The effect of active and passive third body film in friction of carbons Part 1: Friction and wear performance at various scales

Abstract

In the friction of carbon materials, it has been found that the coefficient of friction is dependent on the total energy absorbed by a given mass and the rate at which the energy is dissipated. Usually, low energy absorption and low rate of energy dissipation produces relatively high coefficients of friction. Conversely, high energy absorption and high rate of energy dissipation leads to lower coefficients of friction. In addition, testing at low energy input in a moist environment produces a low coefficient of friction, which may increase significantly during the course of the test. Similar friction transitions occur during high energy tests. However, these do not appear related to moisture effects. In some higher velocity tests, very high local temperatures were detected even though the bulk temperature rise is relatively low. The scope of this paper focuses on the transient changes of friction coefficient and the hot spotting phenomena. The tests were conducted using both pin-on-disk and disk-on-disk setups. Although test scales were different in both tests, a very good match in results was found.