Controlled Shear Stress and Controlled Shear Rate Nonoscillatory Rheological Methodologies for Gelation Point Determination

AbstractThe rheological characterization of concentrated suspensions is complicated by the heterogeneous nature of their flow. In this contribution, the shear viscosity and wall slip velocity are quantified for highly concentrated suspensions (solid volume fractions of 0.55–0.60, D4,3 ~ 5 µm). The shear viscosity was determined using a high-pressure capillary rheometer equipped with a 3D-printed die that has a grooved surface of the internal flow channel. The wall slip velocity was then calculated from the difference between the apparent shear rates through a rough and smooth die, at identical wall shear stress. The influence of liquid phase rheology on the wall slip velocity was investigated by using different thickeners, resulting in different degrees of shear rate dependency, i.e. the flow indices varied between 0.20 and 1.00. The wall slip velocity scaled with the flow index of the liquid phase at a solid volume fraction of 0.60 and showed increasingly large deviations with decreasing solid volume fraction. It is hypothesized that these deviations are related to shear-induced migration of solids and macromolecules due to the large shear stress and shear rate gradients.

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Investigation on the Rheological Behavior of Polyamide6/Montmorillonite Nanocomposites by Reactive Extrusion

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.233-235.1998 ◽

2011 ◽

Vol 233-235 ◽

pp. 1998-2001 ◽

Cited By ~ 1

Author(s):

Ming Zhao ◽

Xiao Zhong Lu ◽

Kai Gu ◽

Xiao Min Sun ◽

Chang Qing Ji

Keyword(s):

Activation Energy ◽

Shear Stress ◽

Shear Rate ◽

Rheological Behavior ◽

Reactive Extrusion ◽

Shear Thinning ◽

Experimental Results ◽

Montmorillonite Nanocomposites

The rheological behavior of PA6/montmorillonite(MMT) by reactive extrusion was investigated using cone-and-plate rheometer. The experimental results indicated that PA6/MMT exhibited shear-thinning behavior. The shear stress of both neat PA6 and PA6/MMT increased with the increase in the shear rate. The reduction of the viscous activation energy with the increase of shear stress reflected PA6/MMT can be processed over a wider temperature.

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Are the dynamic response characteristics of brachial artery flow-mediated dilation sensitive to the magnitude of increase in shear stimulus?

Journal of Applied Physiology ◽

10.1152/japplphysiol.01190.2007 ◽

2008 ◽

Vol 105 (1) ◽

pp. 282-292 ◽

Cited By ~ 50

Author(s):

K. E. Pyke ◽

J. A. Hartnett ◽

M. E. Tschakovsky

Keyword(s):

Shear Stress ◽

Shear Rate ◽

Dynamic Response ◽

Phase I ◽

Brachial Artery ◽

Flow Mediated Dilation ◽

Final Phase ◽

Stimulus Magnitude ◽

Brachial Artery Diameter ◽

Response Characteristics

The purpose of this study was to determine the dynamic characteristics of brachial artery dilation in response to step increases in shear stress [flow-mediated dilation (FMD)]. Brachial artery diameter (BAD) and mean blood velocity (MBV) (Doppler ultrasound) were obtained in 15 healthy subjects. Step increases in MBV at two shear stimulus magnitudes were investigated: large (L; maximal MBV attainable), and small (S; MBV at 50% of the large step). Increase in shear rate (estimate of shear stress: MBV/BAD) was 76.8 ± 15.6 s−1 for L and 41.4 ± 8.7 s−1 for S. The peak %FMD was 14.5 ± 3.8% for L and 5.7 ± 2.1% for S ( P < 0.001). Both the L (all subjects) and the S step trials (12 of 15 subjects) elicited a biphasic diameter response with a fast initial phase (phase I) followed by a slower final phase. Relative contribution of phase I to total FMD when two phases occurred was not sensitive to shear rate magnitude ( r2 = 0.003, slope P = 0.775). Parameters quantifying the dynamics of the FMD response [time delay (TD), time constant (τ)] were also not sensitive to shear rate magnitude for both phases (phase I: TD r2 = 0.03, slope P = 0.376, τ r2 = 0.04, slope P = 0.261; final phase: TD r2 = 0.07, slope P = 0.169, τ r2 = 0.07, slope P = 0.996). These data support the existence of two distinct mechanisms, or sets of mechanisms, in the human conduit artery FMD response that are proportionally sensitive to shear stimulus magnitude and whose dynamic response is not sensitive to shear stimulus magnitude.

