Effect of Entrainment Sliding Direction to the Traction Coefficient for Elastohydrodynamic Lubrication Elliptical Contacts in the Linear Isothermal Region

Abstract

In many mechanical systems, elastohydrodynamic lubrication (EHL) is apparent in the interfaces between rolling/sliding parts. Even at small slide-to-roll ratios, detailed knowledge about the oil film thickness and the traction exerted by the highly pressurized lubricant is crucial for the efficiency and reliability of such systems. In this study, we explore the impact of surface velocity direction and contact ellipticity on traction characteristics within EHL through numerical simulations using an elliptical EHL contact solver based on a fully coupled finite element approach. We present a novel master curve that correlates the traction coefficient slope with the lubricant entrainment direction and ellipticity, for elliptical EHL contacts in the piezoviscous elastic (PE) regime. We demonstrate that the master curve shows a maximum relative difference of less than 3.2% to the numerical simulation results, proving its efficacy. This curve is particularly beneficial for multibody-dynamics models, providing a reliable tool for predicting frictional forces in systems where elliptical EHL contacts, operating within the PE regime at low SRR, are prevalent.