An approach for determination of lubricant properties at elliptical elastohydrodynamic contacts using a twin-disc test device and a numerical traction model

Abstract

High-pressure lubricant properties are important when friction coefficients and power losses are evaluated in elastohydrodynamic (EHL) contacts. An approach was developed to determine the limiting shear stress and actual viscosity properties of lubricants using a numerical traction model based on elliptical EHL contact and traction curves, measured at a wide range of temperatures and pressures with a twin-disc test device. The tests were carried out in pure fluid film at high Hertzian pressures with finely polished surfaces. Each lubricant was tested at 135 test points, where traction coefficients and bulk temperatures were measured. The lubricant parameters in the traction model were adjusted so that the calculated results matched the experimental measurements at all test points. In general, there is a good correlation between the calculated results and the experimental measurements. The influence of pressure on limiting shear stress and actual viscosity is less significant for polyalphaolefin (PAO) oil than for mineral oil.