The rheological assumptions of classical EHL: What went wrong?

The field of elastohydrodynamic lubrication (EHL) now has two very different approaches to the problem. For the first approach, two assumptions regarding the pressure, temperature and shear dependence of viscosity have been essential to the way that classical EHL developed over the last forty years....

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Bibliographic Details
Published in:Tribology international 2019-03, Vol.131, p.45-50
Main Author: Bair, Scott
Format: Article
Language:English
Subjects:
Classical EHL
Elastohydrodynamic lubrication
Lubrication
Pathological science
Pressure dependence
Quantitative EHL
Rheological properties
Rheology
Shear rate
Shear stress
Temperature dependence
Viscosity
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Summary:The field of elastohydrodynamic lubrication (EHL) now has two very different approaches to the problem. For the first approach, two assumptions regarding the pressure, temperature and shear dependence of viscosity have been essential to the way that classical EHL developed over the last forty years. 1. The liquid in the inlet zone responds in Newtonian fashion. 2. The shear stress versus shear rate relationship of the liquid has the same form as the average shear stress versus average shear rate obtained from a traction curve. The new, quantitative, approach employs viscosities measured in instruments which do not rely upon these assumptions. There has been a rapid succession of advances in understanding of film forming and friction under the new approach. •Two assumptions regarding rheology have been essential to classical EHL.•Classical EHL has avoided using viscosity obtained from viscometers.•Primary measurements of viscosity would have allowed testing of these assumptions.•Real pressure-viscosity response does not support the assumptions.
ISSN:0301-679X
1879-2464
DOI:10.1016/j.triboint.2018.10.020