TRANSIENT BEHAVIOR OF THE MICROSTRUCTURE OF ELECTRORHEOLOGICAL FLUIDS IN SHEAR FLOW MODE

2001 ◽  
Vol 15 (06n07) ◽  
pp. 695-703 ◽  
Author(s):  
S. L. VIEIRA ◽  
M. NAKANO ◽  
S. HENLEY ◽  
F. E. FILISKO ◽  
L. B. POMPEO NETO ◽  
...  
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Shear Flow ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Transient Behavior ◽  
Electrorheological Fluids ◽  
Flow Mode ◽  
Er Fluid

It was reported that under the simultaneous stimulus of an electric field and shear, the particles in an ER fluid form lamellar formations in the direction of shear (adhered to one of the electrodes) which may be responsible for the ER activity more than the strength of the chains. In this way, it would be expected that the shear stress should change consistently with the morphology of the formations. In this work we studied the effect of shearing time, electric field strength and shear rate on the shear stress. We suggest that changes on shear stress with time are due to changes of the morphology of the lamellar formations.

Electrorheological Properties of Suspensions Prepared From Polythiophene Conductive Polymer

Materials ◽  
2005 ◽  
Author(s):  
Datchanee Chotpattananont ◽  
Anuvat Sirivat
Keyword(s):  
Shear Flow ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Applied Stress ◽  
Volume Fraction ◽  
Scaling Law ◽  
Oscillatory Shear ◽  
Steady Shear ◽  
Er Fluid

Electrorheological (ER) fluids are typically composed of polarizable particles dispersed in a non-conducting fluid. Upon the application of an electric field, chain-like or fibrillar aggregates of the suspended particles are oriented along the direction of the electric field, thereby inducing viscoelasticity and a drastic increase in viscosity. In our study, Poly(3-thiophene acetic acid), PTAA, has been developed for using as ER material. The rheological properties of this PTAA suspension upon the application of electric field were investigated under various deformations; oscillatory shear flow, steady shear, and creep. We found that PTAA based ER fluid exhibited viscoelastic behavior and showed the excellent responses under an applied electric field. Moreover, the ER response of this PTAA fluid was amplified with increases in electric field strength, particle concentration, and particle conductivity. Under the oscillatory shear, the dynamic moduli, G′ and G″, increased dramatically by 10 orders of magnitude, when the field strength was increased to 2 kV/mm. The suspensions exhibited a transition from fluid-like to solid-like behavior as the field strength increased. While under steady shear flow, the yield stress increased with electric field strength, E, and particle volume fraction, φ, according to a scaling law of the form, τy α Eαφγ. Furthermore, the creep curves of this ER fluid consisted of both elastic and viscous responses and this fluid exhibits partially elastic recovery after the removal of applied stress. The creep properties strongly depended on the magnitude of an applied stress.

HYDRODYNAMIC CHARACTERISTICS OF ELECTRORHEOLOGICAL FLUID IN A PARALLEL DUCT FLOW

2001 ◽  
Vol 15 (06n07) ◽  
pp. 980-987
Author(s):  
K. SHIMADA ◽  
S. KAMIYAMA
Keyword(s):  
Shear Rate ◽  
Friction Coefficient ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Apparent Viscosity ◽  
Wall Friction ◽  
Hydrodynamic Characteristics ◽  
Duct Flow ◽  
Newtonian Viscosity

An experimental investigation is conducted to clarify the hydrodynamic characteristics of ERF with elastic particles of smectite in a two-dimensional parallel duct of various widths. Experimental data on pressure difference to a volumetric flow rate in a supplying D.C. electric field are measured. These data are arranged to obtain the apparent viscosit by using the integral method of rheology. From the data of apparent viscosity, the wall friction coefficient is obtained. The increment of the apparent viscosity caused by the applying electric field is a function of shear rate as well as the electric field strength and the width of the duct. However, the wall friction coefficient is not a function of elecric field strength and the width of the parallel duct, but only of shear rate. The yield stress is a function of the width of the parallel duct as well as of electric field strength. The ratio of Non-Newtonian viscosity in the apparent viscosity is varied by the intensity of the shear rate.

Water-Activated Bacterial Cellulose-Based Electrorheological Fluids and Electromechanical Response of Artificial Muscle Based on Electrorheological Fluids and Siloxane Gel

2009 ◽  
Vol 87-88 ◽  
pp. 143-148
Author(s):  
Nai Xu ◽  
De Min Jia
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Water Content ◽  
Bacterial Cellulose ◽  
Yield Stress ◽  
Particle Concentration ◽  
Electrorheological Fluids ◽  
Water Yield ◽  
Composite Gel

Electrorheological (ER) characteristics of ER fluids (ERF) containing bacterial cellulose (BC) particles in silicone oil was investigated as a function of particle water content, DC electric field strength and particle concentration. It was found that the existence of water in BC particles strongly influenced the performance of water-activated ERF based on BC particles. Around 8.8 wt% water, yield stress reached its maximum valve of 1118 Pa after which it decreased with increasing water content. At the same water content, yield stress increased linearly with increasing in either electric field strength or particle concentration. The ERF based on BC particles was introduced into the poly (dimethylsiloxane) (PDMS) gels to prepare electric field sensitive composite gel. Electric fields were applied to these composite gels using flexible electrodes. Compressions of these gels with varying PDMS/ERF ratios were confirmed by the electrode displacement. It was found that 50/50 PDMS/ERF gel exhibited the maximum displacement of 102um at 2 kV/mm electric field.

