Study on current-carrying friction process based on surface damage evolution

In response to the issues of differences significantly in service stages, performance, and materials used in current-carrying tribo-pairs across different fields. This paper utilizes a self-made micro-sliding current-carrying friction test machine to study the evolution of surface damage during the current-carrying friction process. The results indicate that during all the testing processes, the contact resistance experiences four stages: the smooth surface stage, the transition stage, the optimal friction surface stage, and the failure stage. Variations in load can affect the duration of these stages. The smooth surface stage and optimal friction surface stages exhibit good electrical conductivity properties. The number of cycles during the smooth surface stage decreases with increasing load, reaching a maximum of 518 cycles at a wire diameter of 0.4 mm and a load of 0.025 N. The number of cycles during the optimal friction surface stage increases with increasing load, reaching 9955 cycles at a wire diameter of 1.0 mm and a load of 3.2 N. From the perspective of damage, intense electric arc erosion significantly impacts the current-carrying friction process, and it should be avoided throughout the entire service life of the friction pair. From an engineering perspective, the service stages of "short" lifespan friction pairs such as electrical connectors should correspond to the smooth surface stage. For "long" lifespan friction pairs such as pantograph strips and brushes, the service stages should correspond to the optimal friction surface stage, note that the friction pairs should be run-in.