The Behavior of an Elastohydrodynamic Lubricant at Moderate Pressures and High Shear Rates

1996 ◽  
Vol 118 (1) ◽  
pp. 162-168 ◽  
Author(s):  
Y. Zhang ◽  
K. T. Ramesh
Keyword(s):  
Shear Stress ◽  
Pressure Range ◽  
High Pressures ◽  
Shear Loading ◽  
Thin Layers ◽  
Experimental Results ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates ◽  
Wide Range

Knowledge of the behavior of lubricants over a wide range of pressures and shear rates is fundamental to an understanding of elastohydrodynamic (EHD) lubrication. The mechanical properties of elastohydrodynamic lubricants have been measured by a number of researchers under the conditions of low pressures and low shear rates, as well as under high pressures and high shear rates. This paper presents experimental results for the synthetic lubricant 5P4E subjected to moderate pressures (60 MPa to 700 MPa) and high shear rates (105 s−1) using the technique of pressure-shear plate impact. Thin layers (25 μm thick) of the lubricant are confined between two hard elastic plates; the assembly is subjected to impact by a parallel plate in a manner designed to induce both compression and shear loading. For approximately 1 μs the compressed lubricant is subjected to a simple shearing motion; during that time, continuous records of the shear stress and shear rate are obtained using laser interferometry. Three test configurations were used in order to cover the pressure range, and special techniques were developed for preparing the specimen sandwich. The pressure range covered includes both the liquid and glassy states of the lubricant. The results show that a limiting shear stress model is an appropriate model for lubricant behavior under these conditions. The experimental results also show little change in the lubricant shearing behavior across the glass transition.

Measurement of the viscosity of supercooled liquids at high shear rates with a Hopkinson torsion bar

1982 ◽  
Vol 381 (1780) ◽  
pp. 195-214 ◽  
Keyword(s):  
Shear Stress ◽  
High Pressures ◽  
Rolling Contact ◽  
Shear Strain Rate ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates ◽  
Short Time ◽  
Torsion Bar ◽  
Very High

The Eyring theory of viscous flow suggests that lubricating oils should exhibit shear thinning when the shear stress exceeds about 5 MPa. The results of friction experiments in rolling-contact disc machines where very high pressures are generated in the lubricant film support this prediction, but are open to the criticism that the fluid is subjected to a high pressure for such a short time ( ca . 10 -4 s) that an equilibrium state may not be reached. In the present investigation the appropriate condition of the lubricant is achieved, not by subjecting it to very high pressures but by maintaining it in the supercooled state. The lubricant is thus in a condition of equili­brium and the shear experiments are carried out at atmospheric pressure. The lubricant specimen is retained in a suitably adapted split Hopkinson torsion bar, and at the high rates of shear applied ( ca . 10 4 s -1 ) the shear stress at sufficiently low temperatures can exceed 5 MPa. By this tech­nique the shear pulse is applied for a sufficiently short time ( ca . 10 -3 s) to avoid viscous heating of the sample, which bedevils normal viscometry at high shear rates. Two fluids were tested: polyphenyl ether 5P4E and a mineral oil Shell HVI 650. Nonlinearity in the shear-stress-shear-strain-rate relation was found when the stress exceeded about 3 MPa. The elastic shear modulus G ∞ was also measured, yielding ca . 500 MPa for 5P4E and ca . 50 MPa for HVI 650.These values compare with ca . 1100 MPa and 300 MPa as found by the high-frequency oscillating shear technique at small strains.

A Pressure-Shear Plate Impact Experiment for Studying the Rheology of Lubricants at High Pressures and High Shearing Rates

1987 ◽  
Vol 109 (2) ◽  
pp. 215-222 ◽  
Author(s):  
K. T. Ramesh ◽  
R. J. Clifton
Keyword(s):  
Shear Stress ◽  
High Pressures ◽  
Laser Interferometry ◽  
Confining Pressure ◽  
Shear Loading ◽  
Thin Layers ◽  
Simple Shearing ◽  
Plate Impact ◽  
Shear Rates ◽  
Shearing Motion

A new plate impact configuration is described for subjecting lubricants to simple shearing motion under uniform hydrostatic pressure. Thin layers (∼50 μm thick) of the lubricant are confined between two hard metallic plates which are subjected to impact by a parallel plate that is inclined relative to the direction of approach in order to induce both pressure and shear loading. Stress waves in the hard plates are monitored by laser interferometry; all measurements are made before unloading waves arrive from the periphery. For approximately one microsecond the compressed lubricant is subjected to a simple shearing motion and a continuous record of the shear stress and shear rate is obtained. Results presented for the lubricant 5P4E at pressures of 1-5 GPa and shear rates of approximately 9 × 105 s−1 show good agreement with available data on the dependence of the limiting shear stress on the confining pressure at lower pressures and lower shearing rates.