CHARACTERISATION OF THE COMPLEX SHEAR MODULUS PROPERTIES OF ELECTRO-RHEOLOGICAL FLUIDS BY THE DIRECT STIFFNESS AND MASTER CURVE TECHNIQUES

1996 ◽  
Vol 10 (23n24) ◽  
pp. 3227-3236 ◽  
Author(s):  
S O Oyadiji
Keyword(s):  
Field Strength ◽  
Shear Modulus ◽  
Electric Field ◽  
Electric Field Strength ◽  
Loss Factor ◽  
Master Curve ◽  
Measured Temperature ◽  
Direct Stiffness ◽  
Er Fluid ◽  
Field Strengths

The direct stiffness technique was employed to characterise the complex modulus properties of a silicone oil-based electrorheological fluid over a frequency range from 30Hz to 300Hz and a temperature range from 0°C to 60ºC. The ER fluid device utilised was a set of concentric cylinders possessing a radial gap of 3mm between adjacent cylinders. Electric field strengths of between 0kV/mm and 2kV/mm were applied across the ER fluid. The results show that the shear modulus of the ER fluid decreased monotonically as the temperature was increased from 0ºC to 60ºC. Overall, the shear modulus decreased by a factor of up to 20. On the other hand, the shear loss factor increased from a low value of about 0.05 at 0ºC to a high value of about 1.0 at 60ºC. Conversely, as the electric field strength was increased from 0kV/mm to 2kV/mm, the shear modulus increased whereas the loss factor decreased. At all temperatures and electric field strengths of these investigations, both the shear modulus and loss factor increased in value as the excitation frequency was increased. The sets of measured temperature- and frequency-dependent data were converted, using the master curve technique, to master curves of shear modulus and loss factor which vary with frequency over several decades at a constant reference temperature and for varying levels of the electric field strength.

DIFFERENCES IN STEADY CHARACTERISTICS AND RESPONSE TIME OF ERF ON ROTATIONAL FLOW BETWEEN ROTATING DISK AND CONCENTRIC CYLINDER

2001 ◽  
Vol 15 (06n07) ◽  
pp. 1050-1056 ◽  
Author(s):  
K. SHIMADA ◽  
H. NISHIDA ◽  
T. FUJITA
Keyword(s):  
Shear Rate ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Current Density ◽  
Rotating Disk ◽  
Settling Time ◽  
Rotational Flow ◽  
Concentric Cylinder ◽  
Constant Shear Rate

We made an experimental investigation of the steady characteristics of torque, current density, and response time of ERF on rotational flow of the disk and the concentric cylinder. We used smectite particles suspension ERF and D.C. electric field. We compared the steady shearstress, current density, and the rise and settling time of the concentric cylinder and with those of the rotating disk. Then we clarified the differences. At a larger electric field strength, the shear stress, yield stress, and apparent viscosity to a constant shear rate in the case of the rotating disk are larger than they are in the case of the rotating concentric cylinder. However, at a larger electric field strength, the current density to a constant shear rate in the case of the rotating disk is smaller than it is in the case of the rotating concentric cylinder. Rise time of torque in the case of the rotating disk is faster than it is in the case of the rotating concentric cylinder. However, rise time of current density in the case of the rotating disk is slower than it is in the case of the rotating concentric cylinder at a small electric field strength. On the other hand, the difference of settling time of torque and current density between the rotating disk and the rotating concentric cylinder is changed by the electric field strength and shear rate. The settling time of torque in the case of the rotating disk is faster than it is in the case of the rotating concentric cylinder at a large electric field strength and large shear rate. The settling time of current density in the case of the rotating disk is slower than it is in the case of rotating concentric cylinder at a small electric field strength. Based on these results, the rotating disk has an efficiency of obtained torque to given electric power greater than that of the rotating concentric cylinder.

Droplet Deformation and Breakup due to Shear Flow and Electric Field in a Confined Geometry

2018 ◽  
Author(s):  
Rattandeep Singh ◽  
Supreet Singh Bahga ◽  
Amit Gupta
Keyword(s):  
Shear Flow ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Threshold Value ◽  
Droplet Breakup ◽  
Droplet Deformation ◽  
Spherical Droplet ◽  
Low Viscosity ◽  
Boltzmann Method

In this work, the behavior of a spherical droplet suspended in a confined shear flow and subjected to an external electric field has been investigated. The continuous and dispersed fluids are treated as leaky dielectrics. The subsequent flow has been computed numerically using a low spurious current, multi-component lattice Boltzmann method coupled with a leaky dielectric model. The numerical model has been validated by analyzing droplet deformation due to shear flow and electric field separately. The results obtained are shown to be in good agreement with earlier published analytical solutions. Droplet elongation predicted by our simulations rises with increase in the electric field strength. Beyond a threshold value of electric field, breakup of droplet into smaller droplets is observed. Droplet breakup in case of fluids with equal viscosity is observed at low electric field strength as compared to low viscosity ratio drops.

