Abstrakt: |
The results of experiments continuing the study of the features of the temperature effect on the frictional characteristics of metal friction pairs are presented. The features lie in the ambiguity of this effect associated with the prehistory of the contact, that is, with the sequence of temperature changes that preceded this state. The object of research is a friction pair of gold and gold–copper alloy (80% Au, 20% Cu). The following temperature effects are investigated experimentally during the heating of the contact from room temperature to the maximum temperature and cooling of the contact from the maximum temperature to room temperature: the temperature effect on the maximum force of static friction, on the coefficients of static Amontons and Coulomb friction, and on the specific force of static friction. The experiments are carried out according to the ball–plane friction scheme: a spherical sample with a radius of curvature of 0.5 mm made of the Au80Cu20 alloy was in contact with a flat sample of gold (Au99.99). Normal contact load varied in the range of 0.5–4 mN, and the temperature varied in the range of 21–130°C. It is shown that the experimental dependence of the friction force on the normal force in contact is adequately described by linear regression equations: single-term (Amontons' law) and binomial (Coulomb's law). The coefficients of linear regression models (Amontons and Coulomb friction coefficients) are statistically significant at p = 0.05, and, at the same time, they are independent of the normal load. The values of the proportionality coefficients (friction coefficients) in the binomial regression dependence of the friction force on the normal force are on average 12% less than the analogous coefficients in the single-term regression dependence. The nature of the temperature dependences of the static friction forces and the Amontons and Coulomb friction coefficients sensibly coincides with heating and cooling of the contact; hysteresis does not appear in these dependences. The results are of theoretical and practical importance for improving the quality and reliability of sliding electrical contacts that are heated as a result of Joule heat. [ABSTRACT FROM AUTHOR] |