Mass and Energy Balance of a Three-Body Tribosystem

Abstract

In the context of sustainable development and under the impulse of continuous technological progress, tribology contributes to the improvement of the life span of parts in dynamic contact and to the efficiency of mechanical systems. However, even if successes are obtained in lubrication, the tribology community struggles to build generalised laws of friction and wear in the case of dry friction. Based on the thermodynamics of open systems, we suggest an adaptation of the conservation of mass and energy equations to the tribosystem. The latter is modelled using the concepts of tribological triplet, tribological circuit and accommodation mechanisms. The tribosystem is described with four control volumes: two of them represent the first two bodies in dynamic contact; a third one is the tribofilm produced by the debris emission from the first bodies; a fourth control volume is used as an interface between the third body and the external environment. A mass balance is applied to these four control volumes by considering their interactions. An energy balance is then derived by applying the first principle of thermodynamics. Two systems of interdependent equations that describe the circulation of matter and energy flows in the tribosystem are outlined. These equations can be considered as a basis for future experimental developments that would aim at simultaneously characterising the different modes of energy dissipation in dynamic contact, qualitatively and especially quantitatively.