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Research Papers: Elastohydrodynamic Lubrication

The Effect of Triangle-Shaped Surface Textures on the Performance of the Lubricated Point-Contacts

[+] Author and Article Information
Wen-zhong Wang

e-mail: wangwzhong@bit.edu.cn

Shanshan Li

School of Mechanical and Vehicular Engineering,
Beijing Institute of Technology,
Beijing 100081, People's Republic of China

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received May 18, 2012; final manuscript received November 4, 2012; published online March 18, 2013. Assoc. Editor: Dong Zhu.

J. Tribol 135(2), 021503 (Mar 18, 2013) (11 pages) Paper No: TRIB-12-1081; doi: 10.1115/1.4023206 History: Received May 18, 2012; Revised November 04, 2012

It has been recognized that purposefully designed surface texturing can contribute to the improvement of tribological performance of elements and friction reduction. However, its optimal parameters may depend on the operating conditions. This paper investigated the effect of a triangle-shaped dimples array on the tribological performance of the lubricated point-contacts under different lubrication regimes, based on the rotational sliding experiment of a patterned steel disk against smooth steel balls. The dimples arrays were produced by laser process and characterized by the 3D profilometer. A series of tests were conducted with different dimple parameters including depth, coverage ratio, size, and direction. Stribecklike curves were obtained to depict the transition of lubrication regimes, and the electrical contact resistance was utilized to qualitatively characterize the lubrication status. The test results showed that the dimples arrays with different sizes, depths and coverage ratios had a distinct effect on the friction behaviors. Compared with the nontextured surfaces, when the dimple depth decreased from 30μm to zero with fixed coverage ratio and size, the friction coefficient firstly decreased, and then increased. The friction coefficient finally approached that of the nontextured surface, during which the lowest value appeared at the dimple depth of approximately 10∼15μm. The coverage ratio of texture showed the similar effect on the friction coefficient. Usually, the coverage ratio of approximately 10% resulted in the lowest friction coefficient. The dimple size and direction also had obvious effects on the friction coefficient. Thus, it can be concluded that there exists a set of optimal values for the dimple depth, coverage ratio, size, and direction to realize the friction reduction.

Copyright © 2013 by ASME
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References

Figures

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Fig. 1

Tribological test rig

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Fig. 2

Schematic figure of tester and specimens

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Fig. 3

Textured disk specimens

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Fig. 4

Picture of single dimple before and after polishing along with imaginary unit cell and dimple profiles

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Fig. 5

Texture images with different coverage ratios before polishing

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Fig. 6

Texture images with different coverage ratios after polishing

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Fig. 7

Cross section profiles of dimples

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Fig. 8

surface roughness profiles

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Fig. 9

The variation of dimple area against depth obtained by re-polishing the top surface

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Fig. 10

Typical measurement results for textured surface

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Fig. 11

The variation of electrical contact resistance with sliding speed

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Fig. 12

Change of friction coefficient for textured surfaces with the different depths (side length of 443 μm and coverage ratio of 5%)

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Fig. 13

Variation of friction coefficient with speed for textured surfaces with the different depth and coverage ratio (side length of 443 μ m)

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Fig. 14

The variation of friction coefficients at different coverage ratios with a side length of 443 μm

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Fig. 15

Friction coefficients for dimple arrays with different side lengths

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Fig. 16

Friction coefficient with rotation speed with different coverage ratio and triangle direction

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Fig. 17

Surface topography after test, the arrows indicate the rotation direction of the disk. (a) CCW; (b) CW; (c) RD

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