Research Papers: Elastohydrodynamic Lubrication

Time-Temperature-Pressure Superposition in Polymer Thickened Liquid Lubricants

[+] Author and Article Information
Scott Bair

Georgia Institute of Technology,
Center for High-Pressure Rheology,
George W. Woodruff School
of Mechanical Engineering,
Atlanta, GA 30332-0405
e-mail: scott.bair@me.gatech.edu

Farrukh Qureshi

Physical & Analytical Sciences,
The Lubrizol Corporation,
29400 Lakeland Boulevard,
Wickliffe, OH 44092-2298
e-mail: Farrukh.Qureshi@Lubrizol.com

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received August 30, 2013; final manuscript received January 22, 2014; published online February 19, 2014. Assoc. Editor: Dong Zhu.

J. Tribol 136(2), 021505 (Feb 19, 2014) (6 pages) Paper No: TRIB-13-1176; doi: 10.1115/1.4026591 History: Received August 30, 2013; Revised January 22, 2014

Shear-dependent viscosities have been measured over a range of temperature and pressure for seven engine oils blended to have kinematic viscosity of 14 mm2/s at 100 °C with two base oils and four viscosity modifiers. Elevated pressure measurements were performed with a pressurized thin-film Couette viscometer and ambient pressure measurements were done with a PCS USV viscometer. These measurements were fitted to a generalized Newtonian model with the effective shear modulus specified by an empirical power-law shifting rule. The use of PAO-40 as a thickener delayed the shear-thinning to very high stress as compared with the polymers. The rate sensitivity of the oils thickened with nondispersant polymers was similar. Like the Tannas TBS viscometer, the PCS Instruments USV viscometer provides shear-dependent viscosity measurements, which can be essential for the most accurate time-temperature-pressure shifting. Viscosities measured at high viscous power in the ambient pressure viscometer, however, tend to be influenced by thermal softening and at high stress by shear cavitation.

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Fig. 1

Flow curves for the NIST standard reference material SRM2490, certified viscosities at ambient pressure and viscosities measured in the pressurized Couette viscometer at pressure of 2 MPa. Two temperatures are represented

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Fig. 2

The pressurized Couette viscometer for pressure to 700 MPa. A perfluorinated hydrocarbon occupies the lower volume to the position indicated. (Reproduced from Ref. [12] with permission from Elsevier).

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Fig. 3

Flow curves for 644

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Fig. 4

Flow curves for 645

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Fig. 5

Flow curves for 646

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Fig. 6

Flow curves for 647

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Fig. 7

Flow curves for 648

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Fig. 8

Flow curves for 649

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Fig. 9

Flow curves for 650

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Fig. 10

Measured EHL film thickness for 647 compared with the prediction of Ref. [8] using the parameters of Table 2




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