电流负载对滑动电接触系统摩擦学行为的影响

To study the effect of current load on the tribological behavior of sliding electrical contact system, and further clarify the relationship between current load and tribological behavior of sliding electrical contact system, a series of tribological tests were carried out on a self-designed friction sliding electrical contact tester. Brass material was used as the rubbing pair, and a ball-on-flat configuration was designed to perform the tests. The brass flat sample with the size of 25 mm×25 mm×4 mm was ground and polished to surface roughness Ra≈0.04 μm. H62 solid brass ball with diameter of 4 mm was selected as the ball sample. During the test process, the DC current loads of 0.2 A, 1 A and 2 A were input to the contact system respectively, then the friction coefficient, friction force and contact voltage signals from the interface were detected and analyzed, and the friction and wear characteristics of the contact surface after test were observed. In addition, the variation characteristics of interface voltage, temperature and shear stress were further analyzed by simulating the test process with thermal-electric-mechanical multi-field coupling algorithm, which was carried out in the finite element analysis software ABAQUS. The test results indicated that when the current increased from 0.2 A to 1 A, there was no significant difference between the friction coefficient and the friction force at the stable stage, and the friction coefficient was kept at 0.5 in the steady stage. When the current load further increased to 2 A, the friction coefficient and friction force increased significantly, the friction coefficient was observed to increase to 0.7. As the current load increased from 0.2 A to 2 A, the contact voltage drop increased gradually from 0.1 V to 0.75 V. It is worth noting that although the current increases by a factor of 10, the contact voltage does not scale up, because the contact resistance of the interface changes with the wear process during triboelectric contact. Therefore, a larger current load causes a higher contact voltage, but the contact voltage does not increase proportionally with the increase of current, because the contact resistance of the interface includes shrinkage resistance and thin film resistance. The wear analysis is performed by optical microscopy and scanning electron microscopy, the corresponding results show that when the current load increases from 0.2 A to 2 A, the degree of interface wear intensifies and the number of wear spots increases significantly, which directly leads to the increase of interface adhesion area, so the friction coefficient and friction force increase significantly. The finite element analysis results further show that when the current increases to 2 A, the interface temperature rises visibly and the thermal effect is significant, so the shear force becomes larger, which further confirms that the wear degree of the interface is aggravated in this state. The results of finite element analysis can well reflect the experimental phenomenon. The results of this study provide a theoretical basis for understanding the relationship between current load and the tribological behavior of sliding electrical contact.