SUBSTITUTION OF MICRON BY NANOMETER SCALE POWDERS IN MAGNETORHEOLOGICAL FLUIDS

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1374-1380 ◽  
Author(s):  
A. CHAUDHURI ◽  
G. WANG ◽  
N. M. WERELEY ◽  
VASIL TASOVKSI ◽  
R. RADHAKRISHNAN
Keyword(s):  
Yield Stress ◽  
Iron Powder ◽  
Weight Fraction ◽  
Fluid Sample ◽  
Mr Fluid ◽  
Carrier Fluid ◽  
Nano Powder ◽  
Mr Fluids ◽  
Micron Size ◽  
Size Powder

The effects of substitution of micron size powder by nanometer size powder in magnetorheological (MR) fluids are investigated in this study. Three MR fluid samples containing iron powder with 45% weight fraction in a carrier fluid were made by Materials Modification Inc. The difference among these three fluids is size of the magnetic particles. The first MR fluid sample contained only micron size iron powder with 10μm particle size. In the second sample, 5% micron iron was substituted with nano powders having 30~40nm mean diameter, while the third sample had 37.5% micron powder and 7.5% nano powder. Rheological tests were conducted on the three samples using a parallel disk rheometer. Highest yield stress was observed in the second MR fluid sample containing 40% micron and 5% nano iron powder. By replacing only 5% micron iron powder with nanoparticles, we achieved substantial increment in yield stress. However, when nano powder content is increased to 7.5%, the yield stress decreases and is lower than that in the all micron MR fluid. Thus, by doping a reasonable percent of nano iron powder in the MR fluid, a substantial change in the rheological characteristics is obtainable. Further investigations of effects of nano iron powder in MR fluids for higher weight fraction MR fluids will be carried out in future.

Nanometer and Micron Sized Particles in a Bidisperse Magnetorheological Fluid

2003 ◽  
Author(s):  
N. M. Wereley ◽  
J. Trihan ◽  
S. Kotha ◽  
A. Suggs ◽  
R. Radhakrishnan ◽  
...  
Keyword(s):  
Yield Stress ◽  
Silicone Oil ◽  
Maximum Yield ◽  
Weight Percent ◽  
High Yield ◽  
Settling Rate ◽  
Mr Fluid ◽  
Carrier Fluid ◽  
Solids Loading ◽  
Mr Fluids

Conventional magnetorheological (MR) fluids are suspensions of micron sized particles in a hydraulic or silicone oil carrier fluid. Recently, research has been conducted into the advantages of using bidisperse MR fluids, which are mixtures of two different powder sizes in the MR suspension. The MR fluids investigated here use a mixture of conventional micron sized particles and nanometer sized particles. The settling rate of such bidisperse fluids using nanometer sized particles is reduced because thermal convection and Van der Waals forces experienced by the nanometer sized particles compete favorably with gravitational forces. This reduction in the settling rate comes at a cost of a reduction in the maximum yield stress that can be manifested by such an MR fluid at its saturation magnetization. There is a measurable and predictable variation in rheological properties as the weight percent of the nanometer sized particles is increased relative to the weight percent of micron size particles, while maintaining a constant solids loading in the MR fluid samples. All bidisperse fluids tested in this study have a solids loading of 60 weight% (wt%) of Fe particles. This study investigates the effect of increasing the weight percent of 30 nanometer (nominal) Fe particles relative to 30 micron (nominal) Fe particles on rheological characteristics such as yield stress and postyield viscosity. The goal of this study is to find an optimal composition of the bidisperse fluid that provides the best combination of high yield stress and low settling rate based on empirical measurements. The applicability of rheological models, such as the Bingham-plastic and the Hershel Buckley models, to the measured flow curves of these MR fluids is also presented.

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.

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.

Magnetorheological Fluids Behaviour in Tension Loading Mode

2008 ◽  
Vol 47-50 ◽  
pp. 242-245 ◽  
Author(s):  
Saiful Amri Mazlan ◽  
Ahmed Issa ◽  
Abdul Ghani Olabi
Keyword(s):  
Magnetic Field ◽  
Tensile Stress ◽  
Magnetic Particles ◽  
Electrical Current ◽  
High Ratio ◽  
Solid Particles ◽  
Mr Fluid ◽  
Carrier Fluid ◽  
Mr Fluids ◽  
Water Based

