scholarly journals Controlled shear stress method to measure yield stress of highly filled polymer melts

2016 ◽  
Author(s):  
Christian Kukla ◽  
Ivica Duretek ◽  
Clemens Holzer
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Polymer Melts ◽  
Filled Polymer

Rheology and structure of blood suspensions

1964 ◽  
Vol 19 (1) ◽  
pp. 127-133 ◽  
Author(s):  
S. E. Charm ◽  
W. McComis ◽  
G. Kurland
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Yield Stress ◽  
Structural Model ◽  
Cell Suspensions ◽  
Rate Curve ◽  
Red Cell ◽  
Shear Rates ◽  
Straight Line ◽  
Rate Plot

A structural model developed for kaolin suspensions was applied to blood in order to determine the structure and strength of the red cell suspensions. The yield stress of red cell suspensions determined in settling experiments agreed with the yield stress determined from shear stress-shear rate information employing Casson's equation. Theoretical considerations indicate that the shear stress-shear rate curve for blood should approach a straight line. This was found to be true at shear rates above 40 sec-1. The slope of this line was predicted from calculations based on sedimentation experiments and a modified Einstein's equation. The data suggest that the curvature of the shear stress-shear rate plot at low shear rates is due to aggregates of cells which break down under increasing shear rate, resulting finally in individual flocs. It is suggested that a floc consists of one to four cells with adhering plasma. The aggregate was calculated to have twice as much plasma associated with it as does a floc. However, the size of the aggregate could not be determined since the number of flocs associated with an aggregate could not be determined. shear stress-shear rate curve; red cell floc; red cell aggregate; sedimentation rate; blood viscosity and flow Submitted on February 28, 1963

Uniaxial elongational flow of particle-filled polymer melts

1998 ◽  
Vol 42 (3) ◽  
pp. 697-709 ◽  
Author(s):  
J. Greener ◽  
J. R. G. Evans
Keyword(s):  
Polymer Melts ◽  
Elongational Flow ◽  
Filled Polymer

Sensory Evaluation and Rheological Behavior of Commercial Mayonnaise

2007 ◽  
Vol 3 (1) ◽  
Author(s):  
Dayane Izidoro ◽  
Maria-Rita Sierakowski ◽  
Nina Waszczynskyj ◽  
Charles W. I. Haminiuk ◽  
Agnes de Paula Scheer
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Sensory Evaluation ◽  
Rheological Behavior ◽  
Oil Content ◽  
Sensory Attributes ◽  
Rheological Parameters ◽  
Low Fat ◽  
Concentric Cylinder ◽  
Rheological Characterization

The effects of ingredients on the sensory evaluation and rheological behavior of two brands of mayonnaise were examined in this work. Mayonnaise samples were examined by Analytical Descriptive Test and Ranking Test of Preference. The rheological parameters were determined at 25°C using a concentric cylinder Brookfield rheometer with a spindle SC4-34. The results showed that standard mayonnaise as opposed to low-fat mayonnaise gained higher grades for most sensory attributes. All samples were found to exhibit non-Newtonian pseudoplastic behavior described by Herschel–Bulkley model. A decrease in the yield stress, viscosity and shear stress with the decrease in oil content was observed in all products, which confirm that the rheological characterization is capable of distinguishing rather well between mayonnaises made with different formulation.

Flow Behaviors of Commercial Food Thickeners Used for the Management of Dysphagia: Effect of Temperature

2012 ◽  
Vol 8 (2) ◽  
Author(s):  
Se-Ra Hong ◽  
Dong-Soo Sun ◽  
Whachun Yoo ◽  
Byoungseung Yoo
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Flow Behavior ◽  
Effect Of Temperature ◽  
Rheological Parameters ◽  
High Shear ◽  
Flow Properties ◽  
Different Temperatures ◽  
Management Of Dysphagia ◽  
Arrhenius Temperature

Gum-based food thickeners are widely used to care for patients with dysphagia in Korea. In this study, the flow properties of commercially available gum-based food thickeners marketed in Korea were determined as a function of temperature. The flow properties of thickeners were determined based on the rheological parameters of the power law and Casson models. Changes in shear stress with the rate of shear (1-100 s-1) at different temperatures (5, 20, 35, and 50 oC) were independent of the type of thickener. All thickeners had high shear-thinning behavior (n=0.08-0.18) with yield stress at the different temperatures tested. In general, apparent viscosity (na,50) values progressively decreased with an increase in temperature. In addition, the consistency index (K) and Casson yield stress (σoc) values did not change much upon an increase in temperature from 5 to 35 oC, except for sample B. In the temperature range of 5-50 oC, the thickeners followed an Arrhenius temperature relationship with a high determination coefficient (R2=0.93-0.97): activation energies (Ea) for the flow of thickeners were in the range of 2.44 - 10.7 kJ/mol. Rheological parameters demonstrated considerable differences in flow behavior between the different gum-based food thickeners, indicating that their flow properties are related to the type of thickener and the flow properties of gum.