A High Shear Rate Sliding Plate Rheometer for Nonlinear Viscoelasticity

2002 ◽  
Author(s):  
Gholamhossein Sodeifian ◽  
Ali Haghtalab ◽  
Amir Abdollah
Keyword(s):  
Shear Stress ◽  
Viscoelastic Properties ◽  
Nonlinear Viscoelasticity ◽  
Linear Actuator ◽  
High Shear ◽  
Shear Rates ◽  
System A ◽  
Nonlinear Viscoelastic ◽  
High Shear Rates ◽  
Sliding Plate

In most of polymer processings, such as injection molding and extrusion, materials are subjected to high deformations. In order to study nonlinear viscoelastic properties, it is necessary to have an instrument to generate high shear rates. A new sliding plate rheometer incorporating shear stress transducer has been developed. This rheometer has been equipped with a robust servohydraulic linear actuator which can generate shear rates and frequencies up to 900 (1/S) and 500 (Hz) respectively, compared with maximum 500 (1/S) and 100 (Hz), used in latest researches. Using this system, a wider range of nonlinear viscoelasticity can be investigated.

Effects of Temperature on Rheology of Olive Oils

2009 ◽  
Author(s):  
Nariman Ashrafi
Keyword(s):  
High Shear ◽  
Shear Rates ◽  
Olive Oils ◽  
High Shear Rates ◽  
Heating Effects ◽  
Wide Range ◽  
Minimum Viscosity ◽  
Sensory Changes ◽  
Effects Of Temperature ◽  
Insight Into

In this study, the rheological properties of different samples of olive oils, from the same producer were obtained in a wide range of temperature. At constant temperatures, the shear rate was also varied to obtain heating effects. It was found that all the samples reach a minimum viscosity in the temperature range of 120°C–150°C before thickening to higher viscosities. The viscosity remained almost unchanged in high shear rates regardless of temperature, indicating no shear thinning effects. No thixotropic effects were observed for the olive oils. These findings can provide insight into the microstructural, physiological and sensory changes at frying (high) temperatures.

THE SIGNIFICANCE OF FLOW-MODIFIED PERMITTIVITY: A NEW MODEL AND COMPUTER SIMULATION OF ELECTRORHEOLOGY

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2562-2568 ◽  
Author(s):  
YUE HU ◽  
EE-YENN E. LIN ◽  
UJITHA M. DASSANAYAKE
Keyword(s):  
Computer Simulation ◽  
Electric Field ◽  
Tilt Angle ◽  
Applied Electric Field ◽  
Dipole Moments ◽  
Chain Model ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates ◽  
Wide Range

We propose a model that takes into account the effect of flow-modified permittivity on electrorheology (ER). Due to dielectric relaxation, a shear flow causes the induced particle dipole moments in an ER fluid to tilt in a direction away from the direction of the applied DC electric field. Results from our computer simulation indicate that at high shear rates this misalignment (tilt angle) between the particle dipole moments and the applied electric field plays a crucial role in producing ER effects. By choosing particle-fluid dielectric and conductive mismatches to optimize the tilt angle, our simulation produces ER effects at much higher shear rates than those in earlier simulation work, even though there is no chain structure at these high shear rates. The increase in shear stress due to the applied electric field in our simulation is nearly constant over the wide range of shear rates examined, in qualitative agreement with experimental results. In addition, our model generates results that agree with earlier simulation work at low shear rates, where the particle dipole moments are essetially aligned with the field and the chain model is adequate.