In this paper, the behaviours of three types of MR fluids under quasi-static loadings in tension mode were investigated. One type of water-based and two types of hydrocarbon-based MR fluids were activated by a magnetic field generated by a coil using a constant value of DC electrical current. Experimental results in terms of stress-strain relationships showed that the MR fluids had distinct unique behaviours during the tension process. A high ratio of solid particles to carrier liquid in the MR fluid is an indication of high magnetic properties. The water-based MR fluid had a relatively large solid-to-liquid ratio. At a given applied current, a significant increase in tensile stress was obtained in this fluid type. On the other hand, the hydrocarbon-based MR fluids had relatively lower solid to liquid ratios, whereby, less increases in tensile stress were obtained. The behaviours of MR fluids were dependent on the relative movement between the solid magnetic particles and the carrier fluid. A complication occurs because, in the presence of a magnetic field, there will be a tendency of the carrier fluid to stick with the magnetic particle

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.

scholarly journals The Synthesis of Organic Oils Blended Magnetorheological Fluids with the Field-Dependent Material Characterization

2019 ◽  
Vol 20 (22) ◽  
pp. 5766 ◽  
Author(s):  
Rakesh Jinaga ◽  
T. Jagadeesha ◽  
Shreedhar Kolekar ◽  
Seung-Bok Choi
Keyword(s):  
Oleic Acid ◽  
Iron Powder ◽  
Cottonseed Oil ◽  
Rheological Characteristics ◽  
Electrolytic Iron ◽  
Mr Fluid ◽  
Carrier Fluid ◽  
Silicon Oil ◽  
Field Dependent ◽  
Electrolytic Iron Powder

Automation is one of the trending terminologies in the field of engineering to achieve various sensors and actuators such as the hydraulic system. Smart fluid is also one of the hot topics for researchers to develop a type of actuator in many control systems since the fluid’s rheological characteristics can be controlled or tuned by the intensity of the external stimuli. In this work, a new smart fluid of magnetorheological (MR) fluid is proposed and its field-dependent rheological characteristics are experimentally identified. An MR fluid using the carrier fluid as the blend of three different fluids, namely silicon oil, honey, and organic oil is prepared. In addition, two types of natural oils are used, sunflower oil and cottonseed oil. The samples are prepared using the blend as the carrier fluid, electrolytic iron powder coated with guar gum as the dispersed phase, and oleic acid as an additive. The quantity of oleic acid is optimized for 30% by weight of electrolytic iron powder. Two samples based on sunflower and cottonseed oil are synthesized and characterized for shear viscosity and shear stress with respect to shear rate subjected to a variable magnetic field. The blend-based MR fluid shows about 10% improvement over the sedimentation rate of silicon oil-based MR fluid as compared to that to conventional MR fluid. The cottonseed oil blend-based MR fluid performs better than sunflower-based fluid in terms of the viscosity and structure.

scholarly journals Modeling of Magnetorheological Fluids by the Discrete Element Method

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Mickaël Kargulewicz ◽  
Ivan Iordanoff ◽  
Victor Marrero ◽  
John Tichy
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Discrete Element Method ◽  
Discrete Element ◽  
Magnetic Interactions ◽  
Time Interval ◽  
Mr Fluid ◽  
Carrier Fluid ◽  
Mr Fluids ◽  
Element Method

Magnetorheological (MR) fluids are fluids whose properties vary in response to an applied magnetic field. Such fluids are typically composed of microscopic iron particles (~1-20μm diameter, 20-40% by volume) suspended in a carrier fluid such as mineral oil or water. MR fluids are increasingly proposed for use in various mechanical system applications, many of which fall in the domain of tribology, such as smart dampers and clutches, prosthetic articulations, and controllable polishing fluids. The goal of this study is to present an overview of the topic to the tribology audience, and to develop an MR fluid model from the microscopic point of view using the discrete element method (DEM), with a long range objective to better optimize and understand MR fluid behavior in such tribological applications. As in most DEM studies, inter-particle forces are determined by a force-displacement law and trajectories are calculated using Newton’s second law. In this study, particle magnetization and magnetic interactions between particles have been added to the discrete element code. The global behavior of the MR fluid can be analyzed by examining the time evolution of the ensemble of particles. Microscopically, the known behavior is observed: particles align themselves with the external magnetic field. Macroscopically, averaging over a number of particles and a significant time interval, effective viscosity increases significantly when an external magnetic field is applied. These preliminary results would appear to establish that the DEM is a promising method to study MR fluids at the microscopic and macroscopic scales as an aid to tribological design.

Enhance the Yield Shear Stress of Magnetorheological Fluids

2001 ◽  
Vol 15 (06n07) ◽  
pp. 549-556 ◽  
Author(s):  
X. TANG ◽  
X. ZHANG ◽  
R. TAO
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Yield Stress ◽  
Chain Structure ◽  
Single Chain ◽  
Compression Pressure ◽  
Sem Images ◽  
Mr Fluid ◽  
Mr Fluids ◽  
Yield Shear Stress

To enhance the yield shear stress of magnetorheological (MR) fluids is an important task. Since thick columns have a yield stress much higher than a single-chain structure, we enhance the yield stress of an MR fluids by changing the microstructure of MR fluids. Immediately after a magnetic field is applied, we compress the MR fluid along the field direction. SEM images show that the particle chains are pushed together to form thick columns. The shear force measured after the compression indicates that the yield stress can reach as high as 800 kPa under a moderate magnetic field, while the same MR fluid has a yield stress of 80 kPa without compression. This enhanced yield stress increases with the magnetic field and compression pressure and has an upper limit well above 800 kPa. The method is also applicable to electrorheological fluids.

