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Research Papers: Elastohydrodynamic Lubrication

Film Thickness and Rolling Resistance in Starved Elastohydrodynamic Lubrication of Point Contacts With Reflow

[+] Author and Article Information
Takashi Nogi

Japan Aerospace Exploration Agency,
7-44-1 Jindaiji-higashimachi,
Chofu, Tokyo 182-8522, Japan
e-mail: nogi.takashi@jaxa.jp

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received December 29, 2014; final manuscript received March 12, 2015; published online April 29, 2015. Assoc. Editor: Xiaolan Ai.

J. Tribol 137(4), 041502 (Oct 01, 2015) (8 pages) Paper No: TRIB-14-1317; doi: 10.1115/1.4030203 History: Received December 29, 2014; Revised March 12, 2015; Online April 29, 2015

Elastohydrodynamic lubrication (EHL) film thickness and rolling resistance play a critical role in determining friction, wear, life, and other tribological characteristics of rolling bearings. Although film thickness formulas are widely used and experimentally verified, accurate prediction of the film thickness is still difficult under starved conditions. This paper presents a numerical study of starved EHL point contacts using a nonuniform inlet film thickness obtained from a modified Coyne–Elrod boundary condition. An experimental verification of the numerical results is also presented. Based on the results of a parametric study, inlet distance formulas are obtained as a function of the initial film thickness, the fully flooded central film thickness, and the capillary number. By using the inlet distance formulas and the Hamrock–Dowson formulas, the central film thickness, the minimum film thickness, and the viscous rolling resistance can be calculated.

Copyright © 2015 by ASME
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References

Figures

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Fig. 1

Example of the boundaries and a micrograph around the contact

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Fig. 2

Example of the film thicknesses outside the boundaries

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Fig. 3

Schematic diagram of the EHL traction apparatus

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Fig. 4

Schematic diagram of the principle of the rolling resistance measurement

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Fig. 5

A set of the traction curves in the CW and CCW directions

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Fig. 6

The dimensionless pressure (top) and the dimensionless film thickness (bottom)

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Fig. 7

The ratio of the film thickness to the gap height (top) and the dimensionless shear stress (bottom)

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Fig. 8

Comparison between the numerical and experimental results for the dimensionless central film thickness

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Fig. 9

Comparison between the numerical and experimental results for the dimensionless minimum film thickness

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Fig. 10

Comparison between the numerical and experimental results for the dimensionless viscous rolling resistance

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Fig. 11

Effect of the capillary number and the dimensionless initial film thickness on the dimensionless inlet distance

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Fig. 12

Effect of the dimensionless fully flooded central film thickness on the dimensionless inlet distance

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Fig. 13

Relation between the reduction factor of the central film thickness and the inlet boundary parameter

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Fig. 14

Relation between the reduction factor of the minimum film thickness and the inlet boundary parameter

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Fig. 15

Relation between the reduction factor of the viscous rolling resistance and the inlet boundary parameter

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