Study On Transition Layer Model And Its Lubrication Properties

The influence on lubricant exerted by the surface of friction pair can be ignored in conventional lubrication; however, such influence becomes obvious when the size of the gap between surfaces of friction pair reduces to micro/nano scale. In this paper, a transition layer model is presented to depict the variation of the viscosity of the lubricant in micro/nano scale clearance. The viscosity variation in transition layer model is divided into three layers, namely two transition layers close to surfaces of friction pair and one middle fluid layer far away from surfaces of friction pair. The lubricant in transition layer is influenced by solid walls. The closer it is to the solid walls, the greater the influence is. Thus, the viscosity of the lubricant can be obtained according to the distance away from solid walls. The viscosity of the lubricant in fluid layer keeps constant because it is far away from the solid walls and can be considered not affected by them.Mathematic model of effective viscosity of the lubricant in transition layer is built and 2D and 3D Reynolds equations are deduced based on such model. The Reynolds equations are afterwards solved and lubrication properties of transiton layer are discussed and analyzed according to the computing results.The results reveal that the transition layer can be ignored when its proportion to the whole gap is very small and the lubricant properties are similar with that of conventional fluids. However, when the proportion is large enough, its lubricant features differ from conventional fluids distinctively. This model can explain the characteristics such as size-effects in micro-scale gap and has a rosy application prospect.