Identification of dynamic contact instabilities generated by braking materials

The occurrence of unstable friction-induced vibrations is a major issue for braking manufacturers, as they lead to annoying noise, structure vibrations and brake surface degradation. Understanding the underlying causes of frictional instabilities, arising during the sliding between two bodies, is necessary for developing solutions and countermeasures. For this purpose, in this work, an experimental and numerical investigation of contact instabilities has been performed. Mode coupling and negative friction-velocity slope instabilities have been numerically investigated by both lumped-parameter and finite element models. As well, an experimental campaign has been carried out for recovering the frictional and vibrational response of braking materials under different boundary conditions. The comparison between numerical and experimental results allows validating a new methodology, based on the study of the phase shift between the tangential and normal vibrational responses, in order to distinguish the different types of contact instabilities.