MOLECULAR ORIENTATION AND ELECTROHYDRODYNAMIC FLOW IN HOMOGENEOUS ER FLUIDS

2001 ◽  
Vol 15 (06n07) ◽  
pp. 973-979 ◽  
Author(s):  
HIROKI IWATSUKI ◽  
NAOTO GOHKO ◽  
HIROSHI KIMURA ◽  
YUICHI MASUBUCHI ◽  
JUN-ICHI TAKIMOTO ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Electric Field ◽  
Molecular Orientation ◽  
Liquid Crystalline ◽  
Polypropylene Glycol ◽  
Homogeneous Fluid ◽  
Immiscible Liquids ◽  
Electrohydrodynamic Flow ◽  
Er Fluids ◽  
Er Fluid

Homogeneous ER fluid is an ER fluid which consists of a homogeneous fluid only; it is neither a suspension nor a blend of immiscible liquids. Various liquid crystals are typical examples of homogeneous ER fluids. Recently, we have found that urethane-modified polypropylene glycol (UPPG) is one of the very few examples of homogeneous ER fluids which show no liquid crystalline order. In order to clarify the mechanism of the ER effect in this fluid, we have studied, in this paper, electrohydrodynamic flow under shear and electric field.

THE FREQUENCY DEPENDENCE AND NON-LINEAR DIELECTRIC PROPERTY OF ER FLUID

1996 ◽  
Vol 10 (23n24) ◽  
pp. 3073-3080 ◽  
Author(s):  
KUNQUAN LU ◽  
WEIJIA WEN ◽  
CHENXI LI
Keyword(s):  
Dielectric Property ◽  
Field Strength ◽  
Electric Field ◽  
Frequency Dependence ◽  
Threshold Value ◽  
Shear Stresses ◽  
Linear Behavior ◽  
Non Linear ◽  
Er Fluids ◽  
Er Fluid

The frequency dependence of the shear stress in ac field and the non-linear dielectric property of ER fluid have been studied. We find that the shear stresses of some water-free ER fluids increase monotonously with the frequency and tend to reach saturated values at high frequency. The measurements on KNbO 3/silicone ER fluid show that the shear stresses under 103 Hz frequency a.c. field are several times or even an order larger than that under d.c. field for the same field strength. The studies of non-linear dielectric properties of ER fluids show that the permittivity of ER fluid increases linearly with increasing field strength when the electric field exceeds a threshold value E 1 and tends to a saturated constant beyond a high field strength E 2. Correspondingly the current density follows linear behavior no longer in the region between E 1 and E 2. A model based on the rearrangement of the particles under the electric field. which causes the variation of the dielectric property of the ER fluid, is proposed and the analysis is consistent with the measured results.

ELECTRIC-FIELD-INDUCED PHASE SEPARATION IN ELECTRORHEOLOGICAL FLUIDS

1994 ◽  
Vol 08 (20n21) ◽  
pp. 2811-2822 ◽  
Author(s):  
XIN-LU TANG ◽  
KE-QIN ZHU ◽  
E. GUAN ◽  
XIAO-PING WU
Keyword(s):  
Phase Separation ◽  
Electric Field ◽  
Strong Electric Field ◽  
Processing System ◽  
Video Camera ◽  
Two Dimensional ◽  
Critical Fields ◽  
Computer Image Processing ◽  
Er Fluids ◽  
Er Fluid

The phase separation into a high-density and a low-density phase, which occurs after a strong electric field is applied to an ER fluids, is demonstrated in terms of the Coulomb interaction energy of the system. The phase separation is manifested by two-dimensional pattern observed in the field direction by means of a pair of transparent glass (TG) electrodes. The development of phase separation with an increasing field is recorded by a computer image processing system consisting of a CCD video camera. The patterns are irregular and their characteristic sizes are determined by two-dimensional auto-correlation approach. The dependency of those patterns on external electric field is analyzed based on statistical methods. Two critical fields are presented to characterize the electric-field-induced phase separation process in the ER fluid.

