A Generalized Non-Newtonian Fluid Model Incorporated Into Elastohydrodynamic Lubrication

Abstract

A generalized Reynolds equation for the non-Newtonian fluid, which can incorporate most of the published rheological models, is proposed. The solution of the isothermal EHL line contact lubricated by a non-Newtonian fluid is obtained by applying the Newton-Raphson method. The results of an isothermal non-Newtonian EHL line contact model with different rheological laws and the results of a thermal Newtonian EHL model are presented. Under low load and high rolling velocity conditions, the thermal effects caused by slip have a greater influence on the film shape and pressure distribution than the non-Newtonian effects. For low slip and under heavy load conditions the non-Newtonian behavior of fluid significantly influences the traction coefficient, while thermal effects have a great influence on the traction in case of high slip. The comparison between numerical and experimental results shows that the nonlinear viscous Eyring model overestimates the traction coefficient when high viscosity oil is subjected to a heavy load and low slip conditions. In this case, only the visco-plastic models can predict the traction value. The visco-elastic behavior of the fluid is important at very low slip conditions and it can slightly reduce the traction value.