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Research Papers: Elastohydrodynamic Lubrication

Film Thickness Modulations in Starved Elastohydrodynamically Lubricated Contacts Induced by Time-Varying Lubricant Supply

[+] Author and Article Information
C. H. Venner

Faculty of Engineering Technology, Department of Engineering Fluid Dynamics, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands

G. Popovici, P. M. Lugt

 SKF Engineering and Research Centre, P.O. Box 2350, 3430 DT Nieuwegein, The Netherlands

M. Organisciak

LAMCOS, INSA de Lyon, 20 Avenue Albert Einstein, 69621 Villeurbanne Cedex, France

J. Tribol 130(4), 041501 (Aug 01, 2008) (10 pages) doi:10.1115/1.2958069 History: Received December 08, 2006; Revised May 29, 2008; Published August 01, 2008

Many elastohydrodynamically lubricated contacts in practical applications, e.g., in bearings, operate in the starved lubrication regime. As a result their performance is sensitive to variations of the lubricant layers present on the surfaces, which form the supply to the contact. Their shape is often determined by previous overrollings of the track and also by replenishment mechanisms and various migration effects. Variations of the layers induced in the direction of rolling lead to a time-varying lubricant supply to the contact. In this paper, by means of numerical simulations using a starved lubrication model, the film thickness modulations in the center of the contact induced by a harmonically varying inlet supply have been investigated. First, for a given load condition and layer wavelength, the effect of the nominal layer thickness (degree of starvation) and the layer variation amplitude is illustrated. Subsequently, using results for different load conditions, wavelengths, and degrees of starvation, it is shown that the response of the contact to such variations is determined by a nondimensional parameter, which represents the ratio of the entrainment length of the contact to the wavelength of the induced variation, and by the degree of starvation. A simple formula is presented for use in engineering predicting the ratio of the amplitude of the film modulations in the center of the contact to the amplitude of the layer variations in the inlet.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic representation of an EHL contact operating in the starved regime: Centerline film profile and lubricant supply layers (left) and map of starved and pressurized regions (right). Direction of rolling is indicated by the arrows.

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Figure 2

Schematic representation of the centerline of a starved EHL contact for two cases in which the lubricant supply varies as a function of time: nonuniform layer thickness on smooth surface (left) and smooth (fluid) surface layer on a nonsmooth surface of one of the contacting elements

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Figure 3

P(X,Y) (top), H(X,Y) (center), and θ(X,Y) (bottom); steady state solution, M=100, L=10, Hoil=0.5Hcff

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Figure 4

Contour plot of θH(X,Y); steady state solution, M=100, L=10, and Hoil=0.5Hcff

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Figure 5

Snapshot at a given time of P(X,Y) (top), H(X,Y) (center), and θ(X,Y) (bottom); transient solution, M=100, L=10, Hoil=0.5Hcff, foil=0.2, and W=0.5

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Figure 6

Contour plot θH(X,Y); snapshot of transient solution, M=100, L=10, and H¯oil=0.5Hcff

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Figure 7

Snapshot of centerline profiles P(X,0), H(X,0), and θH(X,0) for a fixed degree of starvation H¯oil=0.5Hcff and varying relative layer amplitude foil=0.1, 0.2, 0.5, 0.7, and 1.0

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Figure 8

Snapshot of centerline profiles H(X,0) and θH(X,0) for a fixed relative layer amplitude foil=0.2 and varying degrees of starvation: H¯oil∕Hcff=2,1,0.5,0.2

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Figure 9

Corrected relative amplitude of film thickness modulations ρ¯(ph)Ac∕Ai for different loading conditions, wavelengths, and degrees of starvation as a function of ∇s

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Figure 10

Stylistic representation of the behavior shown in Fig. 9.

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Figure 11

Corrected relative amplitude of film thickness modulations ρ¯(ph)Ac∕Ai induced by lubricant supply oscillations for different degrees of starvation as a function of the dimensionless parameter ∇̃s. The drawn line indicates the predictions of Eq. 17.

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