The Materials Science of Field-Responsive Fluids

MRS Bulletin ◽  
1998 ◽  
Vol 23 (8) ◽  
pp. 19-22 ◽  
Author(s):  
Pradeep P. Phulé ◽  
John M. Ginder
Keyword(s):  
Magnetic Field ◽  
Yield Stress ◽  
Smart Materials ◽  
Liquid Crystalline ◽  
Materials Science ◽  
Strong Field ◽  
Responsive Materials ◽  
Dielectric Particles ◽  
Mr Fluids ◽  
Er Fluids

Scientists and engineers are most familiar with single-crystal or polycrystalline field-responsive or “smart” materials with responses typically occurring while the materials remain in the solid state. This issue of MRS Bulletin focuses on another class of field-responsive materials that exhibits a rapid, reversible, and tunable transition from a liquidlike, free-flowing state to a solidlike state upon the application of an external field. These materials demonstrate dramatic changes in their rheological behavior in response to an externally applied electric or magnetic field and are known as electrorheological (ER) fluids or magnetorheological (MR) fluids, respectively. They are often described as Bingham plastics, and exhibit a strong field-dependent shear modulus and a yield stress that must be overcome to initiate gross material deformation or flow. Prototypical ER fluids consist of linear dielectric particles (such as silica, titania, and zeolites) dispersed in nonconductive liquids such as silicone oils. Homogeneous liquid-crystalline (LC) polymerbased ER fluids have also been recently reported. MR fluids are based on ferromagnetic or ferrimagnetic, magnetically nonlinear particles (e.g., iron, nickel, cobalt, and ceramic ferrites) dispersed in organic or “aqueous liquids. Unlike ER and MR fluids, ferrofluids (or magnetic fluids), which are stable dispersions of nanosized superparamagnetic particulates (~5–10 nm) of such materials as iron oxide, do not develop a yield stress on application of a magnetic field. Applications of ferrofluids are primarily in the area of sealing devices (see Rosensweig for more information). Since ferrofluids are well-known and have been extensively discussed elsewhere in the literature, they will not be treated in detail here.

MAGNETORHEOLOGICAL FLUIDS AND THEIR PROPERTIES

2005 ◽  
Vol 19 (01n03) ◽  
pp. 593-596 ◽  
Author(s):  
J. M. HE ◽  
J. HUANG
Keyword(s):  
Magnetic Field ◽  
Yield Strength ◽  
Rheological Properties ◽  
Yield Stress ◽  
Applied Magnetic Field ◽  
Magnetorheological Fluids ◽  
Mr Fluid ◽  
Variable Yield ◽  
Mr Fluids

Magnetorheological (MR) fluids are materials that respond to an applied magnetic field with a change in their rheological properties. Upon application of a magnetic field, MR fluids have a variable yield strength. Altering the strength of the applied magnetic field will control the yield stress of these fluids. In this paper, the method for measuring the yield stress of MR fluids is proposed. The curves between the yield stress of the MR fluid and the applied magnetic field are obtained from the experiment. The result indicates that with the increase of the applied magnetic field the yield stress of the MR fluids goes up rapidly.

HIGH VERSUS LOW FIELD VISCOMETRIC CHARACTERIZATION OF BIDISPERSE MR FLUIDS

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4922-4928 ◽  
Author(s):  
G. T. NGATU ◽  
N. M. WERELEY
Keyword(s):  
Magnetic Field ◽  
Yield Stress ◽  
High Field ◽  
Magnetic Flux Density ◽  
Flow Curves ◽  
Bingham Plastic ◽  
Low Field ◽  
Mr Fluids ◽  
Low Magnetic Field

Our bidisperse magnetorheological fluids are suspensions of micron (2-10μm) and nanometer (~40nm) scale magnetic iron particles in silicone or hydraulic oil. Earlier studies were conducted to determine the yield stress of these fluids at low magnetic field induction. These studies have shown the absence of saturation yield stress implying the possibility of a higher yield stress by increasing the applied field. In this study, three different bidisperse MR fluids were investigated to determine the maximum available yield stress that can be obtained at or near saturation magnetic flux density. The iron loading in the fluids varied from 50% to 80% by weight. Two types of MR cells, a low field and a high field cells, were used for the investigation. Using a parallel disc rheometer alternatively equipped with one of the two MR cells, the flow curves of the MR fluids were obtained and their yield stress determined. The yield stress of the MR fluids as a function of applied magnetic field was identified using the Bingham-Plastic constitutive model. Results show that the high field cell (maximum 1 Tesla) was able to measure shear stress up to saturation, whereas the low field cell (maximum 0.26 Tesla) could not.

