Interactions Among Friction, Wear, and System Stiffness—Part 2: Vibrations Induced by Dry Friction

Different types of vibrations induced by dry friction are investigated by means of a model apparatus described in Part 1. The structural model is obtained from the measurement of the modal frequencies and damping ratios of three degrees of freedom. The oscillations in the normal and frictional forces, as well as the slider vibrations, have been measured and analyzed. As the normal load is increased, four different regions of vibrations are observed corresponding to the four friction regimes discussed in a companion paper. Small oscillations are encountered at low values of the normal load and they are possibly caused by random surface irregularities. The vibration characteristics are changed when transition occurs from steady state friction. When the normal load is further increased, self-excited periodic vibrations are produced. The spectra of the oscillations are related to the modal frequencies. Self-excited vibrations are analyzed on the basis of the experimental data.