THE STRENGTH OF ELECTRORHEOLOGICAL (ER) FLUIDS

1992 ◽  
Vol 06 (15n16) ◽  
pp. 2575-2594 ◽  
Author(s):  
H. CONRAD ◽  
Y. CHEN ◽  
A. F. SPRECHER
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Enhancement Factor ◽  
Reasonable Agreement ◽  
Force Enhancement ◽  
Single Row ◽  
Field Temperature ◽  
Definition Of ◽  
Er Fluids ◽  
Er Fluid

The definition of the strength of an ER fluid is discussed. Studies on the electrorheology of ER fluids containing zeolite particles in various oils indicate that the order of magntiude difference between the measured values of the yield stress and those calculated based on the axial force of interaction between particles in a single-row chain can be explained by an enhancement of the force due to the observed clustering of particles into multi-row chains. The force enhancement factor varied with the shear rate and the concentration of particles, but was relatively independent of the electric field, temperature and host fluid. Reasonable agreement existed between the predicted and the measured shear stress-shear strain curves and the concentration dependence of the yield stress when the appropriate force enhancement factor was taken into account. The present theoretical-experimental considerations suggest that ER fluids may attain a yield strength of ~ 50 kPa .

POLAR-MOLECULE-DOMINATED ELECTRORHEOLOGICAL (PM-ER) FLUIDS: THE PROPERTIES AND EVALUATIONS

2011 ◽  
Vol 25 (07) ◽  
pp. 957-962 ◽  
Author(s):  
KUNQUAN LU ◽  
RONG SHEN ◽  
XUEZHAO WANG ◽  
DE WANG ◽  
GANG SUN
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Yield Stress ◽  
Linear Dependence ◽  
Polar Molecule ◽  
High Yield ◽  
Electric Response ◽  
New Type ◽  
Er Fluids ◽  
Er Fluid

In recent years, a new type ER fluids named as polar-molecule-dominated electrorheological (PM-ER) fluids have been developed, of which the yield stress can reach more than 100 kPa and behaves a linear dependence on the electric field. A brief description on the composition and synthesizing method for the materials is given. The main merits of PM-ER fluid are as follows: high yield stress, the shear stress increasing with shear rate up to more than 103 s -1, low current density, rapid electric response and anti-sedimentation. Some perspectives on PM-ER fluid and its applications are presented.

scholarly journals Internal Damper Characteristics of Rotor System with Submerged ER Fluid Journal Bearing

1997 ◽  
Vol 3 (1) ◽  
pp. 61-71 ◽  
Author(s):  
Siyoul Jang ◽  
John A. Tichy
Keyword(s):  
Shear Stress ◽  
Electric Field ◽  
Shear Strain ◽  
Yield Stress ◽  
Electric Fields ◽  
Journal Bearing ◽  
Shear Strain Rate ◽  
Newtonian Flow ◽  
Damping Coefficients ◽  
Er Fluid

Electro-Rheological (ER) fluid behavior is similar to Bingham fluid’ s. Only when the shear stress magnitude of ER fluid exceeds the yield stress, Newtonian flow results. Continuous shear strain rate equation about shear stress which simulates Bingham-like fluid shows viscosity variations. Shear yield stress is controlled by electric fields. Electric fields in circumferential direction around the journal are also changeable because of gap distance. These values make changes of spring and damping coefficients of journal bearings compared to Newtonian flow case. Implicit viscosity variation effects according to shear strain rates of fluid are included in generalized Reynolds' equation for submerged journal bearing. Fluid film pressure and perturbation pressures are solved using switch function of Elord's algorithm for cavitation boundary condition. Spring and damping coefficients are obtained for several parameters that determine the characteristics of ER fluids under a certain electric field. From these values stability region for simple rotor-bearing system is computed. It is found that there are no big differences in load capacities with the selected electric field parameters at low eccentric region and higher electric field can support more load with stability at low eccentric region.

