Showing papers by "Scott Bair published in 2005"
TL;DR: In this article, a conclusive demonstration has been provided that the nature of shear-thinning, that affects both film thickness and traction in EHL contacts, follows the ordinary power-law rule that has been described by many empirical models of which Carreau is but one example.
Abstract: A conclusive demonstration has been provided that the nature of the shear-thinning, that affects both film thickness and traction in EHL contacts, follows the ordinary power-law rule that has been described by many empirical models of which Carreau is but one example. This was accomplished by accurate measurements in viscometers of the shear response of a PAO that possesses a very low critical stress for shear-thinning and accurate measurements in-contact of film thickness and traction under conditions which accentuate the shear-thinning effect. The in-contact central film thickness and traction were entirely predictable from the rheological properties obtained from viscometers using simple calculations. These data should be invaluable to researchers endeavoring to accurately simulate Hertz zone behavior since the shear-thinning rheology is extensively characterized and accurate in-contact data are available to test. In addition, a new model has been introduced that may be useful for the rheological characterization of mixtures.
66 citations
01 Jan 2005
TL;DR: In this paper, a sliding effect correction for rolling elastohydrodynamic (EHD) contacts has been proposed, which can be applied to any classical Newtonian prediction of film thickness for single component liquids having ordinary power-law response to high shear rate or stress.
Abstract: A film thickness correction for shear-thinning in rolling elastohydrodynamic (EHD) contacts has been available for about 8 years that uses parameters obtained from flow curves. Newly acquired shear-thinning data from experiment and simulation allow for a more narrow and more realistic range of parameters for ordinary lubricant base oils. Line contact film thickness calculations were performed over a wide range of conditions to arrive at a new film thickness correction that includes the sliding effect. This correction may be applied to any classical Newtonian prediction of film thickness for single-component liquids having ordinary power-law response to high shear rate or stress.
52 citations
TL;DR: In this article, the authors present results of a direct experimental test of the principal normal stress cavitation criterion (PNSCC) for low Reynolds number (Stokes) shear flows where reduction of the hydrodynamic pressure should not occur.
Abstract: Liquid failure has been observed in low Reynolds number (Stokes) shear flows where reduction of the hydrodynamic pressure should not occur. Cavitation in Stokes flows has implications in lubrication, polymer processing, and rheological measurements. Such cavitation can be predicted by a principal normal stress cavitation criterion (PNSCC). We present results of a direct experimental test of the PNSCC. Imaging of the cavitation events suggests that the cavitation is gaseous and originates from preexisting nuclei. Crevice-stabilized gas nuclei are assumed, and numerical simulations are used to investigate the cavitation event for a Newtonian liquid. The inception of cavitation from a preexisting nucleus, the persistence of suitable nuclei, and the growth and deformation of shed bubbles are considered. © 2005 American Institute of Chemical Engineers AIChE J, 2005
42 citations
TL;DR: The Rabinowitsch and Ferry models, with a second Newtonian viscosity incorporated in the usual way, can be an accurate description of this behavior and are convenient forms for integration into the Reynolds equation.
Abstract: A proper form of the Reynolds equation is lacking for the shear-thinning of polymer blended oil that displays a second Newtonian plateau. These multigrade lubricants respond linearly to shear stress at low stress, then follow a power-law at intermediate stress followed by linear response again at higher stress. The Rabinowitsch and Ferry models, with a second Newtonian viscosity incorporated in the usual way, can be an accurate description of this behavior and are convenient forms for integration into the Reynolds equation. The following one-dimensional Reynolds–Rabinowitsch equation has been derived for the Rabinowitsch double Newtonian model.
$$ {d\over dx} \left\{{p^{\prime} h^{3}\over 12\mu_{2}}- {{G^{2}-H^{2}}\over2\mu_2 p^{\prime 2}} \left[ \tau_m \ln \left( {H^2 + \tau_2^2}\over {H^2 +\tau_1^2}\right) - 2hp' + 2H \left( \tan^{-1} {{\tau^2}\over {H}} - \tan^{-1} {{\tau^1}\over{H}}\right) \right]\right\} = \bar{u} {{dh}\over {dx}}. $$
A Reynolds–Ferry double Newtonian equation has also been derived. Simple Grubin style solutions to the EHL line contact problem show that the new generalized Reynolds equations are accurate forms for double-Newtonian shear-thinning fluids.
14 citations
01 Jan 2005
TL;DR: In this article, an approximate Reynolds-Carreau equation was obtained from numerical solutions for flow rate, and an exact closed form one-dimensional Reynolds equation was presented for the Ostwald-DeWaele model, Ellis model, Spriggs model and double Newtonian Rabinowitsch and Ferry models.
Abstract: Exact, closed form one-dimensional Reynolds equations are presented for the Ostwald-DeWaele model, Ellis model, Spriggs model and the double-Newtonian Rabinowitsch and Ferry models. From numerical solutions for flow rate, an approximate Reynolds-Carreau equation is obtained.Copyright © 2005 by ASME
4 citations
01 Jan 2005
TL;DR: In this article, the shear response of the liquid in a parallel gap with a hemispherical pressure distribution was calculated to predict the elastic roller compliance for the small slide-to-roll ratio.
Abstract: Elastohydrodynamic point contact traction may be predicted accurately for the small slide-to-roll ratio, Σ, isothermal case by first calculating the shear response of the liquid in a parallel gap with a hemispherical pressure distribution and then correcting Σ for the elastic roller compliance.Copyright © 2005 by ASME
3 citations
2 citations
2 citations