Studies On The Influence Of Armature’s Vibration Characteristics On Electrical Contact Between Armature-rail Interface

Electromagnetic railguns utilize Ampere force to accelerate projectiles to ultra-speed,whose maximum velocity can be several times and even higher than artillery’s.Armature in railguns is an indispensable component of transforming electric power to mechanical energy,and several requirements like withstanding conditions of mega-ampere current,ton-force,20 Tesla magnetic field and accelerating projectiles must be met.High-speed sliding electrical contact between the armature-rail interface could induce transition and vibration of armature or gouging and central wear of rail.Studying the high-speed sliding electrical contact between the armature-rail interface and ensuring adequate electrical contact between the armature-rail interface is significant for improving the performance of electrical contact,avoiding transition during the launch,obtaining anticipated launch test results and is beneficial for further practical development of electromagnetic launch technology.It’s commonly supposed that transition is caused by the lack of mechanical contact pressure or electromagnetic contact pressure.Yet the tail part of an armature can vibrate or bounce on uneven surface of rail which could affect the performance of electrical contact,destroy contact status of the armature-rail interface and even generate transition arc.Method of the electromagnetic launch finite element simulation is adopted in this paper to study the effect of armature’s vibration characteristics on electrical contact between the armature-rail interface.Besides,armature-rail finite element simulation model is established based on the method to study the dynamic characteristics of rail under various conditions.Based on the results of dynamic simulation of rail,a single-degree vibration model of armature is created for studying the influence of asymmetric wear and different launch conditions on armature’s vibration characteristics,and the method of suppressing vibration of armature and improving the performance of electrical contact between the armature-rail interface is proposed in this paper.Two-dimension rail vibration finite element simulation model and rail vibration model of a beam on an elastic foundation is established based on the launcher with the caliber of 50mm×60mm,and dynamic simulation of rail under different load conditions is carried out with the help of the multi-physics finite element simulation software ANSYS.Based on the results of the simulation above,a single-degree free vibration model of armature is created for modal analysis,and a single-degree nonlinear vibro-impact model is established using Hertz contact theory.With the two models above,vibration curve of armature in one vibro-impact cycle is plotted by numeral calculations.Based on the single-degree nonlinear vibro-impact model,research of the effect of armature’s velocity,electromagnetic force,structure of armature and asymmetric wear on armature’s vibration characteristics is carried out.Last but not least,launch test is conducted to verify the influence of thickness of armature’s shoulder on electrical contact between armature-rail interface.Vibration mechanism of armature caused by rail deformation under the impact of elastic waves is proposed in this paper,and single-degree free vibration and nonlinear vibro-impact models are built for numeral calculations.By means of theory analysis,numeral calculation and experimental verification,method of improving the performance of electrical contact between the armature-rail interface,decreasing the probabilities of transition and improving the efficiency of launch test is obtained in this paper.