scholarly journals An alternative approach for measuring yield stress and its application in Carbopol microgel

2021 ◽  
Vol 60 (2-3) ◽  
pp. 141-154
Author(s):  
Vincenzo Iannotti ◽  
Luca Lanotte ◽  
Giovanna Tomaiuolo ◽  
Giovanni Ausanio ◽  
Raffaele Graziano ◽  
...  
Keyword(s):  
Yield Stress ◽  
Relaxation Effect ◽  
Equilibrium Equations ◽  
Magnetic Induction Field ◽  
Alternative Approach ◽  
Experimental Apparatus ◽  
Shear Yield ◽  
Complex Fluid ◽  
Elastic Reaction ◽  
Shed Light

AbstractAn innovative experimental apparatus for the direct measurement of yield stress was conceived and realized. It is based on a torsion pendulum equipped with a magnetic dipole and a rotating cylinder immersed in the material to be investigated. The pendulum equilibrium state depends on the mechanical torque applied due to an external magnetic induction field, elastic reaction of the suspension wire, and shear yield stress. Experimental results are reported showing that the behavior of the pendulum rotation angle, in different equilibrium conditions, provides evidence of the yield stress presence and enables its evaluation by equilibrium equations. The dependence on time of the equilibrium approach was also studied, contributing to shed light on the relaxation effect in the transition from a fluid-like to solid-like behavior, as well as on the eventual thixotropic effects in non-Newtonian fluids. The validity of the proposed technique and related experimental apparatus was tested in aqueous Carbopol solutions, with different weight percentages. The linear procedure, combined with the effectiveness and reliability of the proposed experimental method, candidates it to be used for the study of peculiar behaviors of other yield stress complex fluid such as blood, crude waxy oils, ice slurries, and coating layer used in the food industry and also for fault sliding in geodynamics.

The shear and compressive yield stress of fibrillated acacia pulp fiber suspensions

2020 ◽  
Vol 35 (2) ◽  
pp. 243-250
Author(s):  
Jiulong Sha ◽  
Yueyue Yang ◽  
Can Wang ◽  
Wei Li ◽  
Peng Lu ◽  
...  
Keyword(s):  
Yield Stress ◽  
Paper Industry ◽  
Pulp Fiber ◽  
Fiber Suspensions ◽  
Fiber Morphology ◽  
Shear Yield Stress ◽  
Geometrical Properties ◽  
Compressive Yield Stress ◽  
Shear Yield ◽  
Fiber Cell Wall

AbstractThe degree of interactions between fibers and the tendency of fibers to form flocs play an important role in effective unit operation in pulp and paper industry. Mechanical treatments may damage the structure of the fiber cell wall and geometrical properties, and ultimately change the fiber-fiber interactions. In this study, the gel crowding number, compressive and shear yield stress of fibrillated acacia pulps were investigated, and the results showed that the gel crowding number of the refined pulp samples ranged from 8.7 to 10.7, which were much lower than that of un-refined pulps. As the concentration increased, both the compressive yield stress {P_{y}} and shear yield stress {\tau _{y}} of all suspensions increased accordingly, and the yield stress was found to depend on a power law of the crowding number. Moreover, the values of {\tau _{y}}/{P_{y}} were also examined and the variation of {\tau _{y}}/{P_{y}} became largely dependent on the fiber morphology and mass concentration.

Shear yield stress of partially flocculated colloidal suspensions

AIChE Journal ◽  
1998 ◽  
Vol 44 (3) ◽  
pp. 538-544 ◽  
Author(s):  
Peter J. Scales ◽  
Stephen B. Johnson ◽  
Thomas W. Healy ◽  
Prakash C. Kapur
Keyword(s):  
Yield Stress ◽  
Colloidal Suspensions ◽  
Shear Yield Stress ◽  
Shear Yield

Demonstration of Combined Shear and Squeeze Strengthening Modes in a Searle-Type Magnetorheometer

2013 ◽  
Author(s):  
Andrew C. Becnel ◽  
Norman M. Wereley
Keyword(s):  
Yield Stress ◽  
Energy Absorption ◽  
Shear Yield Stress ◽  
Particle Chain ◽  
Solids Loading ◽  
Mr Fluids ◽  
Shear Yield ◽  
Microstructure Model ◽  
Novel Method ◽  
A Chain

This research details a novel method of increasing the shear yield stress of magnetorheological (MR) fluids by combining shear and squeeze modes of operation to manipulate particle chain structures, to achieve so-called compression-assisted aggregation. The contribution of both active gap separation and particle concentration are experimentally measured using a custom-built Searle cell magnetorheometer, which is a model device emulating a rotary Magnetorheological Energy Absorber (MREA). Characterization data from large (1 mm) and small (250 μm) gap geometries are compared to investigate the effect of the gap on yield stress by compression enhancement. Two MR fluids having different particle concentrations (32 vol% and 40 vol%) are also characterized to demonstrate the effect of solids loading on compression-assisted chain aggregation. Details of the experimental setup and method are presented, and a chain microstructure model is used to explain experimental trends. The torque resisted by practical rotary MREAs is directly related to the strength of the MR fluid used, as measured by the shear yield stress. This study demonstrates that it is feasible, utilizing the compression-enhanced shear yield stress, to either (1) design a rotary MREA of a given volume to achieve higher energy absorption density (energy absorbed normalize by device volume), or (2) reduce the volume of a given rotary MREA to achieve the same energy absorption density.

