Some important aspects of thermal elastohydrodynamic lubrication

Abstract

Thermal effect in elastohydrodynamic lubrication (EHL) has been the subject of study for the last four decades; however, some important aspects related to the physical behaviour of the lubricant in response to pressure, temperature, and shear rate remain largely neglected. This paper presents a brief review of the thermal EHL literature and sheds light on the importance of accurate characterization of the lubricant properties such as viscosity, density, rheology, and thermal conductivity. Full thermal EHL line contact simulations under steady-state and transient conditions show that using the ambient value of thermal expansivity, which has been the usual trend, may overestimate the central film thickness and introduce unrealistic features in transient EHL characteristics. Also, it is demonstrated that the most extensively used rheological equation – the sinh law – for characterizing the behaviour of shear-thinning lubricants underestimates the effect of viscous heating on EHL traction and film thickness.