Effects of adsorption layers and elastic deformation on thin-film lubrication of circular contacts with non-Newtonian lubricants

Abstract

Purpose The modified Reynolds equation for non-Newtonian lubricant is derived using the viscous adsorption theory for thin-film elastohydrodynamic lubrication (TFEHL) of circular contacts. The proposed model can reasonably calculate the phenomenon in the thin-film lubrication (TFL) unexplained by the conventional EHL model. The differences between classical EHL and TFEHL with the non-Newtonian lubricants are discussed. Design/methodology/approach The power-law lubricating film between the elastic surfaces is modeled in the form of three layers: two adsorption layers on each surface and one middle layer. The modified Reynolds equation with power-law fluid is derived for TFEHL of circular contacts using the viscous adsorption theory. The finite difference method and the Gauss–Seidel iteration method are used to solve the modified Reynolds equation, elasticity deformation, lubricant rheology equations and load balance equations simultaneously. Findings The simulation results reveal that the present model can reasonably calculate the pressure distribution, the film thickness, the velocity distribution and the average viscosity in TFL with non-Newtonian lubricants. The thickness and viscosity of the adsorption layer and the flow index significantly influence the lubrication characteristics of the contact conjunction. Originality/value The present model can reasonably predict the average viscosity, the turning point and the derivation (log film thickness vs log speed) phenomena in the TFEHL under constant load conditions.

A review of recent advances in tribology

“…The numerical studies on wall slip found potential applications that a proper arrangement of slipping domains or a combination of slipping patch and surface texture would bring about even better load carrying capacity for bearings [605,607]. Another layered model has been developed for assessing the effect of adsorption films on lubrication, and numerical results predict a film thicknessvelocity (h-v) dependence in a better agreement with that measured in thin film EHL [608]. In numerical solutions of thin film lubrication when film thickness decreases down to a few nanometers, surface forces due to the van de Waals interactions and electrostatic double layer have to be incorporated [589], and they are found to contribute significantly to the film formation that prevents surfaces from sticking at zero speed.…”