Compression Enhanced Shear Yield Stress of Electrorheological Fluid

2009 ◽  
Vol 26 (4) ◽  
pp. 048301 ◽  
Author(s):  
Zhang Min-Liang ◽  
Tian Yu ◽  
Jiang Ji-Le ◽  
Zhu Xu-Li ◽  
Meng Yong-Gang ◽  
...  
Keyword(s):  
Yield Stress ◽  
Electrorheological Fluid ◽  
Shear Yield Stress ◽  
Shear Yield

Effect of annealing on the shear yield stress of rejuvenated polycarbonate

Polymer ◽  
1988 ◽  
Vol 29 (11) ◽  
pp. 1985-1989 ◽  
Author(s):  
C. Bauwens-Crowet ◽  
J-C. Bauwens
Keyword(s):  
Yield Stress ◽  
Shear Yield Stress ◽  
Shear Yield

Behavior of a Compressible Magnetorheological Fluid Damper at High Temperatures

2011 ◽  
Author(s):  
Micheal McKee ◽  
Xiaojie Wang ◽  
Faramarz Gordaninejad
Keyword(s):  
Theoretical Model ◽  
Bulk Modulus ◽  
Yield Stress ◽  
Magnetorheological Fluid ◽  
Effect Of Temperature ◽  
Temperature Dependent ◽  
Bingham Plastic ◽  
Shear Yield ◽  
Fluid Dampers ◽  
Temperature Dependent Properties

This study focuses on the effect of temperature on the performance of compressible magnetorheological fluid dampers (CMRDs). In addition to change of properties in the presence of a magnetic field, magnetorheological fluids (MRFs) are temperature-dependent materials that their compressibility and rheological properties change with temperature, as well. A theoretical model that incorporates the temperature-dependent properties of MRF is developed to predict the behavior of a CMRD. An experimental study is also conducted using an annular flow CMRD with varying temperatures, motion frequencies, and magnetic fields. The experimental results are used to verify the theoretical model. The effect of temperature on the MRF properties, such as, the bulk modulus, yield stress and viscosity, are explored. It is found that the shear yield stress of the MRF remains unchanged within the testing range while both the plastic viscosity, using the Bingham plastic model, and the bulk modulus of the MRF decrease as temperature increases. In addition, it is observed that both the stiffness and the energy dissipation decrease with an increase in temperature.

scholarly journals Preliminary experimental evaluation of a novel loudspeaker featuring magnetorheological fluid surround absorber

2020 ◽  
Vol 17 (2) ◽  
pp. 922 ◽  
Author(s):  
Endra Dwi Purnomo ◽  
Ubaidillah Ubaidillah ◽  
Fitrian Imaduddin ◽  
Iwan Yahya ◽  
Saiful Amri Mazlan
Keyword(s):  
Magnetic Flux ◽  
Yield Stress ◽  
Experimental Evaluation ◽  
Flux Distribution ◽  
Magnetic Circuit ◽  
Experimental Result ◽  
The Finite Element Method ◽  
Shear Yield Stress ◽  
Shear Yield ◽  
Novel Design

<span>A novel design of magnetorheological fluids (MRF) based surround device in a loudspeaker system was studied in this article. The main objective of this research is to design a new surround device of the loudspeaker that can be easily controlled its damping. Therefore, it was predicted that the audio pressure level on the loudspeaker could be easily manipulated at a different sound source by applying a certain magnetic field. This function could not be reached using one conventional speaker system. Firstly, a set of an electromagnetic device containing MRF was designed to replace the conventional rubber surround. The magnetic circuit was then evaluated using the finite element method magnetics to study the flux distribution in the MRF area. The current was varied from 0.25 to 0.75 A by an interval of 0.25 A. The magnetic flux resulted from the simulation was then logged and used as the based value for predicting the change of shear yield stress. The base properties of the shear yield stress of the MRF against the magnetic flux was obtained from previous experimental result. Therefore, it was hopefully the prediction could be closed to the real system. Based on the simulation result, the shear yield stress varied from 43 to 49 Mpa or about 15 % increment. </span><span lang="IN">A simple experimental work was carried out. By applying particular direct current into the coil, the sound quality generated by the loudspeaker shows different values</span><span>.</span><span lang="IN"> Based on the preliminary experiment, the level of decibel decreased about 3 dB as the application of magnetic fields. The idea has been proven in this preliminary experimental evaluation.</span>

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