Kvantitativní popis formování elastohydrodynamického mazacího filmu u převodových olejů s komplexní smykovým řídnutím

Quantitative elastohydrodynamic film forming for a gear oil with complex shear-thinning

journal article in Web of Science

en

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.

V článku je prezentována detailní analýza vlastností maziva za zvýšených tlaků používaného v komerčních aplikacích pro elastohydrodynamické mázání ozubení. Změřené reologické vlastnosti byly použity v termálním MKP numerickém řešení a výsledky simulací porovnány s měřením na optickém tribometru využívající optickou interferenci. Byla pozorována velmi dobrá shoda u minimální tloušťky. Výsledky poukazují na malý vliv smykového řídnutí vysokomolekulárních látek, které nastává mezi 3 a 200 kPa, na tloušťku mazací vrstvy.

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.

tloušťka filmu, elastohydrodynamický režim mazání, reologie, smykové řídnutí, stlačitelnost

elastohydrodynamic film thickness, elastohydrodynamic lubrication, rheology, shear-thinning, compressibility

31.03.2016

SAGE Publications

1350-6501

230

3

289–299

11