电磁轨道炮试验过程中枢轨界面的接触电阻特性

Contact Resistance Characteristics of the Interface Between Armature and Rail in Electromagnetic Railgun Launching Tests

电磁轨道炮枢轨界面的接触电阻对界面热量和轨道炮系统的性能有着重要影响。为了计算轨道炮发射过程中的接触电阻,构建了发射过程电路模型,结合试验数据得到了接触电阻的数值和曲线。首先利用构建的发射过程电路模型确定了回路阻抗表达式。然后结合试验测量的炮口电压、炮尾电压和轨道电流,拟合了电枢的位移曲线和速度曲线。最后利用MATLAB进行数值计算,得到了轨道炮发射过程的回路阻抗和接触电阻数值,以及在轨道裸露和覆有铝熔膜2种情况下接触电阻的变化曲线。通过分析接触电阻的变化特性,得到了以下结论:在发射过程中,回路阻抗在一定范围内震荡,接触电阻则随电枢前进呈现不断减小的趋势;轨道表面的粗糙化和黑色氧化物减少了枢轨间固-固接触的实际面积,增大了接触电阻;而覆盖轨道的铝熔膜能增大实际接触面积,减小接触电阻。

For an electromagnetic（EM） railgun system, contact resistance of the interface between armature and rail has a significant effect on the interface heat and the railgun performance. To calculate the contact resistance during launch, we established a circuit model for railgun. Combining with test data, we obtained the value and waveform of contact resistance evolvement. Moreover, the expression of loop impedance was determined according to the circuit model. Then, by taking the experimentally measured breech voltage, muzzle voltage, and rail current into consideration, the displacement curve and speed curve for armature were fitted; numerical calculation was carried out in MATLAB to obtain the values of loop impedance and contact resistance during launches; thereby, the waveforms of contact resistance under two contact conditions-bare and aluminum melt film covered- were also acquired. By analyzing the characteristics of contact resistance, following conclusions are drawn： during launch process, loop impedance oscillates in a certain range, and contact resistance gradually decreases along with armature sliding ahead; surface roughening and black oxide on rail decrease actual contact area and increase contact resistance; aluminum melt film covered on rail contact surface can increase actual contact area and decrease contact resistance.