Mechanism of energy dissipation in mechanical system with dry friction

Determination of the energy dissipative mechanism in a mechanical system composed of two elastic structures in dry contact is presented. The analysis is based on the measurement of displacement ratio of the contacting elastic structures as a function of frequency due to light impulse excitation at a single point on any of the two elastic structures. The theoretical analysis depends on a very simple model of a two-degree-of-freedom system where two solid friction models are adopted in the analysis of the mathematical model. Several experiments are presented to illustrate the dominant friction mechanism of contacting surfaces within the micro slip regime in a frequency range of oscillation up to 400 Hz. It was shown experimentally that the solid friction model behaves in a way that is described as structural (hysteretic) damping. In other words, the energy dissipated due to dry friction during micro slip regime does not depend on the relative velocity between the two contacting surfaces but it is proportional to their relative displacements. The determination of the contact stiffness and damping loss factor in addition to their variation with the applied normal load was also shown.