Tribospectroscopic study of a steel-steel friction couple

The force of friction between a steel plate and a steel sample oscillating at a frequency of 60–70 kHz has been studied as a function of the oscillation amplitude. The static friction force rapidly decays when the oscillation amplitude increases from zero to 0.1 μm. Then, the force decreases only slightly as the amplitude grows further up to about 0.5 μm. The experimental data are interpreted within the framework of a theoretical model comprising two bodies moving in a random potential and coupled by a randomly oscillating bond. An analysis of this model shows that the oscillation amplitude at which the behavior of the friction force exhibits a qualitative change corresponds to a spatial scale producing a maximum contribution to the frictional force. From this, it is concluded that friction in the steel-steel couple originates on a scale of about 50 nm.