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Research Papers: Hydrodynamic Lubrication

A Theoretical Analysis of the Mixed Elastohydrodynamic Lubrication in Elliptical Contacts With an Arbitrary Entrainment Angle

[+] Author and Article Information
Wei Pu, Ying Zhang, Dong Zhu

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

Jiaxu Wang

School of Aeronautics and Astronautics,
Sichuan University,
Chengdu 610065, China
e-mail: wjx@scu.edu.cn

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received March 24, 2014; final manuscript received July 20, 2014; published online August 25, 2014. Assoc. Editor: Sinan Muftu.

J. Tribol 136(4), 041505 (Aug 25, 2014) (11 pages) Paper No: TRIB-14-1064; doi: 10.1115/1.4028126 History: Received March 24, 2014; Revised July 20, 2014

Numerical simulations of the elastohydrodynamic lubrication (EHL) have been conducted by many researchers, in which the entrainment velocity is usually parallel to one of the axes of Hertzian contact ellipse. However, in some engineering applications, such as the counterformal contacts in spiral bevel and hypoid gears, entraining velocity vector may have an oblique angle that could possibly influence the lubrication characteristics significantly. Also, a vast majority of gears operate in mixed EHL mode in which the rough surface asperity contacts and lubricant films coexist. These gears are key elements widely used for transmitting significant power in various types of vehicles and engineering machinery. Therefore, model development for the mixed EHL in elliptical contacts with an arbitrary entrainment angle is of great importance. In the present paper, a recently developed mixed EHL model is modified to consider the effect of arbitrary entraining velocity angle, and the model is validated by comparing its results with available experimental data and previous numerical analyses found in literature. Based on this, numerical simulations are conducted to systematically study the influence of entrainment angle on lubricant film thickness in wide ranges of speed, load, and contact ellipticity. The obtained results cover the entire lubrication spectrum from thick-film and thin-film lubrication all the way down to mixed and boundary lubrication. In addition, minimum film thickness prediction formula is also developed through curve-fitting of the numerical results.

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References

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Figures

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Fig. 1

Direction of lubricant entrainment

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Fig. 2

Comparison between present simulations and testing results from Ref. [28]—small θ angle cases. (a) Film thickness contours from simulations and (b) film thickness contours from measurements.

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Fig. 3

Comparison between present simulations and testing results from Ref. [28]—large θ angle cases. (a) Film thickness contours from simulations and (b) film thickness contours from measurements.

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Fig. 4

Film thickness contours from EHL solutions approaching that of a Hertzian contact as the speed decreases

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Fig. 5

Continuous transition from full-film and mixed EHL to dry contact with two honed surfaces

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Fig. 6

Contact load ratio and λ ratio as functions of speed over the entire transition

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Fig. 7

Film thickness results at different speeds: (a) ue = 50 m/s; (b) ue = 15 m/s; (c) ue = 5 m/s; (d) ue = 1 m/s; (e) ue = 0.5 m/s; and (f) ue = 0.05 m/s.

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Fig. 8

Film thickness results at different loads: (a) ue = 0.3 GPa; (b) ue = 0.5 GPa; (c) ue = 1.0 GPa; (d) ue = 1.5 GPa; (e) ue = 2.5 GPa; and (f) ue = 3.0 GPa.

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Fig. 9

Central film thickness versus entrainment angle

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Fig. 10

Minimum film thickness versus entrainment angle

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Fig. 11

Dimensionless film thickness contours from thin-film EHL solutions as the entrainment angle increases

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Fig. 12

Comparison between numerical results and those predicted by the curve-fitting formula

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