Rheological Challenges and Opportunities for EHL

Bair, Scott; Gordon, Peter A.

doi:10.1007/1-4020-4533-6_2

Cited by 4 publications

(4 citation statements)

References 25 publications

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“…More recently, Van Leeuwen [42] has used film thickness measurements to inversely calculate the pressure viscosity coefficient, which seems to be the suitable way to determine the α-value when high pressure viscosity measurements are not available. However, Bair et al [43] contested these measurements, showing that the α-value obtained with this process could be much different values depending on the geometry (and consequent scale effect) used for the film thickness measurements.…”

Section: Appendix a Film Thickness Prediction Of Base And Bleed-oilsmentioning

confidence: 96%

On the film thickness behaviour of polymer greases at low and high speeds

Gonçalves

Graça

Campos

et al. 2015

Tribology International

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Section: Appendix a Film Thickness Prediction Of Base And Bleed-oilsmentioning

confidence: 96%

On the film thickness behaviour of polymer greases at low and high speeds

Gonçalves

Graça

Campos

et al. 2015

Tribology International

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“…The objective function is the relative difference between the experimental and numerical data. Table 4 shows the pressure-viscosity coefficients given by Gold's equation [32], α Gold This indirect prediction of the pressure-viscosity coefficient using film thickness measurements, although very useful, needs further research and these is not a clear consensus in the literature [33,34].…”

Section: Pressure-viscositymentioning

confidence: 98%

Film thickness and traction curves of wind turbine gear oils

Fernandes

Marques

Martins

et al. 2015

Tribology International

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“…With specially designed high-pressure rheometers (e.g. in Couette and capillary forms), Bair and coworkers 9,[52][53][54] showed that the generalized viscosity for shear-thinning presents a power-law form above the Newtonian limit. The measurement range of highpressure Couette viscometers is limited by thermal softening.…”

Section: Shear-thinning Rheological Fluid Modelsmentioning

confidence: 99%

Two-dimensional generalized non-Newtonian EHL lubrication: Shear rate-based solution versus shear stress-based solution

Liu

Zhang

Schneider

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part J:

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Lubricant behaves non-Newtonian at high shear stress and high shear rate. The non-Newtonian shear behavior of oil such as shear-thinning, viscoelasticity, and limiting shear stress could have influences on almost all characteristics of an elastohydrodynamic lubrication (EHL) contact, that is, the central film thickness, the coefficient of friction, and the temperature rise in the lubricating film. For example, for lubricants of large molecular weight or of polymer blended ones, there can be inlet shear-thinning, which would reduce the EHL film thickness. For the EHL traction in a rolling/sliding EHL contact, it cannot be reasonably predicted without the consideration of non-Newtonian rheology. In EHL numerical studies, the non-Newtonian properties and the constitutive equations are expressed by the concept of generalized viscosity [Formula: see text], which can be either a function of shear rate [Formula: see text] or a function of shear stress [Formula: see text]. In this way, a non-Newtonian lubrication problem could be solved as a generalized Newtonian problem based on solvers for a Newtonian EHL problem. According to the function of the generalized viscosity [Formula: see text], numerical solutions can be classified into shear rate-based ones and shear stress-based ones. In this work, these two kinds of numerical solutions are revisited. And their efficiency is compared for a two-dimensional (2D) non-Newtonian point contact EHL problem (here 2D means non-Newtonian flow in both the x and y directions). Results show that the shear rate-based numerical solution has a higher efficiency than the shear stress-based one. The shear rate-based 2D generalized Newtonian method is more suitable to analyze multiple EHL contacts in angular contact ball bearings and gears with complex 2D flow and/or transient EHL lubrication problems.

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Rheological Challenges and Opportunities for EHL

Cited by 4 publications

References 25 publications

On the film thickness behaviour of polymer greases at low and high speeds

On the film thickness behaviour of polymer greases at low and high speeds

Film thickness and traction curves of wind turbine gear oils

Two-dimensional generalized non-Newtonian EHL lubrication: Shear rate-based solution versus shear stress-based solution

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