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Effect of Shear Surface Boundaries on Stress for Shearing Flow of Dry Metal Powders—An Experimental Study

Journal of Tribology ◽

10.1115/1.3261343 ◽

1987 ◽

Vol 109 (2) ◽

pp. 232-237 ◽

Cited By ~ 39

Author(s):

K. Craig ◽

R. H. Buckholz ◽

G. Domoto

Keyword(s):

Shear Stress ◽

Shear Rate ◽

Normal Stress ◽

Particle Diameter ◽

Surface Boundary ◽

Metal Powders ◽

Shear Surface ◽

Shear Cell ◽

Shearing Flow ◽

Solids Content

This paper studies the rapid simple shearing flow of dry cohesionless metal powders contained between parallel rotating plates. In this study, an annular shear cell test apparatus was used; the dry metal powders are rapidly sheared by rotating one of the shear surfaces while the other shear surface remains fixed. Such a flow geometry is of interest to tribologists working in the area of dry or powder lubrication. The shear stress and normal stress on the stationary surface are measured as a function of the following parameters: shear surface boundary material and roughness, the shear-cell gap thickness, the shear-rate and the fractional solids content. Both the fractional solids content and the gap thickness are kept at prescribed values during stress measurements. In this experiment the metal powder tested is different from the shear transmission surface material; the effect on the measured normal and shear stress data are reported. The results show the dependence of the normal stress and the shear stress on the shear-rate, particle density and particle diameter. Likewise, a significant stress dependence on both the fractional solids content and the shear-cell gap thickness was observed.

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Investigation of the Sedimentation Property of Backfill Material on the Basis of Rheological Test: A Case Study of Iron Tailings

Journal of Chemistry ◽

10.1155/2018/9530767 ◽

2018 ◽

Vol 2018 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Yong Wang ◽

Aixiang Wu ◽

Lianfu Zhang ◽

Hongjiang Wang ◽

Fei Jin

Keyword(s):

Shear Stress ◽

Shear Rate ◽

Mass Concentration ◽

Filling Material ◽

Quantitative Characterization ◽

Filling Materials ◽

Characterization Studies ◽

Rheological Test ◽

Sedimentation Property

Sedimentation of filling materials could cause pipe blocking accident in mines. However, few quantitative characterization studies have investigated the sedimentation characteristics of filling materials. In this study, the sedimentation property of iron tailings with a cement-sand ratio of 1 : 4 and mass concentration of 73%∼82% was investigated based on rheology measurements. Results showed that shear stress increased as shear rate rose from 0 s−1to 120 s−1. The shear stress increased as the filling material concentration increased as well. However, when the shear rate was reversed from 120 s−1to 0 s−1, the shear stress presented an increase-constant-decrease change pattern as the mass concentration increases in the rheological curve. Accordingly, the sedimentation performance of iron tailings filling material was divided into three types: intense sedimentation (the ascending rheological curve) in the mass concentration range of 73%∼76%, slight sedimentation (the constant rheological curve) in the mass concentration range of 77%∼79%, and almost no sedimentation (the descending rheological curve) in the mass concentration range of 80%∼82%. The associated mechanism involving slurry mass concentration-rheological curves-sedimentation performance was illustrated. A correlation between the pipeline rheology and filling material sedimentation performance was established, which provides a practical guide to avoid pipeline blocking while transporting the filling material.

