0
RESEARCH PAPERS

An Application of a Free Volume Model to Lubricant Rheology I—Dependence of Viscosity on Temperature and Pressure

[+] Author and Article Information
S. Yasutomi, S. Bair, W. O. Winer

School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Ga. 30332

J. Tribol 106(2), 291-302 (Apr 01, 1984) (12 pages) doi:10.1115/1.3260907 History: Received April 18, 1983; Online October 29, 2009

Abstract

Analyses of the dependence of lubricant viscosity on temperature and pressure, μ(T,P), have been carried out by using a modified WLF equation in which pressure effects on viscosity are given in terms of the pressure dependence of the glass transition temperature, Tg , and of thermal expansivity of free volume, αf .

log μ(T,P)=
  log μg−C1•(T−Tg(P))•F(P)C2+(T−Tg(P))•F(P)
where C1 and C2 are well known WLF constants, and μg is a viscosity at Tg . Tg (P) and F(P) are functions for describing the pressure dependence of Tg and αf , respectively. On the basis of the iso-viscous concept for Tg (P), μg has been assumed to have a constant value, 1 TPa•s, at any pressure (SCHEME I). SCHEME I yields a reasonable variation in Tg and αf with pressure for synthetic lubricants, while this analysis suggests a lower μg for mineral oils. In order to improve the applicability of the free volume model, a reference temperature Ts (P), at which the viscosity is 10 MPa•s, has been introduced instead of Tg (P) (SCHEME II). Analyses of dielectric transition for some lubricants and of μ(T,P) in the ASME Pressure-Viscosity Report have confirmed the excellent applicability of the present free volume model over wide ranges of temperature and pressure.

Copyright © 1984 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In