The effect of mesocarbon microbeads on magnetorheological fluid behavior

2021 ◽  
pp. 1045389X2110191
Author(s):  
Rebecca Pierce ◽  
Young-Tai Choi ◽  
Norman M Wereley
Keyword(s):  
Yield Stress ◽  
Volume Fraction ◽  
Iron Particle ◽  
Flow Mode ◽  
Shear Mode ◽  
Carrier Fluid ◽  
Hollow Glass ◽  
Mesocarbon Microbeads ◽  
Mr Fluids ◽  
Yield Force

Magnetorheological (MR) fluids are composed of magnetizeable particles suspended in a carrier fluid and change apparent viscosity upon the application of a magnetic field. Previous studies have shown that passive particles, such as hollow glass spheres, can augment the yield stress of MR fluids, but this yield stress augmentation has limited endurance because the hollow glass microspheres are not sufficiently durable. This study evaluates mesocarbon microbeads (MCMBs) as an alternative passive particle with the potential for MR yield force augmentation but with greater durability. The yield properties of six MR fluid concentrations with varying carbonyl iron particle (CIP) and MCMB volume fractions were tested using a shear mode rheometer and flow mode MR damper. MCMBs did not augment yield stress in shear mode, but, in contrast, in flow mode, the yield force increased nonlinearly with MCMB volume fraction. Furthermore, this yield force-enhancing effect did not diminish over 100,000 cycles (or 5 km of piston travel). The theoretical non-dimensional plug thickness which arises from an approximate parallel plate analysis of a fluid element in flow mode is used illustrate to a potential mechanism for the yield force augmentation effect.

Field-On Versus Field-Off Characteristics of Magnetorheological Fluids With an Application in Prosthetic Devices

2011 ◽  
Author(s):  
Ketill H. Gudmundsson ◽  
Fjola Jonsdottir ◽  
Freygardur Thorsteinsson
Keyword(s):  
Knee Joint ◽  
Yield Stress ◽  
Solid Loading ◽  
Fluid Composition ◽  
Shear Yield Stress ◽  
Mr Fluid ◽  
Prosthetic Devices ◽  
Prosthetic Knee ◽  
Mr Fluids ◽  
Shear Yield

The study presents an experimental investigation into the trade-offs between field-on versus field-off rheological characteristics of magnetorheological (MR) fluids. This is relevant in a particular application in prosthetic devices where field-off characteristics are of equal importance to the field-on rheological characteristics. The paper introduces a biomechanical prosthetic knee joint that uses an MR fluid to actively control its rotary stiffness while an amputee walks. The knee is a synergy of artificial intelligence, advanced sensors and MR actuator technology. The knee joint is equipped with an MR rotary brake, utilizing the fluid in direct-shear mode. The MR fluid has response time in the order of milliseconds, making it possible to vary the knee’s stiffness in real-time, depending on sensors data. The field-on characteristics of the employed MR fluid define the rigidness of the knee joint while the field-off characteristics define its flexibility in the absence of a magnetic field. Five MR fluid compositions are prepared, each with a different solid loading ranging from 0.25 to 0.35, by volume. All fluids employ a commercially available carbonyl iron powder and a base fluid. The MR fluids are experimentally evaluated in a rheometer, where both field-off and field-on characteristics are measured. An MR fluid figure of merit function is introduced which is used to rate the selected MR fluids for a potential application in the MR prosthetic knee. An MR fluid composition is sought with the highest ratio between the field-on shear yield stress and the off-state viscosity. The research shows the off-state viscosity to decrease faster than the field-on shear yield stress when reducing the solid loading from 0.35 to 0.25. This suggests that an optimum solid loading exists with regards to the defined merit function. The off-state viscosity of suspensions is known to be exponentially dependent on solid loading while the field-on shear-yield stress is known to sub-quadratically dependent on solid loading. Field-on and field-off models are presented from literature. The models compared to the experimental data and used to theoretically predict the optimum solid loading with regards to field-on shear yield stress and off-state viscosity. As a result of the experimental and the theoretical analysis, a prominent MR fluid composition is selected for a potential application in the MR prosthetic knee. This has been shown to help in the development of prosthetic devices and furthering the success of an MR prosthetic knee joint.

Sign in / Sign up

Export Citation Format

Share Document