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ENTROPY INFLUENCE ON THE DEPENDENCE OF THE NANOFLUIDS VISCOSITY ON TEMPERATURE AND SHEAR RATE

Tyumen State University Herald Physical and Mathematical Modeling Oil Gas Energy ◽

10.21684/2411-7978-2021-7-3-89-105 ◽

2021 ◽

Vol 7 (3) ◽

pp. 89-105

Author(s):

Lyudmila P. SEMIKHINA ◽

Daniil D. Korovin

Keyword(s):

Activation Energy ◽

Shear Stress ◽

Shear Rate ◽

Viscous Flow ◽

High Reliability ◽

Narrow Particle Size Distribution ◽

Disperse Systems ◽

Rotational Viscometer ◽

Surfactant Micelles ◽

Dispersed Systems

A Brookfield DV-II + Pro rotational viscometer was used to study the viscosity of 7 samples of concentrated nanodispersed systems (nanofluids) with a similar viscosity (6-22 mPa ∙ s), the particles of the dispersed phase in which are nanosized surfactant micelles and conglomerates from them. It was found that for 5 out of 7 studied reagents, there is a decrease in viscosity typical for dispersed systems with an increase in the shear rate, and their flow curves, that is, the dependence of the shear stress on the shear rate, correspond to the ideal plastic flow of non-Newtonian fluids. Moreover, with high reliability, R2 ≥ 0.999 is described by the Bingham equation with a small value of the limiting shear stress (less than 0.2 Pa). It is shown that all the studied reagents are also characterized by an increase in the activation energy of a viscous flow Е with an increase in the shear rate. As a result, a decrease in viscosity with an increase in shear rate, typical for disperse systems, including nanofluids, is provided by a more significant increase in entropy changes ΔS compared to Е. It has been substantiated that, depending on the ratio between the activation energy of viscous flow Е and the change in entropy ΔS, the viscosity of concentrated micellar dispersed systems with an increase in the shear rate can decrease, remain unchanged, and increase. The last two cases, not typical for disperse systems and nanofluids, were identified and studied using the example of two demulsifiers, RIK-1 and RIK-2, with a maximum of a very narrow particle size distribution at 160 ± 5 nm, corresponding to the size of a special type of very stable micelles Surfactant — vesicle.

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Flow Properties of Utah Shale Oils

Society of Petroleum Engineers Journal ◽

10.2118/9500-pa ◽

1981 ◽

Vol 21 (06) ◽

pp. 679-686 ◽

Cited By ~ 1

Author(s):

W.H. Seitzer

Keyword(s):