LANTHANUM TITANATE NANOPARTICLES ER FLUIDS WITH HIGH PERFORMANCE

2012 ◽  
Vol 26 (13) ◽  
pp. 1250079 ◽  
Author(s):  
DE WANG ◽  
RONG SHEN ◽  
SHIQIANG WEI ◽  
KUNQUAN LU
Keyword(s):  
Yield Stress ◽  
Silicone Oil ◽  
Heating Temperature ◽  
Hydroxyl Group ◽  
Lanthanum Titanate ◽  
Different Temperatures ◽  
Static Yield ◽  
Er Fluids ◽  
Er Fluid ◽  
Static Yield Stress

A new type of electrorheological (ER) fluid consisting of lanthanum titanate (LTO) nanoparticles is developed. The ER fluids were prepared by suspending LTO powder in silicone oil and the particles were fabricated by wet chemical method. This ER fluid shows excellent ER properties: The static yield stress reaches over 150 kPa under 5 kV/mm with linear dependence on the applied DC electric field, and the current density is below 10 μA/cm2. In order to investigate the affect factor on the ER behavior, the LTO powder were heated under different temperatures. The ER performances of two particles treated under different temperatures were compared and the composition changes for those particles were analyzed with TG-FTIR technique. It was found that the static yield stress of the suspensions fell from over 150 kPa to about 40 kPa and the current densities decreased prominently as the rise of the heating temperature. TG-FTIR analysis indicated that polar groups remained in the particles such as alkyl group, hydroxyl group and carbonyl group etc., contribute to the ER effect significantly. The experimental results are helpful to understand the mechanism of the high ER effect and to synthesize better ER materials.

Effect of Particle Size and Distribution on the Viscosity of a Model Electrorheological (ER) Fluid

1999 ◽  
Author(s):  
Ying Chen ◽  
Hans Conrad
Keyword(s):  
Particle Size ◽  
Reasonable Agreement ◽  
Volume Fraction ◽  
Silicone Oil ◽  
Zero Field ◽  
Effect Of Particle Size ◽  
Er Fluids ◽  
Er Fluid ◽  
Modified Equation ◽  
Single Size

Abstract The zero-field viscosity of model ER fluids consisting of glass beads in silicone oil was determined as a function of average particles size (D¯ = 3–75 μm), volume fraction (ϕ = 0.1–0.3) and bimodal mixtures of two sizes. The viscosity increased with ϕ and decreased with D¯. The viscosity of the suspensions ηs in all cases was described reasonably well by the following relation:ηs=ηs,o(ϕ)+b(ϕ)D¯2/D¯3 where ηs,o(ϕ) and b(ϕ) are constants which increase with ϕ. Reasonable agreement with the Mooney crowding equation occurred for the single size particles, giving for the crowding factor k = 1.3 + 1.5/D¯. For ϕ < 0.2 the viscosity of the bimodal mixtures could be described by a modification of the Mooney equationηsηo=exp(2.76ϕ11-k1ϕ1)exp(2.76ϕ21-k2ϕ2) where ηo is the viscosity of the silicone oil, ϕi the volume fraction of each particle size Di and ki the normal crowding factor for that size. At ϕ = 0.3 the measured values of ηs for the bimodal mixtures became appreciably larger than those calculated from the modified equation. The decrease in particle size leads to both an increase in surface area of the particles per unit volume of the suspension and to a decrease in spacing (crowding); both factors probably contributed to the increase in ηs.

