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A critical evaluation of film thickness‐derived pressure–viscosity coefficients
Author(s) -
Bair Scott
Publication year - 2015
Publication title -
lubrication science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.632
H-Index - 36
eISSN - 1557-6833
pISSN - 0954-0075
DOI - 10.1002/ls.1284
Subject(s) - viscometer , viscosity , thermodynamics , ubbelohde viscometer , reduced viscosity , temperature dependence of liquid viscosity , newtonian fluid , materials science , relative viscosity , inherent viscosity , pressure coefficient , chemistry , mechanics , intrinsic viscosity , composite material , physics , polymer
A single parameter, the pressure–viscosity coefficient, α , quantifies the pressure dependence of the viscosity of the liquid in elastohydrodynamic lubrication (EHL). Most published values of α have not been obtained from measurements of viscosity as a function of pressure. Rather, these effective pressure–viscosity coefficients have been derived from the measurement of the EHL film thickness, a more difficult procedure. In this article, five well‐characterized liquids that should be Newtonian in the EHL inlet are identified for which film‐derived coefficients have been reported. These coefficients are compared with coefficients derived from published viscosity correlations and new viscosity measurements. The film‐derived coefficients are found to not be an accurate representation of the piezoviscous response. The procedure of deriving a pressure–viscosity coefficient from a film thickness measurement does not offer an alternative to the simpler and easier viscometer measurement. Copyright © 2014 John Wiley & Sons, Ltd.