Shear Stress ◽

Shear Rate ◽

Pour Point ◽

Water Solution ◽

Shale Oil ◽

Concentric Cylinder ◽

Long Distance ◽

Time Calibration ◽

The Difference ◽

Cylinder Viscometer

Abstract In a concentric cylinder viscometer. Utah shale oils have different characteristics, both at equilibrium flow and during start-up from rest, depending on whether the wax has crystallized as needles or spherulites. Compared with waxy crude oils, which are thixotropic, shale oil had the added rheological property of being antithixotropic. Introduction The most likely liquid synthetic fuel to be produced initially in the U.S. will be raw shale oil from western oil shale. This abundant resource is located principally in the western Rocky Mountain states of Colorado. Utah. and Wyoming (Fig. 1). Ultimate commercial production probably will be transported to marketing, distribution, and refining centers by pipeline. It has been reported that Utah shale oils produced by the Union "B" and Paraho DH retorting processes gave similar physical and chemical properties. Some properties of the two Utah shale oils are given in Table 1. The only major difference is that the Union shale oil has a pour point of - 1 degree C compared with a pour point of 25 degrees C for the Paraho oil. Wax Crystallization The difference in the pour points of the oils from the Utah shale retorted by Union Oil Co of California and Paraho is caused mainly by the difference in how the wax in the respective oils crystallizes. In the high- pour-point (25 degrees C) Paraho DK oil, the wax, under a microscope, appears as fine (1 to 10 m) needles, as expected for normal paraffins. However, the wax in the low-pour-point (−1 degrees C) Union oil forms small spherulites.Wax spherulites have not been reported before: however, this type of crystal is seen commonly in polymer. Spherulites show up as round areas containing a maltese cross when observed between crossed polars under a microscope.Photomicrographs of these crystals are shown in Figs. 2 and 3. The former, showing spherulites, is of the Union oil. In contrast, they are very different from the customary needles as typified by the Paraho oil in the latter micrograph. Presumably, these highly ordered spheres are made up of wax needles grown out radially from the center as described by Hartshorne and Stuart. The polarized light is scattered only by those needles not parallel nor perpendicular to the plane of polarization. Viscometer Measurements To understand the effect of these spherulites on the flow characteristics of raw shale oil at flow conditions expected in a long-distance pipeline, typical stress-rate measurements were made in a rotating cylinder viscometer, the Haake Rotovisco RV3 with MK500 measuring head and MVI coaxial cylinder sensor having an 82-mm cup and radii ratio of 0.95. This equipment has provisions for varying shear rate continuously at selected values down to 23.4 sec(−1)/min and can produce and record shear stress as a function of either shear rate or time. Calibration of the sensor was verified with a sucrose/water solution at several temperatures.Changes in temperature always were made from lower to higher to keep the sensor full of oil. Also, the shear-stress/ shear-rate curves were obtained by starting at high shear, down to zero, and then back up. SPEJ P. 679^

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Shear-rate dependence of thermodynamic properties of the Lennard-Jones truncated and shifted fluid by molecular dynamics simulations

10.31219/osf.io/6w5bc ◽

2021 ◽

Author(s):

Martin P. Lautenschlaeger ◽

Hans Hasse

Keyword(s):

Molecular Dynamics ◽

Shear Stress ◽

Shear Rate ◽

Molecular Dynamics Simulations ◽

Local Structure ◽

Rate Dependence ◽

Lennard Jones ◽

Fluid Properties ◽

Dynamics Simulations ◽

Shear Rate Dependence

It was shown recently that using the two-gradient method, thermal, caloric, and transport properties of fluids under quasi-equilibrium conditions can be determined simultaneously from nonequilibrium molecular dynamics simulations. It is shown here that the influence of shear stresses on these properties can also be studied using the same method. The studied fluid is described by the Lennard-Jones truncated and shifted potential with the cut-off radius r*c = 2.5σ. For a given temperature T and density ρ, the influence of the shear rate on the following fluid properties is determined: pressure p, internal energy u, enthalpy h, isobaric heat capacity cp, thermal expansion coefficient αp, shear viscosity η, and self-diffusion coefficient D. Data for 27 state points in the range of T ∈ [0.7, 8.0] and ρ ∈ [0.3, 1.0] are reported for five different shear rates (γ ̇ ∈ [0.1,1.0]). Correlations for all properties are provided and compared with literature data. An influence of the shear stress on the fluid properties was found only for states with low temperature and high density. The shear-rate dependence is caused by changes in the local structure of the fluid which were also investigated in the present work. A criterion for identifying the regions in which a given shear stress has an influence on the fluid properties was developed. It is based on information on the local structure of the fluid. For the self-diffusivity, shear-induced anisotropic effects were observed and are discussed.

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Research on the Mechanism of Surfactant Warm Mix Asphalt Additive-Based on Molecular Dynamics Simulation

Coatings ◽

10.3390/coatings11111303 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1303

Author(s):

Pinhui Zhao ◽

Mingliang Dong ◽

Yansheng Yang ◽

Jingtao Shi ◽

Junjie Wang ◽

...

