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

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.

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Shear and Squeeze Rheometry of Magnetorheological Fluids

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.305.344 ◽

2011 ◽

Vol 305 ◽

pp. 344-347 ◽

Cited By ~ 3

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.

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

Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Integrated System Design and Implementation ◽

10.1115/smasis2013-3244 ◽

2013 ◽

Cited By ~ 6

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.

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A Unified Approach for Flow Analysis of Magnetorheological Fluids

Journal of Applied Mechanics ◽

10.1115/1.4003346 ◽

2011 ◽

Vol 78 (4) ◽

Cited By ~ 6

Author(s):

Barkan Kavlicoglu ◽

Faramarz Gordaninejad ◽

Xiaojie Wang

Keyword(s):

Experimental Study ◽

Channel Flow ◽

Pressure Loss ◽

Flow Analysis ◽

Surface Topology ◽

Shear Yield Stress ◽

Mr Fluid ◽

Mr Fluids ◽

Channel Surface ◽

Shear Yield

This study presents a new approach for flow analysis of magnetorheological (MR) fluids through channels with various surface topologies. Based on an experimental study an analytical method is developed to predict the pressure loss of a MR fluid as a function of the applied magnetic field strength, volumetric flow rate, and surface topology, without utilizing the concept of shear yield stress. A channel flow rheometer with interchangeable channel walls is built to demonstrate that the pressure loss across the MR fluid flow channel is significantly affected by the channel surface properties. Based on the experimental study it is concluded that a unique shear yield stress cannot be defined for a given MR fluid, since its pressure drop depends on the surface topology of the device. Therefore, a relation for nondimensional friction factor associated with MR fluid channel flow is developed in terms of a modified Mason number and dimensionless surface topology parameters. Using the nondimensional model, the pressure loss for various magnetic fields and volumetric flow rates can be represented by a single master curve for a given channel surface topology without the assumption of a constitutive model for MR fluids.

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FRICTION FACTOR OF MAGNETO-RHEOLOGICAL FLUID FLOW IN GROOVED CHANNELS

International Journal of Modern Physics B ◽

10.1142/s0217979205030219 ◽

2005 ◽

Vol 19 (07n09) ◽

pp. 1297-1303 ◽

Cited By ~ 3

Author(s):

F. GORDANINEJAD ◽

B. M. KAVLICOGLU ◽

X. WANG

Keyword(s):

Fluid Flow ◽

Friction Factor ◽

Shear Yield Stress ◽

Mr Fluid ◽

Flow Rates ◽

Mr Fluids ◽

Mason Number ◽

Shear Yield ◽

Grooved Surface ◽

Magneto Rheological

The focus of this work is to study surface effects on the friction factor a magneto-rheological (MR) fluid flowing through a grooved channel under various magnetic fields and volumetric flow rates. Based on the experimental data, a relation is developed for the friction factor of MR fluid in channel flow in terms of Mason number evaluated at the surface, and the depth of the grooves. Using this relation, the pressure loss of a MR fluid flowing through a channel with grooved walls can be determined without implementing a constitutive model for MR fluids or utilizing the concept of shear yield stress. Several grooves with different configurations in channel walls have been considered. From the experimental results it has been demonstrated that under an applied magnetic field, the grooved surface would increase the friction factor of MR fluid flow significantly when comparing to the surface without grooving. The depth of grooves plays an important role in this increment.

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The shear and compressive yield stress of fibrillated acacia pulp fiber suspensions

Nordic Pulp & Paper Research Journal ◽

10.1515/npprj-2019-0065 ◽

2020 ◽

Vol 35 (2) ◽

pp. 243-250

Author(s):

Jiulong Sha ◽

Yueyue Yang ◽

Can Wang ◽

Wei Li ◽

Peng Lu ◽

...

Keyword(s):

Yield Stress ◽

Paper Industry ◽

Pulp Fiber ◽

Fiber Suspensions ◽

Fiber Morphology ◽

Shear Yield Stress ◽

Geometrical Properties ◽

Compressive Yield Stress ◽

Shear Yield ◽

Fiber Cell Wall

AbstractThe degree of interactions between fibers and the tendency of fibers to form flocs play an important role in effective unit operation in pulp and paper industry. Mechanical treatments may damage the structure of the fiber cell wall and geometrical properties, and ultimately change the fiber-fiber interactions. In this study, the gel crowding number, compressive and shear yield stress of fibrillated acacia pulps were investigated, and the results showed that the gel crowding number of the refined pulp samples ranged from 8.7 to 10.7, which were much lower than that of un-refined pulps. As the concentration increased, both the compressive yield stress {P_{y}} and shear yield stress {\tau _{y}} of all suspensions increased accordingly, and the yield stress was found to depend on a power law of the crowding number. Moreover, the values of {\tau _{y}}/{P_{y}} were also examined and the variation of {\tau _{y}}/{P_{y}} became largely dependent on the fiber morphology and mass concentration.

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Shear yield stress of partially flocculated colloidal suspensions

AIChE Journal ◽

10.1002/aic.690440305 ◽

1998 ◽

Vol 44 (3) ◽

pp. 538-544 ◽

Cited By ~ 137

Author(s):

Peter J. Scales ◽

Stephen B. Johnson ◽

Thomas W. Healy ◽

Prakash C. Kapur

Keyword(s):

Yield Stress ◽

Colloidal Suspensions ◽

Shear Yield Stress ◽

Shear Yield

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HYSCOM KNEE, A PROSTHETIC KNEE JOINT WITH STANCE AND SWING MOTION CONTROL SYSTEM UTILIZING COMPACT MR FLUID BRAKE

Electro-Rheological Fluids and Magneto-Rheological Suspensions ◽

10.1142/9789814340236_0017 ◽

2011 ◽

Cited By ~ 1

Author(s):

YUICHI HIKICHI ◽

MASAMI NAKANO ◽

TEPPEI TSUJITA

Keyword(s):

Control System ◽

Knee Joint ◽

Motion Control ◽

Motion Control System ◽

Mr Fluid ◽

Prosthetic Knee ◽

Prosthetic Knee Joint

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MAGNETORHEOLOGICAL FLUIDS AND THEIR PROPERTIES

International Journal of Modern Physics B ◽

10.1142/s0217979205029110 ◽

2005 ◽

Vol 19 (01n03) ◽

pp. 593-596 ◽

Cited By ~ 3

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.

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