Thermal elastohydrodynamic lubrication of rolling/sliding line contacts using a mixture of Newtonian and power law fluids

Abstract

Thermal elastohydrodynamic lubrication (EHL) behaviour of rolling/sliding line contacts is investigated numerically using a mixed rheological fluid model. The lubricant used is a homogeneous mixture of Newtonian base oil and power law fluid with varying volume fraction, viscosity ratio (VR), and power law index. The velocity distribution across the fluid film for the mixed rheological fluid model is obtained using perturbation method to derive Reynolds and mean temperature equations. The TEHL characteristics computed for the mixture are found to depend upon the effective viscosity of the lubricant which, besides thermal effect, is governed by the superposition of shear thinning and piezo-thickening effects of the non-Newtonian fluid additive. Thermal effect is found to be a function of additive volume fraction, VR, and power law index. The mixtures yield thicker fluid films along with an increase in coefficient of friction in most of the cases. Therefore, a judicious selection of additive fluid with an appropriate volume fraction is recommended in order to achieve fairly thick fluid films at tolerable levels of friction.