ELECTRORHEOLOGY OF DISPERSIONS OF BaxSr(1-x)TiO3 IN SILICONE OIL UNDER AC OR DC ELECTRIC FIELD

2012 ◽  
Vol 26 (14) ◽  
pp. 1250081 ◽  
Author(s):  
GLAUBER M. S. LUZ ◽  
ANTONIO J. F. BOMBARD ◽  
SILVIO L. M. BRITO ◽  
DOUGLAS GOUVÊA ◽  
SHEILA L. VIEIRA
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Electric Field ◽  
Silicone Oil ◽  
Ferroelectric Materials ◽  
Dc Electric Field ◽  
Ac Fields ◽  
Er Fluid ◽  
Constant Shear Rate

Electrorheology (ER) of ferroelectric materials such as nanometric BaTiO 3 is still not fully understood. In this paper, nanoparticles of Ba x Sr (1-x) TiO 3 (where x = 0.8, 0.9 or 1.0) were synthesized using the method of Pechini, calcinated at 950°C, and after, lixiviated under pH 1 or pH 5. A controlled stress rheometer (MCR-301) was used to make the ER characterization of dispersions made of Ba x Ti 1-x O 3 in silicone oil (30% w/w), where (a) shear stress as a function of DC electric field (under constant shear rate) or (b) shear stress as a function of shear rate (under constant AC or DC electric field) were measured. We observed that electrophoresis occurred under electric field DC, creating a concentration gradient which induced phase separation in ER fluid. On the other hand, under AC fields above 1 kV/mm, the ER effect is stronger than for DC field, and almost without electrophoresis. Furthermore, there is an AC frequency, dependent on the disperse phase, where the ER effect has a maximum.

Study on the Test System of ERF's Performance

2013 ◽  
Vol 579-580 ◽  
pp. 813-817
Author(s):  
Xin Sheng He ◽  
Peng Huang ◽  
Kai Fei ◽  
Xiao Yi Zhang ◽  
Wei Zeng Chen ◽  
...  
Keyword(s):  
Shear Stress ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Apparent Viscosity ◽  
Performance Test ◽  
Performance Testing ◽  
Test System ◽  
Relationship Of ◽  
The Relationship

Electrorheological fluid (ERF) is a new kind of smart materials, which has a great deal of market value and broad application prospects. To meet the needs of the ERFs performance testing, design and produce of the ERF's performance test system are based on the relationship of the apparent viscosity, shear stress and electric field strength. Select the NDJ-8S digital viscometer, high voltage DC power supply, liquid container, and other parts to constitute the ERFs performance test system after considering the relationship of the apparent viscosity, shear stress, shear rate and electric field strength. The system has potentials to control voltage, change velocity, change the distance between the parallel panels, and test the yield stress of the ERF, shear stress, viscosity and other parameters. The study introduces the hardware and software device, the related experiments, and obtains the relationship of the viscosity, rotational speed, voltage, and plate gap.

Properties and Structure of Ni/TiO2/Polar Molecule Core-Shell Particles Electrorheological Fluid

2012 ◽  
Vol 512-515 ◽  
pp. 2166-2170
Author(s):  
Suo Kui Tan ◽  
Xiao Ping Song ◽  
Hong Zhao ◽  
Song Ji ◽  
Li Qiao ◽  
...  
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electrorheological Fluid ◽  
Polar Molecule ◽  
Fluid Properties ◽  
Structure Observation ◽  
Shell Particles ◽  
The Relationship ◽  
Er Fluid

By means of mechanical properties test and structure observation， the relationship among electric field strength, polar molecule type, content on the Ni/TiO2group electrorheological fluid properties have been analyzed. It is found that with increasing electric field strength，the properties of electrorheological fluid increased for same composition ER fluid. Different type polar molecules have distinct effect. For same particle，with increasing polar molecule content，the property is increased, but there is a critical value . Polar molecule make particles chain of electrorheological fluid become strong，coarse and interweaved each other.

Modeling and Analysis of the Electrorheological Fluids (Suspension Flow) with Aligned-Structure Reformation

2012 ◽  
Vol 77 ◽  
pp. 103-107
Author(s):  
Young Wook Seo ◽  
Hyoung Jin Choi ◽  
Yong Sok Seo
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Shear Rate ◽  
Field Strength ◽  
Electrorheological Fluids ◽  
Suspension Flow ◽  
Polarization Model ◽  
Modeling And Analysis ◽  
Proposed Model ◽  
Er Fluids

A new rheological model is applied to the analysis of the behavior of electrorheological (ER) fluids. A comparison of the model’s predictions with experimental data shows that the proposed model correctly predicts the shear stress behavior both quantitatively and qualitatively. The shear stress data for the aligned particles’ structure reformation can be fitted as a function of shear rate with the new model. The yield stress was found to be almost linearly dependent on the field strength, different from the predictions of the polarization model.

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