Cavitation within the framework of reduced description of mixed lubrication

Abstract

The principles of simulation of lubricated contacts under conditions of mixed lubrication based on a simultaneous solution of Reynolds equation and equations of elasticity are very well established. One of the main assumptions of such calculations is continuity of the lubricant. Simple estimations, however, show that in a typical lubricated contact large negative pressures (tensile stresses) should appear. This means that the lubricating fluid gets thermodynamically instable and can cavitate. The cavitation influences both the friction behaviour and especially wear in lubricated contacts. A complete description of mixed lubrication should therefore take into account the cavitation process. Even under assumptions of continuity, elastohydrodynamic problems still require much efforts and calculation time, in particular for simulation of large systems on account of fractal surface topography. In the present paper we propose a reduced description of cavitation process based on numerical solutions of Reynolds equations and equations for bubble growth. We show that a lubricated contact with cavitation can be described within the framework of our reduced description with good precision by using a kinetic equation for the fluid force.