Modeling the consequences of local kinematics of the first body on friction and on third body sources in wear

Wear can be considered as a third body flow that is definitely ejected from the contact. This implies a source flow (particle detachment from first bodies) and an internal flow (displacement of these particles in the contact surface). The formation and fragmentation involved in surface tribological transformation (STT) is the main origin of this source flow. Therefore, modeling wear, i.e. writing the equation of flow equilibrium, requires understanding the STT formation. In order to explain the source flow, the first step is to determine the phenomena responsible for particle detachment. To help this determination, a finite element simulation has been undertaken to model the friction contact between two perfectly smooth first bodies. These simulations have enabled the local contact conditions (kinematics, tribological state, contact stresses, etc.) to be obtained. The kinematics shows the existence of local impacts and local slidings at high frequencies moving through the contact surface. These local phenomena are responsible for much higher local normal and tangential stresses than those expected for a smooth surface. The repeated local impact (high normal stress) and local sliding (high tangential stress) on the contact interface can explain the particle detachment from the contact surface. An investigation on the influence of different parameters has shown the relative role of friction, speed and applied load on local contact conditions.