Pressure dependent wall slip of wood flour filled polymer melts

2017 ◽  
Vol 247 ◽  
pp. 178-187 ◽  
Author(s):  
Valentina Mazzanti ◽  
Francesco Mollica
Keyword(s):  
Polymer Melts ◽  
Wood Flour ◽  
Wall Slip ◽  
Filled Polymer

Off-Axis Torsion Tests on Tubular Specimens of Steel

2001 ◽  
Vol 123 (3) ◽  
pp. 268-273 ◽  
Author(s):  
Takenobu Takeda ◽  
Zhongchun Chen
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Maximum Shear Stress ◽  
Torsion Test ◽  
Combined Loading ◽  
Anisotropic Hardening ◽  
Principal Stresses ◽  
Maximum Value ◽  
The Difference ◽  
Tubular Specimens

In order to analyze the anisotropic hardening behavior of metals, an off-axis torsion test by combined loading is developed. In this test, the maximum shear stress direction φ can be changed from 0 deg to 90 deg while the ratio of maximum and minimum principal stresses is kept at −1. With increasing angle φ, the yield stress of the torsional-prestrained steel decreases; the difference between the directions of the maximum shear stress and principal shear strain increment rises to a maximum value and then decreases. It is experimentally verified that anisotropy is more severe when a smaller offset strain is used in defining the yield stress.

Is Radioactive Tank Waste a Bingham Fluid?

2019 ◽  
Author(s):  
Leonard F. Pease ◽  
Arich J. Fuher ◽  
Judith A. Bamberger ◽  
Carolyn A. Burns ◽  
Richard C. Daniel ◽  
...  
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Fluid Model ◽  
Bingham Fluid ◽  
Waste Processing ◽  
Rheological Models ◽  
Cross Model ◽  
Shear Rates ◽  
Sludge Waste ◽  
Tank Waste

Abstract Slurries and sludges across the United States Department of Energy (DOE) complex rank among the most rheologically interesting. Their composition is heterogeneous, spanning a very broad range of particle sizes, densities, and interparticle forces. All exhibit shear thinning, some have yield stresses, and many are thixotropic. Despite the variety, these complex fluids are often represented using the historic Bingham fluid model, which fits higher shear rate data to a simple straight line. The intercept provides a yield stress, which has been a key design parameter in construction of large-scale waste processing facilities. However, many radioactive wastes are simply not Bingham fluids, and this representation extrapolates poorly across low to intermediate shear rates that are characteristic of typical processing conditions. Indeed, processing shear rates as high as 200 1/s, which has been a typical minimum shear rate used in fitting the Bingham fluid model, are seldom encountered in nuclear waste processing. Therefore, more realistic rheological models are necessary to accurately predict waste processing performance. Pacific Northwest National Laboratory (PNNL) recently re-evaluated the rheology of reconstituted Hanford REDOX (reduction-oxidation) process sludge waste against a wide variety of rheological models including the Bingham, Cross, Cross with yield stress, Carreau, biviscous, Herschel-Bulkley (which includes a power law dependence), Casson, and Gay models. They found that all of the models provided a closer fit than the Bingham model and that the biviscous model and Cross with yield stress model were convincing. However, reconstituted Hanford REDOX sludge waste is but one type of DOE waste and a direct contrast, and comparison of these three models against undiluted, unmixed tank waste (actual not simulant) has not been performed previously. Therefore, the purpose of this paper is to evaluate the rheology of actual tank waste with these more accurate rheological models. In this paper, we evaluate select rheological data for slurry samples from Hanford’s AZ-101, AZ-102, and SY-101 waste tanks. In each of these cases, we find that Cross’ model with yield stress and the biviscous model significantly outperform the Bingham fluid model. Furthermore, the AZ-101 data also shows that the shear stress peak at startup significantly exceeds the Bingham yield stress, which is commonly observed in the initial moments of rheological measurements on simulants. Remarkably, Cross’ model may empirically accommodate an initial spike in shear stress at modest shear rates. These are important observations because computational and analytical fluid dynamics simulations rely on rheological constitutive models for accurately and conservatively predicting waste processing performance. These findings suggest the need for better rheological modeling of and validation against radioactive waste.

scholarly journals Pipe rheology of microfibrillated cellulose suspensions

Cellulose ◽  
2019 ◽  
Vol 27 (1) ◽  
pp. 141-156 ◽  
Author(s):  
Tuomas Turpeinen ◽  
Ari Jäsberg ◽  
Sanna Haavisto ◽  
Johanna Liukkonen ◽  
Juha Salmela ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Yield Stress ◽  
Power Law ◽  
Slip Flow ◽  
Microfibrillated Cellulose ◽  
Flow Index ◽  
Shear Rheology ◽  
Power Law Fluids ◽  
Wall Shear

Abstract The shear rheology of two mechanically manufactured microfibrillated cellulose (MFC) suspensions was studied in a consistency range of 0.2–2.0% with a pipe rheometer combined with ultrasound velocity profiling. The MFC suspensions behaved at all consistencies as shear thinning power law fluids. Despite their significantly different particle size, the viscous behavior of the suspensions was quantitatively similar. For both suspensions, the dependence of yield stress and the consistency index on consistency was a power law with an exponent of 2.4, similar to some pulp suspensions. The dependence of flow index on consistency was also a power law, with an exponent of − 0.36. The slip flow was very strong for both MFCs and contributed up to 95% to the flow rate. When wall shear stress exceeded two times the yield stress, slip flow caused drag reduction with consistencies higher than 0.8%. When inspecting the slip velocities of both suspensions as a function of wall shear stress scaled with the yield stress, a good data collapse was obtained. The observed similarities in the shear rheology of both the MFC suspensions and the similar behavior of some pulp fiber suspensions suggests that the shear rheology of MFC suspensions might be more universal than has previously been realized.

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