Mixed Elastohydrodynamic Lubrication in a Partial Journal Bearing—Comparison Between Deterministic and Stochastic Models

[+] Author and Article Information
Mihai B. Dobrica

University of Poitiers, Solid Mechanics Laboratory, U.M.R C.N.R.S. 6610, SP2MI, Bd. Pierre et Marie Curie, BP 30179, 86962 Futuroscope Chasseneuil Cedex, Francedobrica@lms.univ-poitiers.fr

Michel Fillon, Patrick Maspeyrot

University of Poitiers, Solid Mechanics Laboratory, U.M.R C.N.R.S. 6610, SP2MI, Bd. Pierre et Marie Curie, BP 30179, 86962 Futuroscope Chasseneuil Cedex, France

J. Tribol 128(4), 778-788 (Jun 15, 2006) (11 pages) doi:10.1115/1.2345404 History: Received March 24, 2006; Revised June 15, 2006

The analysis of the mixed lubrication phenomena in journal and axial bearings represents nowadays the next step towards a better understanding of these devices, subjected to more and more severe operating conditions. While the theoretical bases required for an in-depth analysis of the mixed-lubrication regime have long been established, only small-scale numerical modeling was possible due to computing power limitations. This led to the appearance of averaging models, thus making it possible to generalize the trends observed in very small contacts, and to include them in large-scale numerical analyses. Unfortunately, a lack of experimental or numerical validations of these averaging models is observed, so that their reliability remains to be demonstrated. This paper proposes a deterministic numerical solution for the hydrodynamic component of the mixed-lubrication problem. The model is applicable to small partial journal bearings, having a few centimeters in width and diameter. Reynolds’ equation is solved on a very thin mesh, and pad deformation due to hydrodynamic pressure is taken into account. Deformation due to contact pressure is neglected, which limits the applicability of the model in those cases where extended contact is present. The results obtained with this deterministic model are compared to the stochastic solution proposed by Patir and Cheng, in both hydrodynamic and elastohydrodynamic regimes. The rough surfaces used in this study are numerically generated (Gaussian) and are either isotropic or oriented, having different correlation lengths. It is shown that the stochastic model of Patir and Cheng correctly anticipates the influence of roughness over the pressure field, for different types of roughness. However, when compared to the smooth surface solution, the correction introduced by this model only partially compensates for the differences observed with a deterministic analysis.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 9

Film thickness and pressure in the median plane (z=B∕2)

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Figure 10

Minimum average film thickness: (a) longitudinal roughness, (b) isotropic roughness, (c) transversal roughness

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Figure 11

Shaft attitude angle (γ=1∕9)

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Figure 8

Hydrodynamic pressure (DET)

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Figure 5

Isotropic surface (γ=1, βx=βy=120μm)

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Figure 3

Isotropic surface (γ=1, βx=βy=270μm)

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Figure 1

Partial journal bearing geometry

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Figure 17

Minimum average film thickness at z=B∕2

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Figure 18

Friction torque (γ=1∕9)

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Figure 12

Friction torque (γ=1∕9)

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Figure 13

Friction torque (γ=1)

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Figure 7

Film thickness (DET)

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Figure 14

Friction torque (γ=9)

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Figure 4

Non-isotropic surface (γ=9, βx=810μm, βy=90μm)

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Figure 15

Pad displacement (DET)

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Figure 2

Film thickness in Cartesian reference system

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Figure 16

Film thickness and pressure in the median plane (z=B∕2)



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