Contact Analysis Of Armature-rail Of Electromagnetic Rail Gun In Temperature Field

The analysis of the contact characteristics between the armature and the rail is always an important research field in the technology of electromagnetic rail launch.Although the technology of electromagnetic rail launch is improving,the complex contact state of the armature-rail leads to the transition and the wear of the rail leads to the decrease of the life of the launcher,which is still the key problem restricting the practical application of the electromagnetic rail launcher.Therefore,considering the changes of contact resistance and contact pressure between the armature and rail.In this article,the finite element software was used to conduct the electromagnetic-thermal-stress analysis of the armature and rail,and on this basis to study the friction and wear characteristics,putting forward the feasibility of the electromagnetic thermal crack arrest technology for the self repair ability of the rail with cracks.The main work is as follows:The temperature field and stress field of the contact surface between the armature and the rail are analyzed by finite element software.The change of contact resistance with contact pressure is considered in the calculation process,and the influence of Joule heat and friction heat on the armature and rail damage is studied.It is found that the change trend of contact resistance is negatively related to the change curve of pulse current and contact pressure.The temperature stress and the thermal stress on the rail are distributed in steps,and the maximum value occurs in the initial position of launching;the melting area on the armature surface propagates from the tail edge to the head.In the early stage of launch,the melting of armature is formed rapidly,the melting depth is deepened,and the melting degree of armature is gentle gradually in the later stage of launching.Considering the change of the elastic modulus and hardness of the material with the temperature,the influence of temperature on the wear between the armature and rail is analyzed by using the Archard wear model.It is found that the wear between the armature and rail mainly occurs on the surface of the armature,and the maximum wear is concentrated on the edge area of the armature tail.With the armature moving process,the surface temperature of the contact region increases gradually,the elastic modulus and hardness of the materials in the contact area decrease,and the wear between the armatureand the rail increases.This paper analyzes the formation mechanism of the electromagnetic thermal crack arrest of the rail with cracks,discusses the influence of the different crack tip angle on the rail electrothermal characteristics,and demonstrates the feasibility of the electromagnetic thermal crack arrest technology in improving the track self repair ability.The results show that the temperature rise in the crack tip region is related to the crack angle.When the crack depth and width are fixed,the larger the crack angle is,the smaller the temperature rise is.In the process of pulse discharge,the crack tip is passivated obviously and the curvature of crack tip becomes larger,which effectively avoids the stress concentration at the crack tip and achieves the purpose of crack arrest.