Dynamic Fatigue Characteristics of Electrorheological Fluids: Experimental Results

2006 ◽  
Vol 324-325 ◽  
pp. 177-180 ◽  
Author(s):  
Seung Bok Choi ◽  
Kum Gil Sung
Keyword(s):  
Yield Stress ◽  
Electrorheological Fluids ◽  
Flow Mode ◽  
Electric Voltage ◽  
Operating Cycle ◽  
Field Dependent ◽  
Flow Motion ◽  
Fatigue Characteristics ◽  
Er Fluid ◽  
Dynamic Fatigue

In this study, the dynamic fatigue characteristics of chemical starch-based ER fluid are experimentally investigated. A flow mode type apparatus is manufactured to activate the flow motion of the ER fluid. After evaluating the field-dependent Bingham property, three important dynamic fatigue characteristics; yield stress, current density and response time of the ER fluid are investigated as a function of the operating cycle. The dynamic operation for the flow motions is undertaken up to one million cycles and electric voltage is applied to the electrodes. In addition, the change of the particles of the ER fluid is microscopically observed to advocate the variation of the yield stress.

BINGHAM AND RESPONSE CHARACTERISTICS OF ER FLUIDS IN SHEAR AND FLOW MODES

2001 ◽  
Vol 15 (06n07) ◽  
pp. 1017-1024 ◽  
Author(s):  
H. G. LEE ◽  
S. B. CHOI ◽  
S. S. HAN ◽  
J. H. KIM ◽  
M. S. SUH
Keyword(s):  
Electric Fields ◽  
Flow Mode ◽  
Shear Mode ◽  
Damping Force ◽  
Response Characteristics ◽  
Operating Modes ◽  
Field Dependent ◽  
Different Temperatures ◽  
Er Damper ◽  
Er Fluid

This paper presents field-dependent Bingham and response characteristics of ER fluid under shear and flow modes. Two different types of electroviscometers are designed and manufactured for the shear mode and flow mode, respectively. An ER fluid consisting of soluble chemical starches (particles) and silicon oil is made and its field-dependent yield stress is experimentally distilled at two different temperatures using the electroviscometers. Time responses of the ER fluid to step electric fields are also evaluated under two operating modes. In addition, a cylindrical ER damper, which is operated under the flow mode, is adopted and its measured damping force is compared with predicted one obtained from Bingham model of the shear and flow mode, respectively.

Temperature Effect on Yield Stress of Electrorheological Fluids: Experimental Investigation

2006 ◽  
Vol 324-325 ◽  
pp. 173-176 ◽  
Author(s):  
Seung Bok Choi ◽  
Jung Woo Sohn ◽  
Y.S. Lee
Keyword(s):  
Temperature Effect ◽  
Yield Stress ◽  
Electrorheological Fluids ◽  
Shear Mode ◽  
Liquid Particle ◽  
Carrier Liquid ◽  
Field Dependent ◽  
Effect On Yield ◽  
Er Fluids ◽  
Rotational Shear

In the present paper, temperature effect on yield stress of electrorheological fluids is experimentally investigated. A rotational shear-mode type electroviscometer is designed and manufactured for the identification of Bingham characteristics of ER fluids. Optimization of ER fluids is undertaken with carrier liquid, particle and additive treatment and then four different ER fluids are prepared for the test. The field-dependent yield stress, current density and response time of optimized ER fluids are compared at various temperature conditions.

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.

Nondimensional Analysis of Electrorheological and Magnetorheological Dampers Using a Herschel-Bulkley Constitutive Model

Aerospace ◽  
2003 ◽  
Author(s):  
Norman M. Wereley
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Constitutive Model ◽  
Yield Stress ◽  
Flow Mode ◽  
Damping Capacity ◽  
Bingham Plastic ◽  
Field Dependent ◽  
Local Shear ◽  
Local Shear Stress

Quasisteady modeling of linear stroke flow mode magnetorheological (MR) and electrorheological (ER) dampers has focused primarily on the utilization of the Bingham-plastic constitutive model to assess performance metrics such as damping capacity. In such Bingham-plastic MR (or ER) flows, the yield stress of the fluid, τy, is activated by applying magnetic (or electric) field. The Bingham-plastic model assumes that the material is in either (1) a preyield condition where the local shear stress is less than the yield stress, τ < τy, or (2) a postyield condition, where the local shear stress is greater than the yield stress, τ > τy, so that the material flows with a constant postyield viscosity. The objective of this paper is to analyze the damping capacity of such a controllable MR or ER damper in the situation when the field dependent fluid exhibits postyield shear thinning or thickening behavior, that is, the postyield viscosity is a function of shear rate. A Herschel-Bulkley model with a field dependent yield stress is proposed, and the impact of shear rate dependent viscosity on damping capacity is assessed. Key analysis results—velocity profile, shear stress profile, and damping coefficient—are presented in a nondimensional formulation that is consistent with prior results for the Bingham-plastic analysis. The nondimensional analysis formulated here clearly establishes the Bingham number as the independent variable for assessing flow mode damper performance.

PRACTICE-RELEVANT ASPECTS OF CONSTRUCTING ER FLUID ACTUATORS

1996 ◽  
Vol 10 (23n24) ◽  
pp. 3243-3255 ◽  
Author(s):  
H. Janocha ◽  
B. Rech ◽  
R. Bölter
Keyword(s):  
Electric Fields ◽  
Electrorheological Fluids ◽  
Flow Mode ◽  
Process Automation ◽  
Rotational Viscometer ◽  
Energy Transducer ◽  
The Individual ◽  
Er Fluids ◽  
The University ◽  
Er Fluid

The flow resistance of electrorheological fluids (ER fluids) can be controlled by applying electric fields. Thus, ER fluids are suitable for the application in actuators, using high-voltage sources for the generation of the field. The behaviour of an ER fluid actuator not only depends on the properties of the individual actuator components (ER fluid, energy transducer and energy source) but especially on their combined efforts as a system. Based on a possible scheme for the design of ER fluid actuators, this paper presents important practice-relevant aspects of a systematic actuator construction. Here the behaviour of a commercial ER suspension is examined and compared to a homogeneous ER fluid without yield point using a rotational viscometer and a flow-mode damper realized at the Laboratory of Process Automation (LPA) of the University of Saarland.

