Quantitative elastohydrodynamic film forming for a gear oil with complex shear-thinning. (March 2016)

• Record Type: Journal Article
• Authors: Bair, Scott; Habchi, Wassim; Sperka, Petr; Hartl, Martin
• Is Part Of: Proceedings of the Institution of Mechanical Engineers. Volume 230:Number 3(2016:Mar.)
• Page Start: 289
• Page End: 299
• Publication Date: 2016-03
• Subjects: Elastohydrodynamic film thickness -- elastohydrodynamic lubrication -- rheology -- shear-thinning -- compressibility; Tribology -- Periodicals; 621.89
• DOI: 10.1177/1350650115600185
• Languages: English
• ISSNs: 1350-6501

Abstract

Perhaps the most thorough characterization of the elevated pressure properties of any commercial EHL lubricant is presented here for a gear oil. Compressibility, thermal conductivity, and low-shear viscosity were measured. Of particular interest is the shear dependence of viscosity, measured across four decades of stress, which shows two transitions each with a specific value of power-law exponent. An attempt to capture a suspected third transition at very high stress resulted in mechanical degradation of the liquid in the viscometer. Numerical simulations of a point contact between a steel ball and a glass disc showed good agreement over a range of slide-to-roll ratio for the measured central thickness. The agreement for the minimum thickness was excellent. A new result is that shear-thinning of a higher molecular weight component that occurs from 3 to 200 kPa had little effect on the film thickness and could therefore be neglected in a film thickness calculation.