact pressure between the armature and rails of a railgun is critical to rail lifetime, armature acceleration, and consistent shot behavior. A zero-velocity contact is provided by the mechanical strain of the armature flange in interference with the rails. The contacting surfaces of the armature typically have unpredictable, localized concentrations of contact pressure and areas with no contact pressure at all. A method to improve contact distribution and maintain control of the total contact force magnitude is introduced in this paper. This technique, called the predicted displacement method (PDM), showed promising results on simple model geometries and successfully demonstrated its ability to improve the design of a solid C-shaped railgun armature. The simulation results also illustrated the PDM's ability to scale contact force magnitude while preserving the improved pressure distribution.