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Research Papers: Elastohydrodynamic Lubrication

Effects of Anisotropic Slip on the Elastohydrodynamic Lubrication of Circular Contacts

[+] Author and Article Information
Qie-Da Chen

Department of Materials
Science and Engineering,
National Cheng Kung University,
No. 1 University Road,
Tainan 701, Taiwan
e-mail: dreamkeith@gmail.com

Hsiang-Chin Jao

Department of Materials
Science and Engineering,
National Cheng Kung University,
No. 1 University Road,
Tainan 701, Taiwan
e-mail: q28991067@mail.ncku.edu.tw

Li-Ming Chu

Department of Mechanical Engineering,
Southern Taiwan University
of Science and Technology,
No. 1 Nantai Street,
Tainan 710, Taiwan
e-mail: lmchu@mail.stust.edu.tw

Wang-Long Li

Department of Materials
Science and Engineering,
National Cheng Kung University,
No. 1 University Road,
Tainan 701, Taiwan
e-mail: wlli@mail.ncku.edu.tw

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received June 16, 2015; final manuscript received October 15, 2015; published online February 15, 2016. Assoc. Editor: Dong Zhu.

J. Tribol 138(3), 031502 (Feb 15, 2016) (12 pages) Paper No: TRIB-15-1202; doi: 10.1115/1.4031991 History: Received June 16, 2015; Revised October 15, 2015

By coupling the equations of the modified Reynolds equation with the anisotropic slip effect, the piezoviscosity and piezodensity relations, the elasticity deformation equation, and the load equilibrium equation are solved simultaneously using the finite element method (FEM) for the elastohydrodynamic lubrication (EHL) of circular contact problems under constant load conditions. Results show that the film thickness is more sensitive to the slip length in a sliding direction (x-direction) than to the slip length in a transverse direction (y-direction). A slip in the y-direction concentrates the pressure toward the center region, and the film collects toward the central region and possesses a deeper dimple. The central pressure and coefficient of friction (COF) increase as the slip length in the y-direction increases. On the contrary, the central pressure and COF decrease as the slip length in the x-direction increases. Detailed results and animations for film thicknesses and pressure distributions are available under the “Supplemental Data” tab for this paper on the ASME Digital Collection.

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Figures

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Fig. 1

Schematic diagram for slip length

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Fig. 2

Geometry of EHL of circular contacts

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Fig. 3

Contours of pressure in the contact regions (πa2) of cases with boundary conditions: no-slip (A), slip only in x-direction (D, E, and G), and slip only in y-direction (B, C, and F)

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Fig. 4

Contours of film thicknesses in the contact regions (πa2) of cases with boundary conditions: no-slip (A), slip only in x-direction (D, E, and G), and slip only in y-direction (B, C, and F)

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Fig. 5

Pressure profiles and film shapes with different slip conditions at Y = 0

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Fig. 6

Pressure profiles and film shapes with different slip conditions at X = 0

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Fig. 7

Effects of dimensionless slip lengths on central pressures

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Fig. 8

Effects of dimensionless slip lengths on central film thicknesses

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Fig. 10

Effects of dimensionless slip lengths on minimum film thicknesses

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Fig. 9

Effects of dimensionless slip lengths on pressure spikes

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Fig. 11

Contours of von Mises stress in the X–Z plane of cases with boundary conditions: no-slip (A), slip only in x-direction (D, E, and G), and slip only in y-direction (B, C, and F) with B = 0.1

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Fig. 12

Effects of dimensionless slip lengths on maximum von Mises stress

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Fig. 13

Dimensionless velocity distribution and its components (Poiseuille and Couette flow) across the film in X-direction for no-slip case

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Fig. 14

(a) Velocity distribution across the film in the x-direction with different slip conditions (X=0.7): case C: X=0.7, H = 0.2535, and ∂P/∂X = −3.23489; case F: X = 0.7, H = 0.18872, and ∂P/∂X = −4.39612. (b) Velocity distribution across the film in the x-direction with different slip conditions (X = −1.1): case C: X = −1.1, H = 0.42461, and ∂P/∂X = 0.62354 ; case F: X = −1.1, H = 0.36846, and ∂P/∂X = 0.59227.

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Fig. 15

Effects of dimensionless slip lengths on COF

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Fig. 16

(a) Pressure profiles and film shapes with different slip conditions at Y = 0 and (b) enlargement of pressure profiles of Fig. 16(a)

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Fig. 17

(a) Pressure profiles and film shapes with different slip conditions at Y = 0 and (b) enlargement of pressure profiles of Fig. 17(a)

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