Sliding Characteristics in the Copper Contacts
Faculty of Engineering, Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-91, Japan
A low rotational frequency sliding tester which could measure electrical contact resistance and coefficient of friction simultaneously was trially fabricated. Relations between electrical contact resistance and coefficients of friction were investigated by making sliding test on clean copper and surface oxidized copper contacts respectively, which were used relatively frequently in industries. As far as the measurement work made this time, of which rotational frequency was low, was concerned, it was found that the heat generation due to mechanical friction was low and the heat generation due to Joule’s heat in the case of sliding clean contact surfaces was also low because of low contact resistance. It was, however, found that CU²0, etc. were formed due to rapid progress of oxidation by the generation of Joule’s heat at the contact surfaces, of which real contact areas were extremely small, being roughened along with the increase of the sliding frequency. On the other hand, it was further found that although the existence of oxides in advance at the sliding surface extremely lowered the coefficient of friction (0.07 for example) in which the oxidized film indicating contrarily (70mΩ for example). It was presumed that formations and destroys of oxidation film were repeated by flow of electric current at the contact spot to cause Fritting Phenomenon.