EFFECT OF MAGNETIC FIELD ON PROPERTIES OF MR FLUIDS

2005 ◽  
Vol 19 (01n03) ◽  
pp. 597-601 ◽  
Author(s):  
J. HUANG ◽  
J. Q. ZHANG ◽  
J. N. LIU
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Theoretical Model ◽  
Yield Stress ◽  
Applied Magnetic Field ◽  
Mr Fluids ◽  
Magnetic Chain ◽  
Viscoplastic Properties

The yield stress is one of the most important parameters that characterize viscoplastic properties of magnetorheological (MR) fluids. Based on the microstructure of magnetic-chain a theoretical model is developed to analyze the effect of the applied magnetic field on the yield stress. It has been shown that the values of the yield stress calculated by the model agree well with the experimental data.

scholarly journals Role of Magnetorheological Fluids and Elastomers in Today’s World

2017 ◽  
Vol 11 (4) ◽  
pp. 267-274 ◽  
Author(s):  
Paweł Skalski ◽  
Klaudia Kalita
Keyword(s):  
Magnetic Field ◽  
Automotive Industry ◽  
Smart Materials ◽  
Magnetorheological Fluids ◽  
Magnetorheological Elastomer ◽  
Shock Absorbers ◽  
Damping Control ◽  
Mr Fluids ◽  
High Tension

AbstractThis paper explains the role of magnetorheological fluids and elastomers in today’s world. A review of applications of magnetorheological fluids and elastomers in devices and machines is presented. Magnetorheological fluids and elastomers belong to the smart materials family. Properties of magnetorheological fluids and elastomers can be controlled by a magnetic field. Compared with magnetorheological fluids, magnetorheological elastomers overcome the problems accompanying applications of MR fluids, such as sedimentation, sealing issues and environmental contamination. Magnetorheological fluids and elastomers, due to their ability of dampening vibrations in the presence of a controlled magnetic field, have great potential present and future applications in transport. Magnetorheological fluids are used e.g. dampers, shock absorbers, clutches and brakes. Magnetorheological dampers and magnetorheological shock absorbers are applied e.g. in damping control, in the operation of buildings and bridges, as well as in damping of high-tension wires. In the automotive industry, new solutions involving magnetorheological elastomer are increasingly patented e.g. adaptive system of energy absorption, system of magnetically dissociable [hooks/detents/grips], an vibration reduction system of the car’s drive shaft. The application of magnetorheological elastomer in the aviation structure is presented as well.

Shear and Squeeze Rheometry of Magnetorheological Fluids

2011 ◽  
Vol 305 ◽  
pp. 344-347 ◽  
Author(s):  
Hong Yun Wang ◽  
Hui Qiang Zheng
Keyword(s):  
Magnetic Field ◽  
Yield Stress ◽  
Electrical Current ◽  
Test System ◽  
Compression Stress ◽  
Shear Yield Stress ◽  
Mr Fluid ◽  
Mr Fluids ◽  
Shear Yield ◽  
The Magnetic Field

The mechanical properties of a magnetorheological (MR) fluid in shearing, compression and shearing after compression have been studied in the magnetic field which is generated by a coil carrying different magnitudes of DC electrical current on a self-constructed test system. The relations of compression stress versus compression strain, yield stress versus compression stress were studied under different magnetic fields. The compressing tests showed that the MR fluid is very stiff at small compressive strains lower than 0.13. The shear yield stress of MR fluids after compression was much stronger than that of uncompressed MR fluids under the same magnetic field. The enhanced shear yield stress of MR fluids can be utilized to design the MR clutch and brake for new structure and will make MR fluids technology attractive for many applications.

Yield and Rheological Behaviors of Magnetorheological Fluids

2010 ◽  
Vol 97-101 ◽  
pp. 875-879
Author(s):  
Jian Min He ◽  
Jin Huang ◽  
Cheng Liu
Keyword(s):  
Magnetic Field ◽  
Yield Stress ◽  
Applied Magnetic Field ◽  
Applied Field ◽  
Shear Strain Rate ◽  
Bingham Model ◽  
Bingham Plastic ◽  
Rheological Behaviors ◽  
Mr Fluids ◽  
Magnetic Chain

Magnetorheological (MR) fluids are materials that respond to an applied magnetic field with the change of their yield and rheological behaviors. In this paper, the yield and rheological behaviors of MR fluids are discussed. Based on the microstructure of magnetic chain a theoretical model is developed to analyze the effect of an applied magnetic field on the yield stress of MR fluids. Bingham model is used to describe the rheological behaviors of MR fluids subject to an applied magnetic field. The results show that altering the strength of an applied field can control the yield stress of MR fluids. The shear stress increases as the strength of an applied magnetic field increases, and it hardly changes with the increase of shear strain rate. MR fluids exhibit Bingham plastic model.

