Study On The Armature-rail Structure Dynamics And Hypervelocity Gouging Of Electromagnetic Railgun

The electromagnetic railgun(EMRG)uses the huge electromagnetic thrust produced by immense pulse current to accelerate the projectile to a hypersonic speed,and has an obvious superiority compared with the traditional chemical emission technology,so it has a wide application prospect in the military.The sliding electrical contact at a large current and a high-speed between the solid armature and rails in EMRG is accompanied by complex physical processes such as friction,wear,ablation and vibration.The phenomenon of gouging at high speed in railguns seriously shortens the service life of the conducting rails,and therefore restricts the engineering application of railguns.This paper focus on the scientific problems about the armature-rail structural dynamics and the damage caused by hypervelocity gouging in solid armature railguns.The research has been carried out from the aspects of experiment and theoretical simulations.The main works are as follows:(1)A detachable medium caliber electromagnetic launch experiment device was constructed,and the launch experiments with the muzzle velocity above 2.0km/s were carried out.The dynamic erosion and wear of the armature and the internal ballistic process were simulated based on the electric,thermal and force multi fields effects during the launching process,and considering the factors such as contact interface erosion,friction,nonlinear electrical contact and aerodynamic drag.The simulation results were compared and analyzed with the residual aluminum deposited on the surface of the conducting rails.The phenomena and laws of the hypervelocity gouging on the conducting rails were analyzed and summarized.In addition,the optimization of the armature feed position of a rectangular caliber launcher was generally derived and analyzed.(2)The rail under the distributed electromagnetic force was simplified as the Bernoulli Euler beam model,and the vibration control equations were solved by separation of variables.The analytical solutions of the vibration of the conducting rails without damping and with damping under time varying current were derived.The dynamic responses of the armature-rail structure under these conditions were calculated and analyzed respectively:the armature moves at constant speed,the armature accelerates under a typical current,the rail structure with damping effect.The critical velocity effect of dynamic responses was clarified.Based on the 3D dynamics finite element simulation,the lateral overload and dynamic response characteristics of the integrated launch package(ILP)during launching were analyzed.Furthermore,the feasibility of improving the dynamic response of the rails with non-uniform stiffness support structure was preliminarily discussed.(3)Based on the structural characteristics of railguns and the theory of impact thermal dynamics,the calculation model of railgun gouging was established by explicit dynamic finite element method and material point method respectively.The 3D mechanical-thermal coupling numerical simulations of the forming process of the railgun gouging were carried out,and the evolution process and the physical mechanism of gouging were described and analyzed.The formation mechanism of railgun gouging is summarized into two kinds:one is the parallel impact between armature and guide rail induced by the uneven surface of the guide rail;the other is the small angle oblique impact of armature and rail surface caused by the lateral oscillation of armature motion.(4)Based on the compression shock wave theory and material Hugoniot equation,combined with a lot of experimental data of gouging,a formula for predicting the threshold speed of gouging is introduced,which can be used to guide the material design for anti gouging.The analysis shows that the armature and rail materials with small impact impedance and high surface hardness can increase the threshold velocity of gouging.Based on the 3D numerical simulations,the influence of velocity,material and structure on gouging damage was studied and analyzed.Finally,the influence of different copper alloy rail cladding materials and different pretightening conditions on gouging performance was studied through experiments,and the restraining method of railgun gouging is preliminarily verified.In this paper,through the study of the friction and wear of electric contact ablation,the dynamic response between the ILP and the rails and the phenomenon of hypervelocity gouging between the armature and rails of the EMRG,some conclusions with theoretical and engineering application value have been obtained,which is of certain significance for the life enhancement and engineering application of the EMRG.