Investigation of grease behavior under simple and complex displacement amplitudes conditions

Grease lubricants are extensively used in contacts, usually to reduce friction and wear. Under small amplitude sliding, as in rolling systems subject to vibration, there is significant lubricant decay. The present study analyses the fretting and reciprocating sliding response of a greased interface. Lubricant behavior is firstly investigated under small fretting amplitude to explore three domains: partial slip, scarce lubrication and full lubricated domain. Secondly, the purpose is to investigate the effect of introduction of intermittent reciprocating displacement amplitude on grease response. Friction and wear behaviors are investigated as a function of imposed small fretting displacement amplitude in both cases. The kinetics of formation and destruction of tribofilm under simple and complex displacement amplitudes is formalized through an energetic analysis.