PERFORMANCE ANALYSIS OF AN ENGINE MOUNT FEATURING ER FLUIDS AND PIEZOACTUATORS

1996 ◽  
Vol 10 (23n24) ◽  
pp. 3143-3157 ◽  
Author(s):  
S.H. CHOI ◽  
Y.T. CHOI ◽  
S.B. CHOI ◽  
C.C. CHEONG
Keyword(s):  
Electric Field ◽  
Frequency Domain ◽  
Control Technique ◽  
Operating Frequency ◽  
Frequency Range ◽  
Engine Mounts ◽  
Operating Frequency Range ◽  
Engine Mount ◽  
Er Fluids ◽  
Er Fluid

Conventional rubber mounts and various types of passive or semi-active hydraulic engine mounts for a passenger vehicle have their own functional aims on the limited frequency band in the broad engine operating frequency range. In order to achieve high system performance over all frequency ranges of the engine operation, a new type of engine mount featuring electro-rheological(ER) fluids and piezoactuators is proposed in this study. A mathematical model of the proposed engine mount is derived using the bond graph method which is inherently adequate to model the interconnected hydromechanical system. In the low frequency domain, the ER fluid is activated upon imposing an electric field for vibration isolation while the piezoactuator is activated in the high frequency domain. A neuro-control algorithm is utilized to determine control electric field for the ER fluid, and H∞ control technique is adopted for the piezoactuator Comparative works between the proposed and single-actuating(ER fluid only or piezoactuator only) engine mounts are undertaken by evaluating force transmissibility over a wide operating frequency range.

Effect of Urea Content on Properties and Microstructure of Ni/TiO2 Group Particles ER Fluid

2012 ◽  
Vol 496 ◽  
pp. 25-29 ◽  
Author(s):  
Suo Kui Tan ◽  
Xiao Ping Song ◽  
Hong Zhao ◽  
Song Ji ◽  
Hong Yan Guo ◽  
...  
Keyword(s):  
Electric Field ◽  
Mass Ratio ◽  
Microstructure Observation ◽  
Urea Content ◽  
Column Structure ◽  
Dc Electric Field ◽  
Er Fluids ◽  
Er Fluid

This paper emphasis have researched the effect of Ni/TiO2group particles modifier with Urea by properties and microstructure，it has showed that ER activity of the particles were closely associated with urea content. When the mass ratio of urea/Ti is 30%, The microstructure observation of the ER fluids under DC electric field showed that the particles aggregated to form thicker and dense column structure when the mass ratio of Urea/Ti is 30%, while the column structure were broken when excessive urea (>30%) was added. A thin and loose column structure was formed in non-urea added ER fluid.

A Valve-Integrated Microactuator Using Homogeneous ER Fluid

2003 ◽  
Vol 15 (2) ◽  
pp. 244-250 ◽  
Author(s):  
Kazuhiro Yoshida ◽  
◽  
Hiroshi Yano ◽  
Jung-Ho Park ◽  
Shinichi Yokota ◽  
...  
Keyword(s):  
Electric Field ◽  
Power Density ◽  
High Power ◽  
Applied Electric Field ◽  
Fluid Power ◽  
High Power Density ◽  
Viscosity Change ◽  
Micro Gripper ◽  
Er Fluids ◽  
Er Fluid

For micromachines using fluid power with high power density, a valve-integrated microactuator using homogeneous ER (electro-rheological) fluid is proposed and developed. For higher performance of the micro ER valve that controls the flow of homogeneous ER fluid using the viscosity change due to the applied electric field, the characteristics of the micro ER valve with different ER fluids are experimentally investigated. Also, a polyimide-diaphragm fluid microactuator is proposed, fabricated, and tested. Then the valve-integrated microactuator is fabricated using above devices and the characteristics are experimentally examined. A micro gripper driven by the microactuator is demonstrated.

