Rheological Properties Of Electrorheological Fluids Research Articles

Influences of electric field strength on rheological properties of electrorheological fluid based on hollow poly (O-phenylenediamine co O-toluidine) dispersed on silicone oil

In this study, hollow poly (O-phenylenediamine-co-O-toluidine) (POPD-co-OT) was synthesized via oxidative polymerization reaction. The POPD-co-OT was decorated into polystyrene surface core spherical particles before removing the core to obtain the hollow particles. The chemical structure and morphology of the conducting POPD-co-OT were studied with FTIR spectroscopy, proton NMR, scanning electron microscopy, and TEM. The hollow particles were applied in the dispersion phase for the preparation of electrorheological fluid (ERF). The rheological properties were investigated with a rotational rheometer, whereas the chain formation inside the ERF was observed using OM. The experimental results indicated that the shear stress of ERF increased with increasing strength of the electric field and quickly responded by impacting the external electric field strength. The ERF system is quite stable for a long time up to 200 h.

Effect of the filler composition on the electrorheological response of dielectric suspensions in an enlarged temperature range

In this article, we present the results of creation of fillers for electrosensitive rheological fluids, the rheological characteristics of which depend only on the electric field strength and are independent of the change in temperature. The material of the electrorheological fluid filler, nanosized titanium dioxide modified by aluminum cation, was synthesized by the sol-gel method. The rheological properties of electrorheological fluids on the base of synthetic MOBIL oil with TiO2 particles alloyed with 7, 9, and 12 mol% of Al were investigated in the electric field strength varying from 0 to 3.5 kV/mm. The shear stress ( τ > τ0) of electrorheological fluids was determined by a Physica MCR-301 rheometer. The highest shear stress at T = 20°C was reached in electrorheological fluid with TiO2 particles alloyed with 12 mol% of Al. Comparison of shear stress for electrorheological fluids with TiO2 particles (12 mol% Al) annealed at Tan = 600°C, 700°C, and 800°C shows that the highest result was obtained for electrorheological fluid-3 ( Tan = 700°C). The most stable values of shear stress in the temperature range from 5°C to 80°C were obtained for electrorheological fluid with TiO2 particles alloyed with 12 mol% Al annealed at Tan = 800°C.

Rheological models of mechanical behavior of electrorheological fluids under different electric field strength

To describe the results of studies of the rheological properties of electrorheological fluids in the continuous shear flow mode under step change of the electric field strength, the mechanical model based on the parallel connection of Shvedov–Bingham and Maxwell models is proposed. In the creep mode under constant electric field, the rheological behavior of electrorheological fluids is described by the standard Burgers model including serially connected viscoelastic Maxwell and Kelvin–Voigt elements.

Elastoviscoplastic behavior model of electrorheological fluids in various deformation modes

The results of investigations of rheological properties of electrorheological fluids in various deformation modes: oscillatory, continuous flow, constant applied loading – are presented in the article. A generalized rheological model on the basis of a consecutive combination of viscoplastic, elastic and two viscoelastic elements with differing relaxation times, taking into account time dependence of retarded elastic deformation, is suggested.

Influence of temperature on the electrorheological response of dielectric suspensions based on a water-containing filler

A study is made of the influence of temperature on the rheological properties of electrorheological fluids containing hydrated alumina in the form of pseudoboemite. It is shown experimentally that such electrorheological fluids possess thermal stability, preserving high indices of electrorheological activity (ER activity) up to 120°C. The use of pseudoboemite as a filler of electrorheological fluids will make it possible to ensure efficient operation of electrically controlled hydraulic devices with an extended temperature range of application.

Measuring the response time and static rheological properties of electrorheological fluids with regard to the design of valves and their controllers

The rheological properties of the commercially used electrorheological fluid Rheoil 3.0 is measured using flow channels, that provide similar flow conditions to many electrorheological applications. The static dependence of the apparent viscosity on the field strength, the shear rate and the temperature as well as the response time of a change in the viscosity upon a changed electric field are measured and approximated by a mathematical model that can be used to design electrorheological valves and to estimate their dynamic performance.

RHEOLOGICAL PROPERTIES OF ER-FLUIDS IN TERM OF MULTIPARTICLE PHYSICAL MODEL AND MONTE-CARLO COMPUTER SIMULATION

An electrorheological fluids (ERF) are the suspensions consisting of dielectric rigid particles in the viscous (or viscoelastic) media. Based on the three-dimensional well-ordered multi-particle model (the crystal model) we describe rheological properties of ERF. We use the model of cubic body-centered lattice. We also assume that the electric field is orthogonal to the velocity of shear of fluid's layers. The displacement gradients are assumed to be different (from small to finite values). For small deformations in the framework of the approach proposed and under assumptions made it was stated that the ERF can be treated as a viscoelastic body and it is consequently described on the basis of the linear theory of viscoelasticity. We obtain a complex dynamic shear modulus as a function of the electric field strength, volume fraction of filler, electric properties of components of ERF and viscosity of the fluid phase. For finite deformation the relation between stresses and shear rate gradients has also been made. The relation does not keeps whatever phenomenological or arbitrary parameters and takes into account contribution an electrostatic interaction painted by external field dipoles. From other side a bunch of computational experiments by Monte-Carlo approximation to model both the structure and the peculiarities of ERF were made. We use a procedure by Metropolis for canonic NVT ensemble and parallel computational technologies. The structural characteristics, density, energetic parameter and others for system under consideration have been estimated. In order to verify a theoretical predictions we compare both approaches and some experimental data.

