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Research Papers: Elastohydrodynamic Lubrication

The Effects of Small Sinusoidal Load Variations in Elastohydrodynamic Line Contacts

[+] Author and Article Information
C. J. Hooke

Manufacturing and Mechanical Engineering,
University of Birmingham,
Edgbaston, Birmingham B15 2TT, UK

G. E. Morales-Espejel

Engineering and Research Centre,
SKF,
Nieuwegein 3430 DT, The Netherlands;
Université de Lyon,
INSA-Lyon CNRS,
LaMCoS UMR5259,
69621 Villeurbanne cedex, Lyon, France

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received January 28, 2015; final manuscript received September 14, 2015; published online November 11, 2015. Assoc. Editor: Daejong Kim.

J. Tribol 138(3), 031501 (Nov 11, 2015) (9 pages) Paper No: TRIB-15-1033; doi: 10.1115/1.4031854 History: Received January 28, 2015; Revised September 14, 2015

A method of determining the response of elastohydrodynamic line contacts to low amplitude, sinusoidal variations in load is presented. It is shown that the load variations alter the Hertz width, cyclically increasing and reducing the effective entrainment velocity. This produces clearance variations in the inlet, which are transported through the conjunction altering the pressure distribution as they pass. The resulting pressure and clearance changes can be many times greater than when the load changes slowly. The results are used to determine the flexibility and damping of the conjunctions. These vary depending on the number of transported waves inside the contact. It is shown that a Maxwell model rather than the usual Voigt model is required to define the contact's behavior. While the Voigt model may be used at low frequencies, it has a damping coefficient that is not unique to the contact but depends on the total system stiffness.

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References

Figures

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Fig. 1

Pressures and clearances for a 5% variation in load at a frequency f = 1.77u/b at four points in the load cycle. P = 20, S = 8, and PH = 1 GPa, rolling contact. The dashed lines show the steady values: (a) maximum load, (b) zero load, load decreasing, (c) minimum load, and (d) zero load, load increasing.

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Fig. 2

Effect of frequency on the pressures and clearances generated by the traveling wave at the contact center. The Roelands curve corresponds to the conditions of Fig. 1; the others show the effect of changing the Hertz pressure, the compressibility, and the pressure viscosity characteristics.

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Fig. 3

(a) Variation of central clearance with wavelength ratio and piezoviscous parameter, c. Incompressible, Barus fluid. Results from Ref. [3] for high c. (b) Variation of central pressure with wavelength ratio and inlet piezoviscous parameter, c. Incompressible, Barus fluid.

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Fig. 4

(a) Stiffness and damping. Maxwell model. ks is the stiffness of the surfaces. k and c are the stiffness and dampingof the contact. (b) Stiffness and damping. Voigt model. 1/K = 1/k + 1/ks, C = K2/ω2c, and Kωc.

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Fig. 5

Variation of flexibility with the number of waves across the conjunction. P = 20 and PH = 1 GPa.

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Fig. 6

Effect of starvation. P = 20, S = 8, and PH = 1 GPa. The percentage figures refer to the fraction of the fully flooded flow.

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Fig. 7

Energy loss perturbation across the contact. fb/u = 1, P = 20, S = 8, and PH = 1 GPa.

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Fig. 8

Voigt approximation, low-frequency damping coefficient

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