Fatigue Properties of Smart Electrorheological Materials

2005 ◽  
Vol 297-300 ◽  
pp. 1172-1177
Author(s):  
Seung Bok Choi ◽  
Kyung Su Kim
Keyword(s):  
Yield Stress ◽  
Current Density ◽  
Fatigue Property ◽  
Fatigue Properties ◽  
Property A ◽  
Electrode Gap ◽  
Operating Cycle ◽  
Hydraulic Unit ◽  
Mechanical Fatigue ◽  
Field Dependent

In this study, both mechanical and electrical fatigue properties of electrorheological (ER) materials whose global characteristics can be controlled by an external electric field are experimentally evaluated. In order to investigate the mechanical fatigue property, a linear reciprocating apparatus is devised and operated by the hydraulic unit. Two important characteristics of methylcellulose based ER material: the field-dependent yield stress and current density are investigated as a function of the operating cycle. The electrical fatigue property is investigated by applying high voltage to the ER material domain through the electrode gap. The voltage is imposed in on-off manner for the specific cycles by changing the field intensity. The yield stress and current density of the ER material are evaluated at each specified cycle and surface roughness of the electrode is observed as well.

Nondimensional Analysis of Electrorheological and Magnetorheological Dampers Using a Herschel-Bulkley Constitutive Model

2003 ◽  
Author(s):  
Norman M. Wereley
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Constitutive Model ◽  
Yield Stress ◽  
Flow Mode ◽  
Damping Capacity ◽  
Bingham Plastic ◽  
Field Dependent ◽  
Local Shear ◽  
Local Shear Stress

Quasisteady modeling of linear stroke flow mode magnetorheological (MR) and electrorheological (ER) dampers has focused primarily on the utilization of the Bingham-plastic constitutive model to assess performance metrics such as damping capacity. In such Bingham-plastic MR (or ER) flows, the yield stress of the fluid, τy, is activated by applying magnetic (or electric) field. The Bingham-plastic model assumes that the material is in either (1) a preyield condition where the local shear stress is less than the yield stress, τ < τy, or (2) a postyield condition, where the local shear stress is greater than the yield stress, τ > τy, so that the material flows with a constant postyield viscosity. The objective of this paper is to analyze the damping capacity of such a controllable MR or ER damper in the situation when the field dependent fluid exhibits postyield shear thinning or thickening behavior, that is, the postyield viscosity is a function of shear rate. A Herschel-Bulkley model with a field dependent yield stress is proposed, and the impact of shear rate dependent viscosity on damping capacity is assessed. Key analysis results — velocity profile, shear stress profile, and damping coefficient — are presented in a nondimensional formulation that is consistent with prior results for the Bingham-plastic analysis. The nondimensional analysis formulated here clearly establishes the Bingham number as the independent variable for assessing flow mode damper performance.

Coating of Polyaniline with an Insulating Polymer to Improve the Power Efficiency of Electrorheological Fluids

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1931-1939 ◽  
Author(s):  
J. Akhavan ◽  
K. Slack ◽  
V. Wise ◽  
H. Block
Keyword(s):  
Power Efficiency ◽  
Electrorheological Fluids ◽  
Emeraldine Base ◽  
Heavy Duty ◽  
Base Form ◽  
Static Yield ◽  
High Fields ◽  
Er Fluids ◽  
Er Fluid ◽  
A Current

Currents drawn under high fields often present practical limitations to electrorheological (ER) fluids usefulness. For heavy-duty applications where large torques have to be transmitted, the power consumption of a ER fluid can be considerable, and for such uses a current density of ~100μ A cm -2 is often taken as a practical upper limit. This investigation was conducted into designing a fluid which has little extraneous conductance and therefore would demand less current. Selected semi-conducting polymers provide effective substrates for ER fluids. Such polymers are soft insoluble powdery materials with densities similar to dispersing agents used in ER formulations. Polyaniline is a semi-conducting polymer and can be used as an effective ER substrate in its emeraldine base form. In order to provide an effective ER fluid which requires less current polyaniline was coated with an insulating polymer. The conditions for coating was established for lauryl and methyl methacrylate. Results from static yield measurements indicate that ER fluids containing coated polyaniline required less current than uncoated polyaniline i.e. 0.5μ A cm -2. The generic type of coating was also found to be important.

Magnetic field dependent steady-state shear response of Fe3O4 micro-octahedron based magnetorheological fluids

2018 ◽  
Vol 20 (30) ◽  
pp. 20247-20256 ◽  
Author(s):  
A. V. Anupama ◽  
V. B. Khopkar ◽  
V. Kumaran ◽  
B. Sahoo
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Yield Stress ◽  
Applied Magnetic Field ◽  
Rheological Behaviour ◽  
Magnetorheological Fluids ◽  
Shear Response ◽  
Field Dependent ◽  
Dynamic Yield ◽  
Magneto Rheological

The magneto-rheological behaviour of fluids containing soft-ferrimagnetic Fe3O4 micro-octahedrons (M = magnetization, τY = dynamic yield-stress and H = applied-magnetic-field).

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