Synergy of Viscosity Wedge and Squeeze Under Zero Entrainment Velocity in EHL Contacts
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ORIGINAL PAPER
Synergy of Viscosity Wedge and Squeeze Under Zero Entrainment Velocity in EHL Contacts Bilel Meziane1 · Nicolas Fillot1 · Guillermo E. Morales‑Espejel1,2 Received: 18 March 2020 / Accepted: 10 June 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In an elastohydrodynamic lubricated (EHL) contact under Zero Entrainment Velocity (ZEV) condition, surfaces cannot be separated by hydrodynamic lift. In this work, two other phenomena responsible for a film thickness build-up in ZEV contacts are studied using a numerical model. First, the thermal effect called “viscosity wedge” is investigated in steady-state conditions. Second, the “squeeze” effect is described in an environment where dynamic (time dependent) loads are considered. Then, both the viscosity wedge and squeeze effects are considered together. For each one of the two mechanisms, a characteristic time is considered. The ratio of these two times allows the identification of a dominant effect. Depending on this ratio, a prediction is attempted using semi-analytical models describing each effect. For an ideal set of parameters, it is shown that the combination of squeeze and viscosity wedge in EHL contact under ZEV allows for an enhanced performance. Keywords Elastohydrodynamic · Zero entrainment velocity · Viscosity wedge · Squeeze List of Symbols Superscripts A Steady-state thermal conditions B Transient isothermal conditions C Transient thermal conditions * Semi-analytical formula Subscripts 1,2 Solids 1 and 2, respectively c Central—film thickness f Fluid m Minimum—film thickness min Minimum—overtime Variables (Unit) a (m) Dry contact radius(Hertz) av (K−1) Parameter for the Murnaghan density formula aCY (−) Parameter for the Carreau–Yasuda nonNewtonian viscosity formula * Nicolas Fillot nicolas.fillot@insa‑lyon.fr 1
Univ Lyon, INSA-Lyon, CNRS UMR5259, LaMCoS, 69621 Lyon, France
SKF Research and Technology Development, 3992 AE Houten, The Netherlands
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A1 (K) Coefficient for the WLF viscosity correlation A2 (Pa−1) Coefficient for the WLF viscosity correlation B1 (Pa−1) Coefficient for the WLF viscosity correlation B2 (−) Coefficient for the WLF viscosity correlation C1 (−) Coefficient for the WLF viscosity correlation C2 (−) Coefficient for the WLF viscosity correlation Cp (J k g−1 K−1) Heat capacity E (Pa) Young modulus ′ E (Pa) Material parameter F (−) Variable for the WLF viscosity correlation GCY (Pa) Parameter for the Carreau–Yasuda nonNewtonian viscosity formula h (m) Film thickness h0 (m) Rigid body separation Wang∗ hc (m) Transient semi-analytical formula for the prediction of hc hA∗ (m) Steady-state semi-analytical formula for m the prediction of hm k (W m−1 K−1) Thermal conductivity
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K00 (−) Parameter for the Murnaghan density formula KM (−) Parameter for the Murnaghan density formula ′ KM (−) Parameter for the Murnaghan density formula L (−) Dimensionless Moes parameter M (−) Dimensionless Moes parameter n
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