SYNTHESIS AND VISCOELASTIC BEHAVIORS OF POLY(ANILINE-CO-O-ETHOXYANILINE) PARTICLES SUSPENDED ELECTRORHEOLOGICAL FLUID

Copolyanilines are synthesized by a chemical oxidation of aniline and o-ethoxyaniline with various molar ratios in an acidic media, and then characteristics of these polymers such as chemical structure, particle size and the particle size distribution were examined by using FT-IR, SEM and particle size analyzer, respectively. Suspensions of copolyaniline containing ethoxy group, namely poly(aniline-co-o-ethoxyaniline), in silicone oil have been investigated as one of many potential candidates for dry-base electrorheological (ER) fluid systems. Rotational rheometer (Physica) equipped with a high voltage generator was used to characterize the rheological properties of ER fluids from both steady shear and dynamic tests. From the steady shear experiment, we obtained flow properties and found that ER fluids exhibited the yield phenomenon. On the other hand, viscoelastic property was also obtained from the dynamic experiment. Since viscoelastic properties for ER fluids are mainly dominated by the particle chain structure, the state at different time scale was analyzed from the rheological parameters such as storage modulus (G'), loss modulus (G'') and tan δ. We conducted a strain amplitude sweep at 1 Hz under an applied electric field to determine a linear viscoelastic region first. The G' and G'' were then measured by a frequency sweep from 0.1 to 100 Hz in the linear viscoelastic region.

Electrorheological properties of poly(aniline‐co‐o‐ethoxyaniline) suspensions

AbstractSuspensions of copolyaniline containing ethoxy group, namely poly(aniline‐co‐o‐ethoxyaniline), in silicone oil have been investigated as one of many potential candidates for dry‐base electrorheological (ER) fluid systems. The copolyanilines were synthesized by a chemical oxidation of aniline and o‐ethoxyaniline with various molar ratios in an acidic media, and the characteristics of these polymers were examined by using several techniques. By using FT‐IR, SEM, and a particle size analyzer, we studied chemical structure, particle size, and the particle size distribution of the copolymer, respectively. A Physica rheometer equipped with a high voltage generator was also adopted to measure the rheological properties of ER fluids using the copolyaniline. Controlled shear stress mode was used for the shear rate sweep measurement, and the copolyaniline synthesized in this study was found to give a typical ER behavior, that is, shear stresses increase with increasing electric fields and volume fractions.

Enhanced electrorheological fluids using anisotropic particles

The electrorheological (ER) phenomenon is widely attributed to the chaining of micron-sized polarizable particles when subjected to an external electric field. It has been hypothesized that the strength of the particle–particle interactions determines the rheological properties of ER fluids. On the basis of an electrostatic polarization model, we proposed that by controlling the geometry of the particles, the dielectric properties of ER fluid can be enhanced, resulting in increased strength of the particle–particle interactions. In this work, we have developed systems featuring anisotropic particles and conducted a systematic study of the role of particle geometry in the response of ER fluids. Our findings appear to be in agreement with the electrostatic polarization model.

Electrorheological properties of poly(acene quinone) radical suspensions

As one of many potential electrorheological (ER) materials, poly(acene quinone) radicals (PAQR) were investigated. PAQRs were synthesized and the characteristics of these polymers were examined by using Fourier transform infrared, thermogravimetric analysis and pycnometer techniques. ER fluids were prepared by dispersing PAQRs in silicone oil at concentrations of 5, 15 and 25 vol%. A Physica rheometer equipped with a high-voltage generator was used to measure the rheological properties of ER fluids. Controlled shear rate and shear stress modes were used for the shear rate sweep measurement in various test conditions. Shear stresses, from the shear rate sweep experiment, increase with increasing electric fields, and poly(naphthalene quinone) radical (PNQR) ER system shows the highest yield stress among the PAQRs. In the low shear rate regime, shear stress is reduced with shear rate after the maximum point, until a critical shear rate is reached, and then ER fluid behaves as a Newtonian fluid. © 1997 John Wiley & Sons, Ltd.

Hydrodynamic Behavior of Electrorheological Fluids.

Up to now there has not been any universally accepted model that describes the basic char acteristics of electrorheological (ER) fluid. In order to find a model applicable to the prediction of rheological properties of ER fluids, experimental studies of laminar channel flow are performed for two types of ER fluids. The experimental setup is designed to provide reasonable estimates of ER fluid response to steady electric fields. Obtained data are adequately modeled using a well-established constitutive equation of Bingham plastic fluids, which is thought to be one of the most likely candidates for predicting the behavior of ER fluids. Calculations of frictional factors as functions of the proposed apparent Reynolds number are also found to be possible using the measured data. In the experiment, both the apparent viscosity and the yield stress are found to be highly dependent on electric field intensities. In addition, the analysis presented in this study predicts, with high accuracy, the dependence of the stress response in steady shear flows on electric field intensities.

Correlation between Electrical and Rheological Properties of Electrorheological Fluids

We present results of simultaneous measurements of shear stress and current flowing through a cellulose/mineral oil suspension subjected to shear and DC electric field. Single curves for the variation of apparent viscosity and normalised current are obtained when taking a simplified Mason number as variable. The different regimes observed are discussed in terms of the degree of structuration of the suspension reflected by the Mason number.

Computer simulation of structures and rheological properties of electrorheological fluids.

The structural phase diagram of electrorheological (ER) fluids as a function of dimensionless parameters lambda (the ratio of the dipolar force to the Brownian force) and Pe (the ratio of the shear force to the Brownian force) is constructed. In the phase diagram, there exist three single phases: a layerlike or chainlike crystalline phase (C), a shear-string phase (S), and a liquid phase (L). Between these single phases two phase coexistence zones of C+S and CS-L are located. The transitions between the phases are driven by the competition between the dipolar, shear, and Brownian forces. In the different phase zones,the viscosity of the ER fluid has different dependencies on Pe and h. The observed structures and corresponding rheological properties are discussed.