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.

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.

Experiments and Models of the Magneto Rheological Behavior of High Weight Percent Suspensions of Carbonyl Iron Particles in Silicone Oil

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
Farzad Ahmadkhanlou ◽  
Monon Mahboob ◽  
Stephen Bechtel ◽  
Gregory Washington
Keyword(s):  
Kinetic Theory ◽  
First Principles ◽  
Mechanical Response ◽  
Silicone Oil ◽  
Three Dimensional ◽  
Magnetic Behavior ◽  
Weight Percent ◽  
Mr Fluid ◽  
Mr Fluids ◽  
Fluid Behavior

Flow properties of magnetorheological (MR) fluids are greatly altered by the application of a magnetic field. The design, optimization, and control of novel devices that exploit MR fluid behavior in multidegree of freedom applications require three dimensional models characterizing the coupling of magnetic behavior to mechanical behavior in MR fluids. The authors have derived 3D MR fluid models based on multiscale kinetic theory. The underlying bases of the models are summarized, with phenomenological empiricism distinguished from multiscale first principles, and the models’ ability to capture the experimentally measured mechanical response of a MR fluid-based damper to specified magnetic fields is assessed. The results of this comparison are that the kinetic theory-based models both relate macroscale MR fluid behavior to a first-principles description of magnetomechanical coupling at the microscale and possess the flexibility to best match the measured behavior of a particular MR fluid device observed in our experiments.

Demonstration of Combined Shear and Squeeze Strengthening Modes in a Searle-Type Magnetorheometer

2013 ◽  
Author(s):  
Andrew C. Becnel ◽  
Norman M. Wereley
Keyword(s):  
Yield Stress ◽  
Energy Absorption ◽  
Shear Yield Stress ◽  
Particle Chain ◽  
Solids Loading ◽  
Mr Fluids ◽  
Shear Yield ◽  
Microstructure Model ◽  
Novel Method ◽  
A Chain

This research details a novel method of increasing the shear yield stress of magnetorheological (MR) fluids by combining shear and squeeze modes of operation to manipulate particle chain structures, to achieve so-called compression-assisted aggregation. The contribution of both active gap separation and particle concentration are experimentally measured using a custom-built Searle cell magnetorheometer, which is a model device emulating a rotary Magnetorheological Energy Absorber (MREA). Characterization data from large (1 mm) and small (250 μm) gap geometries are compared to investigate the effect of the gap on yield stress by compression enhancement. Two MR fluids having different particle concentrations (32 vol% and 40 vol%) are also characterized to demonstrate the effect of solids loading on compression-assisted chain aggregation. Details of the experimental setup and method are presented, and a chain microstructure model is used to explain experimental trends. The torque resisted by practical rotary MREAs is directly related to the strength of the MR fluid used, as measured by the shear yield stress. This study demonstrates that it is feasible, utilizing the compression-enhanced shear yield stress, to either (1) design a rotary MREA of a given volume to achieve higher energy absorption density (energy absorbed normalize by device volume), or (2) reduce the volume of a given rotary MREA to achieve the same energy absorption density.

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.

Synthesis and field dependent shear stress evaluation of stable MR fluid for brake application

2017 ◽  
Vol 69 (5) ◽  
pp. 655-665 ◽  
Author(s):  
Lijesh K.P. ◽  
Deepak Kumar ◽  
Harish Hirani
Keyword(s):  
Shear Stress ◽  
Oleic Acid ◽  
Silicone Oil ◽  
Ammonium Hydroxide ◽  
Iron Particles ◽  
Mr Fluid ◽  
Content Type ◽  
Weight Percentage ◽  
Mr Fluids ◽  
Brake Application

Purpose The purpose of this paper is to report on the development of magnetorheological (MR) fluids, having high on-state shear stress/viscosity, low off-state shear stress/viscosity, good redispersibility and stable suspension of carbonyl iron particles, using tetramethyl ammonium hydroxide (TAH) and oleic acid. Design/methodology/approach MR fluids for use in brakes are synthesized using different weight percentages of silicone oil, TAH, oleic acid and iron particles. The effects of TAH and oleic acid are studied. Shear stress is measured as a function of magnetic field on a magneto-rheometer. The images of MR particles settling with time are presented. The test set-up used to evaluate the performance of the MR fluids synthesized for brake application is detailed. Finally, a significant improvement in the MR performance of brakes is reported. Findings The MR fluid having 0.25 Wt.% oleic acid showed low off-state viscosity/shear stress and high on-state viscosity/shear stress. A higher weight percentage of TAH in the MR fluid further reduced the low off-shear stress and increased the high on-state shear stress with better stability. Originality/value Improvement of MR brake performance by adding surfactants like TAH and oleic acid has been the subject matter of several studies in the past, but these studies used a fixed percentage of surfactants in MR fluids. In the present work, the optimum percentage of TAH and oleic acid for an improved braking performance is determined by varying their content in the MR fluid, which has not been reported in any other work thus far.

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 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.

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