Normalized Ashurst-Hoover Scaling and a Comprehensive Viscosity Correlation for Compressed Liquids

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Scott Bair ◽  
Arno Laesecke
Keyword(s):  
Free Volume ◽  
Essential Requirement ◽  
New Correlation ◽  
Wide Acceptance ◽  
Viscosity Correlation ◽  
Low Shear Viscosity ◽  
Temperature And Pressure ◽  
Exponential Power ◽  
Volume Models ◽  
Low Shear

The recent move toward physics-based elastohydrodynamics promises to yield advances in the understanding of the mechanisms of friction and film generation that were not possible a few years ago. However, the accurate correlation of the low-shear viscosity with temperature and pressure is an essential requirement. The Ashurst-Hoover thermodynamic scaling, which has been useful for thermal elastohydrodynamic simulation, is normalized here in a manner that maps the viscosity of three widely different liquids onto a master Stickel curve. The master curve can be represented by a combination of two exponential power law terms. These may be seen as expressions of different molecular interaction mechanisms similar to the two free-volume models of Batschinski-Hildebrand and Doolittle, respectively. The new correlation promises to yield more reasonable extrapolations to extreme conditions of temperature and pressure than free-volume models, and it removes the singularity that has prevented wide acceptance of free-volume models in numerical simulations.

The Viscosity of Polyalphaolefins Mixtures at High Pressure and Stress

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Scott Bair ◽  
Samuel Flores-Torres
Keyword(s):  
High Pressure ◽  
Shear Stress ◽  
Film Thickness ◽  
Shear Viscosity ◽  
Mixing Rule ◽  
Base Oils ◽  
Film Forming ◽  
Low Shear Viscosity ◽  
Temperature And Pressure ◽  
Low Shear

Understanding the pressure and shear dependence of viscosity is essential to an understanding of the mechanisms of film forming and friction in concentrated contacts. The blending of different molecular mass polyalphaolefins (PAOs) may permit the formulator to arrive at a desired combination of film thickness and friction. The viscosities of PAO base oils and their blends were measured versus temperature, pressure, and shear stress to 1 GPa in pressure. The Grunberg–Nissan mixing rule, with effective mole fractions, provides an excellent mixing rule for the temperature and pressure-dependent low-shear viscosity. This work provides the first look at a possible mixing rule for the non-Newtonian response of mixtures of base oils.

Low shear viscosity of polypropylene melts

1963 ◽  
Vol 1 (7) ◽  
pp. 381-384 ◽  
Author(s):  
D. Poller ◽  
A. M. Kotliar ◽  
R. L. Kruse
Keyword(s):  
Shear Viscosity ◽  
Low Shear Viscosity ◽  
Low Shear

The Equation of State and the Temperature, Pressure, and Shear Dependence of Viscosity for a Highly Viscous Reference Liquid, Dipentaerythritol Hexaisononanoate

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Scott Bair ◽  
Tsuyoshi Yamaguchi
Keyword(s):  
Molecular Weight ◽  
Shear Stress ◽  
Equation Of State ◽  
High Molecular Weight ◽  
Free Volume ◽  
Newtonian Limit ◽  
Scaling Models ◽  
The Difference ◽  
Better Than ◽  
Low Shear

Measurements are reported for dipentaerythritol hexaisononanoate (DiPEiC9) of pressure–volume–temperature (pVT) response to pressures to 400 MPa and temperatures to 100 °C, and of viscosity at pressures to 700 MPa and temperatures to 90 °C and shear stress to 18 MPa. These data complement the low-shear viscosities published by Harris to pressures to 200 MPa and the compressions by Fandiño et al. to 70 MPa. The improved Yasutomi correlation reproduces all viscosity measurements with accuracy better than the Doolittle free volume and the Bair and Casalini thermodynamic scaling models which require an equation of state (EoS). The interaction parameter for thermodynamic scaling, γ = 3.6, is less than that reported by Harris (γ = 4.2) and the difference is primarily in the choice of EoS. The shear stress at the Newtonian limit, about 6 MPa, is exceptionally large given the high molecular weight of DiPEiC9. The large Newtonian limit is also seen in the oscillatory shear response.

Dispersion and Rheological Properties of Alumina Freeze Casting Slurries Containing Nanoparticle/Whisker SiC

2007 ◽  
Vol 280-283 ◽  
pp. 1035-1038 ◽  
Author(s):  
Tae Young Yang ◽  
Young Min Park ◽  
Gun Dae Lee ◽  
Seog Young Yoon ◽  
Ron Stevens ◽  
...  
Keyword(s):  
Shear Rate ◽  
Shear Viscosity ◽  
Pure Alumina ◽  
Rheological Measurements ◽  
Continuous Shear ◽  
Suspension Viscosity ◽  
Low Shear Viscosity ◽  
Opposite Manner ◽  
High Structure ◽  
Low Shear

The sedimentation density significantly decreased after addition of dispersant; the effect was more pronounced with pure alumina, as compared with SiC-containing slurry. With further addition of surfactant, the sedimentation density increased somewhat, but decreased with binderadditions. The suspension viscosity generally behaved in an opposite manner to the sedimentation density, i.e., low sedimentation density gave high low-shear viscosity, indicative of high structure formation in the suspended particles. Shear rate rheological measurements showed continuous shear thinning behavior.

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