scholarly journals A Magnetorheological Fluid Damper for Rotor Applications

2004 ◽  
Vol 10 (3) ◽  
pp. 175-182 ◽  
Author(s):  
P. Forte ◽  
M. Paternò ◽  
E. Rustighi
Keyword(s):  
Magnetic Field ◽  
Rolling Bearing ◽  
Industrial Applications ◽  
Squeeze Film ◽  
Mr Fluids ◽  
Squeeze Film Dampers ◽  
Field Lines ◽  
Set Up ◽  
Er Fluids ◽  
The Magnetic Field

Even though we are still far from industrial applications, in the last decade there has been increasing attention directed toward the employment of electrorheological (ER) and magnetorheological (MR) fluids in active bearings and active squeeze film dampers in rotordynamics. MR fluids react to magnetic fields undergoing reversible changes in their mechanical characteristics, viscosity, and stiffness in particular. In previous literature, some applications of ER fluids in rotor squeeze film dampers can be found; however, on the contrary, little is reported on similar test rigs set up for MR dampers. In this work, the design of an MR squeeze film damper is presented and discussed. A numerical simulation has been carried out in order to evaluate the dynamic behavior of the damped rotor as a function of the magnetic field strength. The test rig is made of a slender shaft supported by two oilite bearings and an unbalanced disk. The damper is interfaced with the shaft through a rolling bearing. Electric coils generate the magnetic field whose field lines cross the MR film. Since the damping characteristics can be varied continuously by controlling the magnetic field, it is possible to have the optimum conditions for each regime of rotational speed. Preliminary tests are encouraging.

scholarly journals On the apparent yield stress in non-Brownian magnetorheological fluids

Soft Matter ◽  
2017 ◽  
Vol 13 (39) ◽  
pp. 7207-7221 ◽  
Author(s):  
Daniel Vågberg ◽  
Brian P. Tighe
Keyword(s):  
Magnetic Field ◽  
Yield Stress ◽  
Computer Simulations ◽  
Magnetorheological Fluids ◽  
Universal Behavior ◽  
Carrier Fluid ◽  
Mr Fluids

The viscosity of magnetorheological (MR) fluids can be increased dramatically by applying a magnetic field. Some MR fluids display a clear yield stress, while others do not. Using computer simulations, we rationalize this non-universal behavior in terms of the viscous interactions between particles and the carrier fluid.

Properties and Applications of Magnetorheological Fluids

1999 ◽  
Vol 604 ◽  
Author(s):  
M.R. Jolly
Keyword(s):  
Magnetic Field ◽  
Yield Stress ◽  
Applied Magnetic Field ◽  
Rheological Behavior ◽  
Applied Field ◽  
Mechanical Systems ◽  
Magnetorheological Fluids ◽  
Rapid Response ◽  
Basic Composition ◽  
Mr Fluids

AbstractMagnetorheological (MR) fluids are materials that respond to an applied magnetic field with a change in rheological behavior. Typically, this change is manifested by the development of a yield stress that monotonically increases with applied field. Interest in MR fluids derives from their ability to provide simple, quiet and rapid response interfaces between electronic controls and mechanical systems. In this paper, the basic composition and properties of example MR fluids are reviewed. Some contemporary applications of MR fluids are then discussed.

Compression Resistance of Magnetorheological Fluid

2010 ◽  
Vol 143-144 ◽  
pp. 624-628 ◽  
Author(s):  
Hong Yun Wang ◽  
Xiao Wang ◽  
Cheng Bi
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Yield Stress ◽  
Flux Density ◽  
Magnetic Flux Density ◽  
Compression Stress ◽  
Mr Fluids ◽  
Shear Yield ◽  
Compression Characteristics ◽  
Compression Resistance

The ability of magnetorheological(MR) fluids to resist compression in the direction of magnetic field was tested to investigate the quasi-static squeezing process of MR fluids. A experiment setup was designed and fabricated to test the compression characteristics. Under the different magnetic flux density, the curves of the MR fluids were studied for yield stress versus compression stress, compression stress versus compression strain. The compression resistance of MRF was then measured for the different magnetic flux density for comparison with the shear yield strength of the same magnetic field. The results showed that the compression resistance of the MRF was much stronger than its shear yield stress for the same magnetic field strength conditions. The compression resistance of MRF can be utilized to design new magnetorheological devices.

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