Investigations on non-uniform coefficients of magnetic pressure distribution in railguns

In the process of electromagnetic launching, the nonuniform contact pressure distribution on the armature-rail interface keeps changing with the armature moving on. At first, the contact pressure is mainly provided by the deformation of the trailing arm, from which it can keep a good metal-metal contact at the armature-rail interface. After the pulse current is constructed, the magnetic pressure will dominate the contact pressure because it is much larger than the mechanical interference pressure. In this paper, the 3-D modeling of magnetic pressure distribution is carried out with finite element method. In the simulation of 3-D contact calculations, the situation that current enters armature from the trailing edge is selected for using here. The electromagnetic force perpendicular to armature trailing arm is equivalent to uniform load on the inner surface of trailing arm. Typical contour pattern of non-uniform magnetic pressure distribution is acquired. Some nonuniform coefficients of magnetic pressure distribution are proposed and analyzed to evaluate the contact performances between armature and rails. A series of simulations are conducted under the conditions of different magnitudes of magnetic pressure, also with different armature structure parameters. The characteristics of the non-uniform coefficients are investigated and discussed. Dependences of the non-uniform coefficients on equivalent uniform load and armature structure parameters are obtained.