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Research Papers: Elastohydrodynamic Lubrication

Numerical Solution of Mixed Thermal Elastohydrodynamic Lubrication in Point Contacts With Three-Dimensional Surface Roughness

[+] Author and Article Information
Xiaopeng Wang

School of Aeronautics and Astronautics,
Sichuan University,
Chengdu 610065, China

Yuchuan Liu

Mechanical Engineering Department,
Northwestern University,
Evanston, IL 60208

Dong Zhu

School of Aeronautics and Astronautics,
Sichuan University,
Chengdu 610065, China
e-mail: DongZhu@Mail.com

1Present address: GM Powertrain, Pontiac, MI.

2Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received July 6, 2015; final manuscript received January 18, 2016; published online June 15, 2016. Assoc. Editor: Xiaolan Ai.

J. Tribol 139(1), 011501 (Jun 15, 2016) (12 pages) Paper No: TRIB-15-1245; doi: 10.1115/1.4032963 History: Received July 06, 2015; Revised January 18, 2016

Elastohydrodynamic lubrication (EHL) is a common mode of fluid-film lubrication in which many machine elements operate. Its thermal behavior is an important concern especially for components working under extreme conditions such as high speeds, heavy loads, and surfaces with significant roughness. Previous thermal EHL (TEHL) studies focused only on the cases with smooth surfaces under the full-film lubrication condition. The present study intends to develop a more realistic unified TEHL model for point contact problems that is capable of simulating the entire transition of lubrication status from the full-film and mixed lubrication all the way down to boundary lubrication with real machined roughness. The model consists of the generalized Reynolds equation, elasticity equation, film thickness equation, and those for lubricant rheology in combination with the energy equation for the lubricant film and the surface temperature equations. The solution algorithms based on the improved semi-system approach have demonstrated a good ability to achieve stable solutions with fast convergence under severe operating conditions. Lubricant film thickness variation and temperature rises in the lubricant film and on the surfaces during the entire transition have been investigated. It appears that this model can be used to predict mixed TEHL characteristics in a wide range of operating conditions with or without three-dimensional (3D) surface roughness involved. Therefore, it can be employed as a useful tool in engineering analyses.

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References

Figures

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Fig. 1

Sketch of solution domains

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Fig. 2

Overall solution procedure

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Fig. 3

Midfilm temperature distribution

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Fig. 4

Film thickness, pressure and midfilm temperature rise variations along the X-axis

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Fig. 5

Temperature rise distribution in the film on the X–Z cross section: W = 450 N, ph = 1.380 GPa, U = 0.8 m/s, and S = 0.3

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Fig. 6

Temperature rise distributions on the midfilm layer as well as on the two surfaces: W = 450 N, ph = 1.380 GPa, U = 0.8 m/s, and S = 0.3

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Fig. 7

Temperature rise on the X–Z plane affected by film thickness: W = 56.3 N, ph = 0.690 GPa, and S = 0. (a) U = 0.01 m/s; (b) U = 0.1 m/s; and (c) U = 1.0 m/s.

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Fig. 8

Effect of slide-to-roll ratio on TEHL characteristics: (a) pressure; (b) film thickness; and (c) midfilm temperature rise

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Fig. 9

Effects of rolling speed and slide-to-roll ratio on maximum temperature rise in the film

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Fig. 10

Effect of applied load on the TEHL performance

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Fig. 11

A sample case for the TEHL with sinusoidal roughness: W*= 0.5119 × 10−5, U*= 0.1820 × 10−11, G*= 3495, S = 0.2, and ph = 1.38 GPa. (a) Rough surface topography; (b) film thickness, pressure and midfilm temperature rise variations along the X-axis; (c) pressure contour; (d) film thickness contour; and (e) midfilm temperature contour.

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Fig. 12

A sample case for the TEHL with real machined roughness: W*= 0.5119 × 10−5, U*= 0.910 × 10−11, G*= 3495, S = 0.2, and ph = 1.38 GPa. (a) Rough surface topography; (b) film thickness, pressure and midfilm temperature rise variations along the X-axis; (c) pressure contour; (d) film thickness contour; and (e) midfilm temperature contour.

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Fig. 13

Comparison between TEHL cases with and without roughness: W*= 0.5119 × 10−5, U*= 0.910 × 10−11, G*= 3495, S = 0.2, and ph = 1.38 GPa

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Fig. 14

Transition from boundary and mixed to full-film lubrication: U*= 0.910 × 10−150.910 × 10−9, W*= 0.5119 × 10−5, G*= 3495, S = 0.2, and ph = 1.38 GPa

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Fig. 15

Summary for the transition over a wide range of entraining speed: U*= 0.910 × 10−150.910 × 10−9, W*= 0.5119 × 10−5, G*= 3495, S = 0.2, and ph = 1.38 GPa

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