中文摘要：

增加或保障电枢与轨道具有较大接触面是电磁轨道炮设计与试验中的一个重要目标，但实际上接触面大小的作用仍有待探讨。为此，通过仿真计算分析了接触面上电流分布区域的位置与电流大小。结果表明：电流仅从小部分接触面穿过，在满足该接触面大小的情况下，接触面再增加或接触面大小对轨道电枢接触的电磁性能影响不大；同时，电流流过的区域大小与电枢和轨道的尺寸以及电流随时间的变化有关。对被分析的结构，在电流平顶阶段，接触面积为电枢侧面的20％（接触面长度约为8mm，实际接触面大小约为240mm2）已可认为足够大，接触面再加大最大电流密度己基本不变。因此，在固定尺寸的电磁轨道炮中，不必过分追求大电枢／轨道接触面，保证一个接触面大小满足电接触的电气性能即可。

英文摘要：

A main goal in the design and operation of railguns is to make a larger contact area between the armature and rails. However, it is not necessary to make a very large one, since the current only flows on the part of the contact area from the rail to the armature, and the other part is almost useless. By simulating, we analyzed the location and the size of the area where current flows. The results show that current only flows through a small contact area, and after meeting the requirements of the contact area, the size of the contact area has little influence on electromagnetic behavior of the railgun. The size of area that current flows depends on the structure of the armature and rails as well as the time-varying characte- ristic of the existing current. For the certain structure with U-shape armature analyzed in this paper, the contact area is about 20% of the whole armature flank surface（the length of the contact area is about 8 mm, the actual contact area is about 240 mm2）, and the maximum current density keeps almost the same for larger contact areas.