Keyword(s):

Molecular Dynamics ◽

Shear Stress ◽

Shear Rate ◽

Asphalt Binder ◽

Warm Mix Asphalt ◽

Dynamics Simulation ◽

Stone Surface ◽

Lubricating Film ◽

Lubrication Performance ◽

Shear Friction

Warm mix asphalt (WMA) technology can bring certain environmental and technical benefits through reducing the temperature of production, paving, and compaction of mixture asphalt. Recent studies have shown that some WMA additives are able to reduce the temperature by increasing the lubricating properties of asphalt binder.-based on the tribological theory, this paper studied the mechanism of adsorbing and lubricating film of base asphalt and WMA on the surface of stone by molecular dynamics (MD) simulation method, and the effect of surfactant WMA additive on the lubrication performance of the shear friction system of “stone–asphalt–stone”. The model of base asphalt lubricating film, including saturates, aromatics, resin and asphaltene, as well as the model of warm mix asphalt lubricating film containing imidazoline-type surfactant WMA (IMDL WMA) additive molecule, were established. The shear friction system of “stone–asphalt–stone” of base asphalt and warm mix asphalt was built on the basis of an asphalt lubrication film model and representative calcite model. The results show that the addition of IMDL WMA additive can effectively improve the lubricity of asphalt, reduce the shear stress of asphalt lubricating film, and increase the stability of asphalt film. The temperature in the WMA lubricating film rises, while the adsorption energy on the stone surface decreases with the increase of shear rate, indicating that the higher the shear rate is, the more unfavorable it is for the WMA lubricating film to wrap on the stone surface. In addition, the shear stress of the WMA lubricating film decreased with increasing temperature, while the shear stress of the base asphalt lubricating film increased first and then decreased, demonstrating that the compactability of the asphalt mixture did not improve linearly with the increase of temperature.

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The influence of base oil type on the rheological properties of ecological lubricating greases

Nafta-Gaz ◽

10.18668/ng.2021.02.07 ◽

2021 ◽

Vol 77 (2) ◽

pp. 127-135

Author(s):

Rafał Kozdrach ◽

Keyword(s):

Shear Stress ◽

Shear Rate ◽

Rheological Properties ◽

Measurement Data ◽

Measuring System ◽

Rheological Parameters ◽

Flow Curves ◽

Lubricating Grease ◽

Dispersion Phase ◽

Base Oil

The article presents the results of research on the influence the type of base oil in lubricating compositions has on the rheological parameters of selected lubricants. Vegetable, mineral, and synthetic dispersion phases were used to produce lubricating greases. The modified amorphous silica was used as the dispersed phase. However, as a modifying additive was used a substance containing the antioxidants, corrosion inhibitors, and EP/AW additives. The experiments on rheological properties were carried out using a Physica MCR 101 rotational rheometer (manufactured by Anton Paar), equipped with a diffusion air bearing and connected to a pneumatic supply – an oil-free Jun-Air compressor and air drying block. The device is equipped with a Peltier system for temperature control in the range of –20°C to 200°C and an external thermostatic VISCOTHERM V2 system, working in the temperature range of –20°C to 200°C. The rheometer control and measurement data analysis were performed using Rheoplus software. The tests were carried out using a cone-plate measuring system with a shear rate range of 0.01–100 s-1 at 20°C for lubricating compositions prepared on various oil bases. To evaluate the value of rheological parameters, the results of tests of the dependence between shear stress and shear rate (flow curves) were used. For the theoretical determined on the flow curves, the following rheological models were used: Bingham, Herschel–Bulkley, Casson, and Tscheuschner. The values of the shear stress (yield point) in depending on the type of dispersion phase has changed. This proves that the use of a base oil with the appropriate functional properties does not weaken, but reinforces the spatial structure of a lubricating grease. It has an important meaning when selecting construction parameters when designing a central lubrication system with grease made from a vegetable oil base (Abyssinian oil). The rheological properties of the lubricating grease are influenced by the type of base oil and thickener, any additives in the grease, the production technology of the grease, and the conditions in which it is used. The tests revealed an important influence of the base oil on the rheological parameters that describe the behaviour of lubricating compositions subjected to stresses and strains in a lubricating system.

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