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Free-Surface Grease Flow: Influence of Surface Roughness and Temperature

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Abstract

Grease flow in grease-lubricated systems can often be qualified as free-surface flow. It occurs, for example, in rolling bearings after the churning phase or on open gears. Here only a fraction of the bearing or gearbox volume is filled with grease. Part of the grease is flowing in relatively thin layers induced by centrifugal forces caused by rotation of the various components. In this paper, a model problem is investigated in the form of a free-surface flow of grease on a rotating disc. Experiments have been performed where the onset of flow and remaining grease have been studied varying the surface roughness, temperature and the centrifugal forces. The experiments have been coupled to analytical models describing the flow and temperature distribution in the grease. It was found that the impact of surface roughness could be neglected. The flow is determined by the centrifugal forces and rheology of the grease. Temperature effects the rheology but also the oil separation creating low shear strength/low viscosity layers at the surface.

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Notes

  1. The definition of the material derivative is also included in Westerberg et al. [13]. There is, however, an error in the definition in that paper; the definition presented here is the correct one.

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Acknowledgments

This work is funded by the Swedish Research Council (VR).

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Authors and Affiliations

  1. Division of Fluid and Experimental Mechanics, Luleå University of Technology, 971 87, Luleå, Sweden

    Lars G. Westerberg

  2. Division of Machine Elements, Luleå University of Technology, 971 87, Luleå, Sweden

    Erik Höglund & Jinxia Li

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

    Piet M. Lugt & Pieter Baart

Authors
  1. Lars G. Westerberg
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  2. Erik Höglund
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  3. Piet M. Lugt
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  4. Jinxia Li
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  5. Pieter Baart
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Corresponding author

Correspondence to Lars G. Westerberg.

Additional information

This article is part of the Topical Collection on STLE Tribology Frontiers Conference 2014.

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Westerberg, L.G., Höglund, E., Lugt, P.M. et al. Free-Surface Grease Flow: Influence of Surface Roughness and Temperature. Tribol Lett 59, 18 (2015). https://doi.org/10.1007/s11249-015-0537-y

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  • DOI: https://doi.org/10.1007/s11249-015-0537-y

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