复合型电磁发射轨道接触应力分析

Contact Stress Analysis of Composite Launching Electromagnetic Rails

电磁轨道发射时,电枢在轨道内滑动,轨道内表面与电枢之间会产生高温和摩擦,轨道将受到磨损、烧蚀及强度等破坏.因此,人们开始考虑采用铜基复合轨道来增强轨道内表面的强度及耐烧蚀能力.该文研究的是以钢材料作为复合层的铜基复合电磁轨道.当轨道通入电流时电枢与两轨道组成闭合回路,两轨道间形成强的磁场,电枢在磁场的作用下受到推力并沿着轨道移动.在这个过程中由于电流和磁场的相互作用,轨道间会产生相互作用的斥力;同时电枢在强电流的作用下产生大量的Joule(焦耳)热使得电枢产生膨胀,对两轨道的侧面造成挤压,根据轨道的受力情况将复合型轨道简化为受有一段均布载荷和一个"刚印"作用下的双层梁的力学模型.根据弹性半平面的基本方程求解电枢对轨道表面局部的作用力,进而得到整个轨道的复合层的应力状态;然后利用MATLAB软件对铜-钢界面上的应力进行多项式拟合,得到铜层表面的边界条件,分析铜层表面局部的各项应力,得到了复合轨道基层和复合层的应力与加载电压、复合层厚度比例等参量的关系.为复合型轨道的强度设计提供了依据.

During the launching process of electromagnetic rails,the armature slides along the rails,and high-temperature friction occurs on the rail-armature interface,so the rail is liable to damages due to wear,erosion and strength loss. Thus,copper-based composite materials are used to enhance the strength and ablation resistance of the inner surface of the rail. The steel-copper composite electromagnetic rails were studied. While electrified,the armature and the rails constituted a closed loop,and a strong magnetic field formed between the rails,then the armature moved along the rails under the pushing force from the magnetic field. In this process,due to the interaction between the current and the magnetic field,a repulsive force acted between the 2 rails. At the same time,the armature was greatly heated by the strong current,and the thermal expansion of the armature brought extrusive forces on the lateral rails. According to this force condition,the composite rails were simplified as a mechanical model of double-layer beams under a uniformly distributed load and a rigid stamp force. The forces by the armature on the rail surface were solved and the stress state of the composite layers was obtained with the basic equations in the elastic half plane. Hence,the polynomial fitting of the copper-steel interfacial stress was got with the MATLAB software. The boundary conditions of the copper layer surface were determined,the local stresses of the copper layer surface were analyzed,and the relationships between the stress and the loading voltage,as well as the thickness ratios of composite layers,were acquired. The results provide a foundation for the strength design of composite launching electromagnetic rails.