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Electromechanical Performance of Rails With Different Cross-Sectional Shapes in Railgun

Railgun is a kind of electromagnetic launcher that can accelerate masses in the range from milligrams to tens of kilograms to velocities more than several kilometers per second. The cross-sectional area's moment of inertia is one of the most important mechanical properties of the rails, affecting the critical velocity and launch performance. The current distribution in the railgun determines its efficiency and contact performance of rail/armature sliding. Factors that affect the electromechanical performance of the rails include geometry and material. To improve the electromechanical performance, two types of rails with convex and concave cross sections are designed by adding and removing arch forms to/from the conventional flat rails. Modified C-shaped armatures are constructed for each rail geometry. This paper presents the results on mechanical performance on the basis of structural analysis and current distribution from coupled EM-structural simulations. The results show that the moments of inertia of convex and concave rails are larger than those of flat rails for a given cross-sectional area and rail width, but the differences in mechanical performance among the three geometries are not significant, and the advantage of rails with larger moments of inertia for a given cross-sectional area is limited. The inductance gradient of the flat railgun is larger than those of the others, and the concave railgun has the smallest; consequently, the concave railgun is the least efficient. Compared with the flat and concave rails, the current density of the convex rail is smaller at the bore-side rail surface, but greater at the contact interface, especially at the trailing edge of the armature.