Tribological investigation of a greased contact subjected to contact dynamic instability

A systematic approach to the stick-slip problem of a greased contact is proposed, combining experimental tribological analyses with numerical dynamic simulations. Considering the specific application case of a mechanical spring-brake, the lubricated contact is here analysed. The stick-slip instability on such contact is the result of the coupling between the brake dynamics and the frictional response of the greased contact. The local frictional response has been characterized by experimental tests carried out on a tribometer, reproducing as close as possible the operating parameters. The contact conditions bringing to stick-slip instability are then investigated. The local frictional response is coupled with the system dynamics by using lumped numerical model, in order to better evaluate the unstable dynamic response of the system.