Mode of zero wear in mechanical systems with dry contact

A theoretical and experimental analysis of a mechanical system with dry contact and subject to harmonic excitation is made. The adopted model is a two-degree-of-freedom system representing two sub-structures in dry contacts from their flat ground surfaces. It is theoretically shown that the two sub-structures move in phase with equal amplitudes at a particular frequency of oscillation. This particular frequency is called the frequency of virtual sticking and depends upon the physical properties of the two contacting sub-structures as well as the ratio between the amplitudes of external forces applied on these two structures in the direction of their friction sliding. Zero wear of contact surfaces can thus be established since relative velocity between encountered asperities of sub-structure surfaces becomes zero. It is shown, theoretically and experimentally, that when one of the applied harmonic forces is zero, the frequency of virtual sticking is equal to the natural frequency of the unforced sub-structure. The displacement ratio of the two contacting structures under the effect of harmonic excitation in their sliding direction is investigated within a frequency range up to 400 Hz. The tangential contact stiffness and the dynamic contact rigidity are theoretically determined and experimentally predicted from the measured forced displacement ratio.