Study of dry friction under small displacements and near-zero sliding velocity

Abstract Many previous works concerning non-lubricated friction have aimed at understanding friction force variations under different conditions (sliding or not) of the interface. It has been found that the static friction coefficient is usually represented as a function of stationary contact time and the kinetic friction coefficient appears to vary with the sliding velocity. This work shows the results of an experimental set-up in which the sliding velocity was kept below 0.2 μm −1 and the displacement of the interface close to 50 μm, thus the previously cited hypothesis is inapplicable. Experiments aimed at clarifying this aspect of the friction problem are described. The results show that the friction coefficient increases in terms of the stationary contact time of the interface and decreases with the sliding distance during the micro-sliding states. These variations are continuous and depend on the displacement history of the interface. They seem to be limited to within two asymptotic boundaries.