Soluble Monomeric Von Willebrand Factor A1A2A3 (R1450E) Mutant Fragment Enhances Shear-Induced Platelet Aggregation and Platelet Adhesion to Fibrin(ogen) Via αIIbβ3 Under High Shear Stress.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4025-4025
Author(s):  
Miguel A. Cruz ◽  
Katie E. Sowa ◽  
Scott M. Smith
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Von Willebrand Factor ◽  
Platelet Adhesion ◽  
Surface Coverage ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Abstract 4025 Poster Board III-961 Recently, we described that the gain of function mutation R1450E in the A1 domain of von Willebrand factor (VWF) eliminates the formation of catch bond with glycoprotein (GP)Ibα, prolonging the bond lifetimes at low forces. Because those studies were performed with the mutant immobilized on a plastic surface, we further characterize the effect of this mutant on platelet function in solution and under shear stress. Both wild type (WT) and mutant A1A2A3 proteins were expressed in HEK293 cells and purified to homogeneity. The monomeric state of A1A2A3 proteins were assessed by gel filtration chromatography and neither of the proteins had formed dimers or any higher order aggregates. The recombinant A1A2A3 mutant bound spontaneously to GPIbα without the modulator ristocetin with a half-maximal binding observed at 65 ± 8 nM. This apparent dissociation constant was comparable to that of WT (50 ± 10 nM) in the presence of ristocetin. The mutant failed to induce spontaneous platelet aggregation under stirring conditions, and blocked 100% ristocetin-induced platelet agglutination (RIPA) at concentration of 250 nM. At the same concentration, the mutant increased shear-induced platelet aggregation (SIPA) at 500s-1 and 5000s-1 shear rates, reaching 42% and 66%, respectively, while SIPA did not exceed 18% in the presence of WT. The anti-αIIbβ3 antibody 7E3 blocked the effect of the mutant on SIPA. Blood was then incubated with the mutant (250 nM) and perfused over a surface coated with fibrin(ogen) at different shear rates. Blood containing WT resulted in <10% surface coverage by platelets after 1.5 minutes while platelets from blood containing the mutant rapidly bound covering 100% of the fibrin(ogen) surface area at 1500s-1. At shear rate of 2500s-1, surface coverage was 20% for the mutant and 0% for WT fragment. EDTA and antibodies 6D1 (GPIbα) and 10E5 (αIIbβ3) effectively blocked mutant-mediated platelet adhesion and thrombus formation under high shear rates. The addition of ristocetin (0.5 mg/ml) to whole blood prior perfusion reproduced the effect of the mutant. Here, we describe an A1A2A3 mutant that bound spontaneously to GPIbα but affected differently RIPA and SIPA. These results suggest that hydrodynamic forces directly act on the GPIbα-mutant A1A2A3 complex, regulating signaling. In addition, platelet activation induced by the binding of soluble mutant A1A2A3 or plasma VWF results in αIIbβ3-mediated platelet adhesion to fibrin(ogen) under high shear rates. Disclosures: No relevant conflicts of interest to declare.

Dynamic orientation transition of the lyotropic lamellar phase at high shear rates

Soft Matter ◽  
2015 ◽  
Vol 11 (48) ◽  
pp. 9330-9341 ◽  
Author(s):  
Shuji Fujii ◽  
Yuki Yamamoto
Keyword(s):  
Triblock Copolymer ◽  
Solvent Composition ◽  
Lamellar Phase ◽  
High Shear ◽  
Orientation Behavior ◽  
Shear Rates ◽  
High Shear Rates ◽  
Wide Range

The dynamic orientation behavior of the lamellar phase of a triblock copolymer is studied in a wide range of shear rates as a function of solvent composition.

scholarly journals Rheological Properties of Superparamagnetic Iron Oxide Nanoparticles

2021 ◽  
Vol 8 (1) ◽  
pp. C29-C37
Author(s):  
T. Javanbakht ◽  
S. Laurent ◽  
D. Stanicki ◽  
I. Salzmann
Keyword(s):  
Shear Stress ◽  
Iron Oxide ◽  
Shear Strain ◽  
Rheological Properties ◽  
Superparamagnetic Iron Oxide ◽  
Oxide Nanoparticles ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates ◽  
Positively Charged

The present study focuses on the rheological properties of polyethylene glycol (PEG) modified, positively charged, and negatively charged superparamagnetic iron oxide nanoparticles (SPIONs) at different temperatures. We hypothesized that the surface properties of these nanoparticles in the water did not affect their rheological properties. These nanoparticles had not the same surface properties as SPIONs-PEG had not to charge on their surface whereas positively charged and negatively charged ones with amine and carboxyl groups as their surfaces had positive and negative surface charges, respectively. However, their rheological behaviors were not different from each other. The comparative rheological study of SPIONs revealed their pseudo-Newtonian behavior. The viscosity of SPIONs decreased with the increase in temperature. At low shear rates, the shear stress of SPIONs was independent of rate and increased with the increase of rate. Moreover, at high shear rates, the shear stress for PEG-SPIONs was more than those for positively charged and negatively charged SPIONs. These measurements also revealed that at high shear rates, the shear stress of samples decreased with the increase of temperature. The shear stress of samples decreased with the increase of shear strain and the temperature. We also observed that all the samples had the same amount of shear strain at each shear stress, which indicated the exact resistance of SPIONs to deformation. Furthermore, the shear modulus decreased with time for these nanoparticles. These results suggest that these nanoparticles are promising candidates with appropriate properties for fluid processing applications and drug vectors in biomedical applications.

Relative Involvement of GPIb/IX-vWF Axis and GPIIb/IIIa in Thrombus Growth at High Shear Rates in the Guinea Pig

1997 ◽  
Vol 17 (5) ◽  
pp. 919-924 ◽  
Author(s):  
Patrick André ◽  
Patricia Hainaud ◽  
Claire Bal dit Sollier ◽  
Leonard I. Garfinkel ◽  
Jacques P. Caen ◽  
...  
Keyword(s):  
Guinea Pig ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates
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