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Is Elastohydrodynamic Minimum Film Thickness Truly Governed by Inlet Rheology?

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Abstract

This work investigates the governing mechanisms of minimum film thickness in elastohydrodynamic lubricated contacts. Up until now, it was thought to be governed by lubricant rheology in the low-pressure contact inlet. Through numerical simulations of EHL line and circular contacts, lubricated with fluids having the same low-pressure viscosity, but a very different response at high-pressure, minimum film thickness is shown to be governed by lubricant inlet rheology only in the theoretical line contact configuration. In real contacts however, it is not only governed by inlet rheology, but also by the high-pressure viscosity response of the lubricant. It is observed that the greater the viscosity at high pressure, the lower the minimum film thickness would be, as a result of reduced lateral flow out of the contact. Conservation of mass requires then that a higher minimum film thickness would be attained along the central line of the contact, in the entrainment direction. These findings corroborate well with experimental observations.

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Data availability

The authors declare that all data supporting the findings of this study are available within the article.

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Acknowledgements

Film thickness measurements were carried out with the support of the Czech Science Foundation Project No. 21-28352S.

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Authors and Affiliations

  1. Department of Industrial and Mechanical Engineering, Lebanese American University, Byblos, Lebanon

    W. Habchi

  2. Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2896/2, 61669, Brno, Czech Republic

    P. Sperka

  3. Georgia Institute of Technology, Center for High-Pressure Rheology, George W. Woodruff School of Mechanical Engineering, Atlanta, GA, 30332-0405, USA

    S. Bair

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  1. W. Habchi
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  2. P. Sperka
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  3. S. Bair
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Contributions

WH wrote the main manuscript and carried out the numerical simulations. PS carried out the experiments. SB worked out the rheological modeling. All authors reviewed the manuscript.

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Correspondence to W. Habchi.

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Habchi, W., Sperka, P. & Bair, S. Is Elastohydrodynamic Minimum Film Thickness Truly Governed by Inlet Rheology?. Tribol Lett 71, 96 (2023). https://doi.org/10.1007/s11249-023-01771-y

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