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Research Papers: Elastohydrodynamic Lubrication

Investigation of Shear-Thinning Behavior on Film Thickness and Friction Coefficient of Polyalphaolefin Base Fluids With Varying Olefin Copolymer Content

[+] Author and Article Information
Thomas J. Zolper

Department of Mechanical Engineering,
University of Wisconsin,
Platteville, WI 53818;
Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208
e-mail: Zolpert@uwplatt.edu

Yifeng He

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208;
Research Institute of Petroleum Processing,
SINOPEC,
Beijing 100083, China

Massimiliano Delferro

Chemical Sciences and Engineering Division,
Argonne National Laboratory,
Argonne, IL 60439

Paul Shiller, Gary Doll

Department of Civil Engineering,
University of Akron,
Akron, OH 44325

Babak LotfizadehDehkordi

Department of Mechanical Engineering,
University of Akron,
Akron, OH 44325

Ning Ren, Frances Lockwood

New Product Development Laboratory,
Ashland Corporation,
Lexington, KY 40509

Tobin J. Marks

Department of Chemistry,
Northwestern University,
Evanston, IL 60208

Yip-Wah Chung

Department of Mechanical Engineering;
Department of Materials Science and Engineering,
Northwestern University,
Evanston, IL 60208

Aaron Greco, Ali Erdemir

Energy Systems Division,
Argonne National Laboratory,
Argonne, IL 60439

Qian Wang

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received January 21, 2016; final manuscript received May 19, 2016; published online August 11, 2016. Assoc. Editor: Zhong Min Jin.The United States Government retains, and by accepting the article for publication, the publisher acknowledges that the United States Government retains, a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States Government purposes.

J. Tribol 139(2), 021504 (Aug 11, 2016) (9 pages) Paper No: TRIB-16-1030; doi: 10.1115/1.4033716 History: Received January 21, 2016; Revised May 19, 2016

This study investigates the rheological properties, elastohydrodynamic (EHD) film-forming capability, and friction coefficients of low molecular mass poly-α-olefin (PAO) base stocks with varying contents of high molecular mass olefin copolymers (OCPs) to assess their shear stability and their potential for energy-efficient lubrication. Several PAO–OCP mixtures were blended in order to examine the relationship between their additive content and tribological performance. Gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy were used to characterize the molecular masses and structures, respectively. Density, viscosity, EHD film thickness, and friction were measured at 303 K, 348 K, and 398 K. Film thickness and friction were studied at entrainment speeds relevant to the boundary, mixed, and full-film lubrication regimes. The PAO–OCP mixtures underwent temporary shear-thinning resulting in decreases in film thickness and hydrodynamic friction. These results demonstrate that the shear characteristics of PAO–OCP mixtures can be tuned with the OCP content and provide insight into the effects of additives on EHD characteristics.

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Figures

Grahic Jump Location
Fig. 1

Molecular structures of (a) PAO and (b) OCP

Grahic Jump Location
Fig. 2

Molecular structure of OPC-A deduced from (a) 1H NMR (400 MHz, C2D2Cl4, 403 K) and (b) 13C{1H} NMR (100 MHz, C2D2Cl4, 403 K)

Grahic Jump Location
Fig. 3

Absolute viscosity of PAO 4 (squares), PAO–OCP 10 (circles), PAO–OCP 20 (diamonds), and OCP-B (triangles) at several temperatures

Grahic Jump Location
Fig. 4

Viscosity versus pressure for (a) PAO 4, (b) PAO–OCP 10, and (c) PAO–OCP 20 at 303 K (triangles), 348 K (squares), and 398 K (diamonds)

Grahic Jump Location
Fig. 5

Measured (symbols) and calculated (lines) film thickness versus entrainment speed for (a) PAO 4, (b) PAO–OCP 10, and (c) PAO–OCP 20 at 303 K (triangles), 348 K (squares), and 398 K (diamonds) at Σ = 0.5

Grahic Jump Location
Fig. 6

Mean shear stress versus strain rate for (a) PAO 4, (b) PAO–OCP 10, and (c) PAO–OCP 20 at 303 K (triangles), 348 K (squares), and 398 K (diamonds) at Σ = 0.5

Grahic Jump Location
Fig. 7

Friction coefficient versus film thickness for (a) PAO 4, (b) PAO–OCP 10, and (c) PAO–OCP 20 at 303 K (triangles), 348 K (squares), and 398 K (diamonds) at Σ = 0.5

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