Kinetic friction coefficient measured in tribotesting: Influence of frictional vibration

Using a novel anti-vibration tribometer with a yaw angle misalignment, Kado et al. (Trans. Jpn. Soc. Mech. Eng. C79: 2635-2643, 2013) have recently shown experimentally that frictional vibration in tribotesting causes considerable error, e.g., a 35% underestimation of the kinetic friction coefficient for the sliding contact between a steel ball and a steel plate lubricated with glycerol. In this paper, it is shown that their experimental results can be numerically simulated based on a purely mechanical model, which confirms that their experiments were earned out properly and also that in conventional tribotesting, the measured kinetic friction coefficient (obtained from the time-averaged spring force) is not the inherent kinetic friction coefficient (determined by the inherent nature of materials in contact as a function of the relative velocity) but the effective kinetic friction coefficient (determined by the mean energy consumption rate as a function of the driving velocity). The effective kinetic friction coefficient depends on the mechanical properties of the tribometer used in the test, and it corresponds to the inherent kinetic friction coefficient when the measurement is carried out with no frictional vibration. Copyright © 2014 Japanese Society of Tribologists.