Measurement error of kinetic friction coefficient generated by frictional vibration

To measure true values of kinetic friction coefficient in a force balance between the frictional force and spring force, an anti-vibration tribometer (AVT) has been developed. The AVT utilizes a novel principle that an angular misalignment between the two velocities (i.e., the driving velocity of one of contact surfaces and the moving velocity of the other surface) produces a positive damping effect to stabilize the equilibrium point and suppress frictional vibration autonomously. For example, when a sliding contact between a steel ball and a steel plate is lubricated by glycerin, the AVT provides a force balance situation at a misalignment angle φ = 30° (i.e., an anti-vibration setting), although strong frictional vibration occurs at φ = 0° (i.e., a conventional setting). By comparing the kinetic friction coefficients obtained at φ = 0° and 30°, it has been found that frictional vibration can lead to a serious error of measuring kinetic friction coefficient (e.g., a 35% underestimation at a low driving speed).