Failure of Cu Rolling Triboelectric Pairs under Various Load and Voltage

Rolling electric contact is a novel style of conducting rotary joint, whose failure behavior and the involved mechanism under triboelectric conditions are studied by FTM-CF100 tribometer. It is found that the friction coefficient keeps stable firstly and then grows up as rolling continued, at the same time, the current rises rapidly at initial then level off. And the friction coefficient and current lose their stability during the rolling. After rolling for at least 180 minutes, the final friction coefficient and current increases with the increasing of contact load under a constant voltage. Load increasing can improve the stability of triboelectric contact.Moreover, the friction coefficient and its fluctuation increase with the growth of voltage, which is always higher than those during mechanical rolling. The performance failure could be summarized as significant rising of friction coefficient and deterioration of current stability. The growth of load and voltage will accelerate failure process. Based on micro characterization, it is speculated that asperities on triboelectric pairs should be flatten more easily due to the mechanical stress and joule heating, resulting in lower roughness and larger contact area, and consequently leading to the rising of current. The friction coefficient increases because of the adhesion between the asperities. The deterioration of triboelectric contact stability could be mainly attributed to the local oxidation and oxides debris.