During the electromagnetic launch process, there is a contact surface between the trailing arm of C-shaped armature and the rail. This contact is generally provided by the deformation of the trailing arm, from which can keep a good metal-metal contact at the armature-rail interface, while providing sufficient contact force to ensure the launch without transition. Nowadays C-shaped armatures with curved surface trailing arms have been used in rectangular bore railguns. In this paper, the effect of geometry change on the curve shape is investigated. Various kinds of reasonable curve shapes are explored and simulated by using finite element method. Contact area, contact pressure and contact force of C-shaped armature with different curve shape are calculated and compared respectively. Eventually, the variation laws of contact characteristics at the armature-rail interface with different kinds of curve shapes are acquired. 2-D and 3-D simulations are both carried out and the simulation results are quite consistent with each other.
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