THE ELECTRORHEOLOGICAL FLUIDS WITH HIGH SHEAR STRESS

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1065-1070 ◽  
Author(s):  
KUNQUAN LU ◽  
RONG SHEN ◽  
XUEZHAO WANG ◽  
GANG SUN ◽  
WEIJIA WEN
Keyword(s):  
Shear Stress ◽  
Electric Field ◽  
Yield Stress ◽  
High Performance ◽  
Electrorheological Fluids ◽  
Stress Effect ◽  
High Shear ◽  
High Shear Stress ◽  
Effective Factors ◽  
Er Fluids

A series of high performance ER fluids newly manufactured in our laboratory are presented. The yield stress of those ER fluids can reach several tens of kPa, 100 kPa and even 200 kPa, respectively. For understanding the high shear stress effect a model is proposed base on the electric field induced molecular bounding effect. The main effective factors in fabricating the high performance ER are discussed.

Polar-molecules-driven enhanced colloidal electrostatic interactions and their applications in achieving high active electrorheological materials

2008 ◽  
Vol 23 (2) ◽  
pp. 409-417 ◽  
Author(s):  
L. Xu ◽  
W.J. Tian ◽  
X.F. Wu ◽  
J.G. Cao ◽  
L.W. Zhou ◽  
...  
Keyword(s):  
Yield Stress ◽  
Electrostatic Interactions ◽  
Colloidal Particles ◽  
Sol Gel ◽  
Polar Molecules ◽  
Highly Active ◽  
Static Yield ◽  
Er Fluids ◽  
Er Fluid ◽  
Static Yield Stress

We have fabricated a class of colloidal electrorheological (ER) fluids, in which suspended TiO2 particles were synthesized by a sol-gel method and modified by 1,4-butyrolactone molecules with a permanent molecular dipole moment of 4.524 D. Compared with pure TiO2 ER fluids, the quasi-static yield stress of the polar- molecules-modified ER fluid is enhanced as high as 48.1 kPa when subjected to an external electric field of 5 kV/mm. Also, it possesses other attractive characters such as low current density (<14 μA/cm2) and low sedimentation. Based on a Green’s function method, we present a first-principles approach to investigate colloidal electrostatic interactions. Excellent agreement between experiment and theory has been shown for the enhancement ratio of quasi-static yield stress, which quantitatively reveals that enough polar molecules oriented within the field-directed gap between the colloidal particles can unexpectedly enhance the interactions, thus yielding the unusual enhancement. This shows a promising and flexible direction for achieving more highly active ER materials.

EFFECT OF RARE EARTH SUBSTITUTION ON ELECTRORHEOLOGICAL PROPERTIES OF TiO2

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2371-2377 ◽  
Author(s):  
X. P. ZHAO ◽  
J. B. YIN ◽  
L. Q. XIANG ◽  
Q. ZHAO
Keyword(s):  
Shear Stress ◽  
Rare Earth ◽  
Silicone Oil ◽  
Anatase Phase ◽  
New Class ◽  
Dc Electric Field ◽  
Er Fluids ◽  
Er Fluid ◽  
Electrorheological Properties ◽  
Rare Earth Substitution

This paper describes a new class of water-free electrorheological (ER) fluids based on nonaqueous doped TiO 2 with rare earth (RE) in silicone oil. The thermal character and crystal structure of these materials are investigated with DSC, TG and XRD. The doped TiO 2 crystals possess anatase phase and their lattice spacing varies significantly with the content of rare earth. The rheological measurements show that the doped TiO 2 ER fluid exhibits an obviously higher shear stress than that of pure TiO 2 ER fluid under dc electric field. Especially, substitution with 10mol% cerium or 8mol% lanthanum for Ti can obtain a relatively high shear stress. On the basis of dielectric and conduction measurements, we preliminarily discuss the influence of the doping of rare earth on ER effects of TiO 2.

scholarly journals Strong Electrorheological Performance of Smart Fluids Based on TiO2 Particles at Relatively Low Electric Field

2021 ◽  
Vol 8 ◽  
Author(s):  
Yuchuan Cheng ◽  
Zihui Zhao ◽  
Hui Wang ◽  
Letian Hua ◽  
Aihua Sun ◽  
...  
Keyword(s):  
Electric Field ◽  
Yield Stress ◽  
Sol Gel ◽  
Interfacial Polarization ◽  
High Yield ◽  
Characteristic Structure ◽  
High Yield Stress ◽  
Large Yield ◽  
Er Fluids ◽  
Er Fluid

