| Current-carrying frictional pairs, namely sliding or rolling contact pairs providing current-carrying capability, which are widely applied in fields of transportations, electric power and weak electric control. As technology being quickly developed, tranditonal techniques could not meet the demands of these increasingly harsh conditions, which have seriously restricted the development of such fields.In this doctoral thesis, the triboelectric behaviors of copper-based material were investigated. The pure copper, copper-base powder metallurgy materials used in electric pantograph and Cu-impregnation carbon materials are selected as pin samples, and the QCr0.5 is used as disk samples. The tribological tests are carried out on the homemade HST-100 high speed tribometer with electrical current.The results reveal that there are strong coupling effects between the tribological behaviors and the electrical behaviors for the current-carrying frictional pairs. For example, the tribological properties become worse with the appearance of electricity, and the wear rate increases as the electricity increases. At the same time, the unstability of frictional contact can cause the deterioration of current-carrying quality. And the more unstable the tribological conditions are, the poorer the current-carrying quality becomes. The regression analysis of wear rate and current-carrying efficiency reveals that the velocity, electricity and the load play coupling but different roles on the triboelectric behaviors. The results also suggest that there is a certain relationship between dynamic friction coefficient and dynamic electricity.The associated arc in the current-carrying friction is also investigated. The arc appears on the friction surfaces and the lifetime can last for only several milliseconds or less. The process of arcing can be divided into generation, growth and dissolve, which shows the characters of randomness and dynamics. Specifically, the randomness is expressed in arcing place, arc duration and intensity of arc. The dynamics behavior is expressed in movement along the direction of friction, the progress and the fluctuation of arc intensity. It is found that these characters of arc have certain influences on the vibration of material damage and current-carrying quality.The research on the failure mechanism shows that the damge of material and the deterioration of current-carrying are inhomogeneous on the whole surface, and they interact with each other. Besides the damages involved in uausal dry sliding friction, electricity can cause some new destruction forms, such as sharp temperature increasrising of frictional surface, serious oxidation of material, increasing of metal plastic flow on surface and subsurface, roughening of the surface and melting and splattering induced by arc. Moreover, it is noted that the triboelectric behaviors are ununiform along the sliding direction on the pin sample. For example, the electrical damage is more serious near the exit direction of the friction surface, while the mechanical damage dominates the wear near the entrance direction of the friction surface. Meanwhile, the dominated conduction mode is contact conduction near the entrance and is arc conduction near the exit, respectively. The mechanical damges and contact conduction will decrease but electrical damage and arc conduction will increase when electrical and frictional contact conditions worsen.According to above research, to make both tribological behaviors and electrical performances better, it is necessary to improve conductive contact and frictional contact together. Novel Cu-graphite composites is developed to try to solve this problem. It is found that a continued-spontaneous-conductive-lubricous surface film can form during the current-carrying sliding, which could improve the stability of the contact and inhibit the generation of the arc, and consequently improve the current-carrying tribological performances.The results on the coupling relation between tribological behaviors and electrical performances could provide useful guidelines to inhibit the arc damage, and the development of Cu-graphite composites will encourage the progress of material selection for the triboelectric pairs. |
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