The Shear-Thinning Elastohydrodynamic Film Thickness of a Two-Component Mixture

journal article - other

English

Lubricant base oils are often blends of different molecular weight cuts to arrive at a specified ambient pressure viscosity and, to improve the temperature-viscosity behavior or to simply increase the viscosity, viscosity-modifying polymer additives are often added to the base oil. This paper investigates the effect of mixture rheology on EHL film thickness using EHL contact measurements and a full numerical analysis for three synthetic lubricants including two single-component lubricants PAO650, and PAO100 and a mixture of these. The pressure and shear dependences of the viscosity of these lubricants were measured with high-pressure viscometers; viscosities were not adjusted to fit experiment. The point contact film thicknesses for these lubricants in pure rolling were measured using a thin-film colorimetric interferometry apparatus. Numerical simulations based on the measured rheology show very good agreement with the measurements of film thickness while the Newtonian prediction is up to twice the measurement. These results validate the use of realistic shear-thinning and pressure-viscosity models which originate from viscosity measurements. It is conceivable that simulation may provide a means to "engineer" lubricants with the optimum balance of film-thickness and friction though intelligent mixing of components.

EHL; elastohydrodynamics; rheology; film thickness; shear-thinning; non-Newtonian; viscosity

LIU, Y.; WANG, G.J.; KŘUPKA, I.; HARTL, M.; BAIR, S.

2008

17. 4. 2008

ASME

USA

0742-4787

ASME Transaction, Journal of Tribology

130

2

United States of America

021502-1

021502-7

7