HYDRODYNAMIC CHARACTERISTICS OF ER FLUID FLOWS IN JOURNAL BEARINGS

2003 ◽  
Vol 17 (01n02) ◽  
pp. 205-208 ◽  
Author(s):  
KE-QIN ZHU ◽  
JIE PENG
Keyword(s):  
Electric Field ◽  
Journal Bearing ◽  
Fluid Flows ◽  
Journal Bearings ◽  
Hydrodynamic Characteristics ◽  
Eccentricity Ratio ◽  
High Eccentricity ◽  
Bingham Plastic ◽  
Er Fluids ◽  
Er Fluid

A numerical analysis is performed on the hydrodynamic characteristics of electrorheological(ER) fluid flows in journal bearings based on the basic hydrodynamic equations. The flow field is assumed to be incompressible and isotropic, the Bingham plastic model is used to describe the behavior of ER fluids. The effect of bearing eccentricity ratio and applied electric field intensity has been studied attentively. It shows that control of the journal bearing through external electric field is much more feasible in high eccentricity ratio bearing than in low eccentricity ratio one.

CALCULATION OF THE HYDRODYNAMIC CHARACTERISTIC OF THE ER-FLUID IN A PLANE CHANNEL-CONDENSER FOR THE EXPONENTIAL-LAW FLUID FLOW

2001 ◽  
Vol 15 (06n07) ◽  
pp. 996-1008
Author(s):  
E. V. KOROBKO ◽  
N. I. EGOROV ◽  
A. A. MOKEEV
Keyword(s):  
Electric Field ◽  
Rectangular Cross Section ◽  
Complete Solution ◽  
Plane Channel ◽  
Hydrodynamic Characteristic ◽  
Exponential Law ◽  
Wide Range ◽  
Er Fluids ◽  
First Time ◽  
Er Fluid

A historical survey is made of the works devoted to physico-mathematical modeling of transfer processes of the ER-fluids whose peculiarities are determined by the regularities in changing the internal structure of a liquid carrier in the presence of an electric field. The difficulties encountered in the statement and complete solution of a system of the Maxwell equations and the motion equation of a fluid with complicated rheology are discussed. For the first time the hydrodynamic characteristic (flow rate, pressure drop, velocity profile) of an ER-fluid in a channel-condensor of the simplist form, i.e. with a rectangular cross-section are calculated using the most complicated phenomenological equation of state, i.e. having the exponential — law dependence of shear stress on shear rate and applied electric field intensity. The relations obtained can be employed in designing the hydrodynamic systems in a wide range of flow velocities and electric-field intensities.

Orientation in stretched polymer-dispersed liquid crystals

1998 ◽  
Vol 76 (11) ◽  
pp. 1642-1647 ◽  
Author(s):  
Julien Brazeau ◽  
Yanick Chénard ◽  
Yue Zhao
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Molecular Orientation ◽  
Liquid Crystalline ◽  
Polymer Dispersed Liquid Crystals ◽  
Polymer Dispersed ◽  
Infrared Dichroism ◽  
Semicrystalline Matrix ◽  
Macroscopic Orientation ◽  
Strain Direction

The orientation behavior of liquid crystal molecules in stretched films of polymer-dispersed liquid crystals (PDLC) was investigated by means of infrared dichroism. The liquid crystal used is 4prime-octyl-4-biphenyl-carbonitrile (8CN); the polymer matrices are semicrystalline poly(epsilon-caprolactone) (PCL) and an amorphous miscible blend of PCL with poly(vinyl chloride) (PVC). 8CN was found to have a limit of solubility below 5 wt.% in PCL. We show that an uniaxial stretching can effectively induce a macroscopic orientation of 8CN, and that this orientation can be preserved in the films after removal of the extensional force at room temperature, where 8CN is in its liquid crystalline phase. The molecular orientation is obtained even by stretching PDLC films with 8CN in the liquid state. These results suggest that an elongated polymer cavity in stretched PDLC imposes LC director fields with respect to the long axes of the droplets, which are aligned parallel to the strain direction. The experiments also reveal that the orientation of 8CN is higher in stretched PDLC with a semicrystalline matrix (PCL) than with an amorphous matrix (the PCL-PVC blend), and that the sizes of the LC droplets also have a slight effect on the induced orientation. This work represents a first step in the exploration of new electrooptical effects of PDLC through the presence of a uniform orientation of the liquid crystal molecules and modifications of the polymer cavity at the electrical field-off state.Key words: polymer-dispersed liquid crystals, molecular orientation, infrared dichroism, electrooptical materials.

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