Electrorheological (ER) fluids are a type of smart material with adjustable rheological properties. Generally, the high yield stress (&gt;100 kPa) requires high electric field strength (&gt;4 kV/mm). Herein, the TiO2 nanoparticles were synthesized via the sol–gel method. Interestingly, the ER fluid-based TiO2 nanoparticles give superior high yield stress of 144.0 kPa at only 2.5 kV/mm. By exploring the characteristic structure and dielectric property of TiO2 nanoparticles and ER fluid, the surface polar molecules on samples were assumed to play a crucial role for their giant electrorheological effect, while interfacial polarization was assumed to be dominated and induces large yield stress at the low electric field, which gives the advantage in low power consumption, sufficient shear stress, low leaking current, and security.

Sound Transmission Loss in Electrorheological Fluids Under DC Voltage

2000 ◽  
Author(s):  
Marek L. Szary ◽  
Maciej Noras
Keyword(s):  
Shear Stress ◽  
Sound Pressure ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Electrorheological Fluids ◽  
Sound Transmission Loss ◽  
Dc Voltage ◽  
College Of Engineering ◽  
Er Fluids ◽  
Er Fluid

Abstract Extensive investigations of sound transmission loss (STL) in electrorheological (ER) fluids were conducted in the Acoustics Laboratory in the College of Engineering, Southern Illinois University Carbondale. The STL was investigated for different kinds of ER suspensions in frequency ranges from 100 Hz to 2kHz. Applied DC voltage to the different electrodes allowed normal and shear stress to develop in the ER fluid respectively. The electric field density was variable. Sound transmission loss was obtained by measurement of the sound pressure level in front of and behind the sample. Under both normal and shear stress in ER fluid, STL decreases with increasing stress. Those properties of ER fluids can be useful in noise and vibration control applications.

TOWARDS UNDERSTANDING ER FLUIDS USING SALS/RHEOMETRY

1996 ◽  
Vol 10 (23n24) ◽  
pp. 3029-3036
Author(s):  
Bryan J. Crosby ◽  
Tom McLeish ◽  
Harry Block
Keyword(s):  
Yield Stress ◽  
Indium Tin Oxide ◽  
Volume Fraction ◽  
Ethylene Vinyl Acetate ◽  
High Volume ◽  
Polystyrene Solution ◽  
Static Yield ◽  
Poly Ethylene ◽  
Er Fluids ◽  
Er Fluid

This paper details work in Cranfield and Leeds Universities of making a stock of transparent ER fluids, which could later be utilised in a new optical electro rheometer (OER) to be assembled at Leeds University. Two basic routes were attempted. One was to use glass microspheres and the other was to use polymer spheres. In order to increase the strength of the ER effect, it was necessary to increase the volume loading while still maintaining sufficient transmission (about 75% over 2 mm). It was found to be possible to increase the ER effect quite substantially in some instances, and in others it was possible to get a near perfect refractive index match. It was not possible to combine both requirements in one fluid such that a high static yield stress was apparent in a transparent ER fluid. However one fluid was made which gave acceptable diffraction losses at high volume fractions, remained in suspension for extended periods and provide about 700 Pa yield stress at 4kV/mm and about 30% volume fraction viz: untreated poly(ethylene vinyl acetate) microspheres in Cereclor/bromonaphthalene/polystyrene solution. The OER being assembled at Leeds University is intended to record small angle light scattering (SALS) profiles, electrical and mechanical properties of ER fluids simultaneously. The OER is based around a DSR 500 machine purchased from Rheometric Scientific with quartz tools coated with transparent indium tin oxide(ITO), which is capable of measuring both steady state (DC) and oscillatory (AC) material parameters.

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