Quasi-Static Rheological Properties of Lithium-Based Magnetorheological Grease under Large Deformation

This paper investigates the quasi-static rheological properties of lithium-based magnetorheological (MR) grease under large deformation. Three types of lithium-based MR grease comprising different mass ratios of carbonyl iron (CI) particles and lithium-based grease were prepared. The dependence of the magneto-induced stress–strain curves for MR grease on CI particles content, shear rate, and shear deformation under quasi-static monotonic shear conditions were tested and discussed. The results demonstrate that the shear rate dependence of the maximum yield stress is significantly weakened by the magnetic field, and this weakening is further enhanced as the CI particles content of MR grease increases. In addition, to evaluate and characterize the behavior of the cyclic shear–stress curves of MR grease under quasi-static condition, cyclic shear tests under different controlled conditions, i.e., CI particles content, shear rate, shear strain amplitude, and magnetic field strength, were conduct and analyzed. The magneto-induced shear stress of MR grease with higher CI particles content shows a sharp decrease during the transition from loading to unloading. Moreover, the experiment results also show that the damping characteristics of MR grease are highly correlated with CI particles content, shear strain, and magnetic field strength.

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Investigation of the Rheological Properties of Zn-Ferrite/Perfluoropolyether Oil-Based Ferrofluids

Nanomaterials ◽

10.3390/nano11102653 ◽

2021 ◽

Vol 11 (10) ◽

pp. 2653

Author(s):

Fang Chen ◽

Xiaobing Liu ◽

Zhenggui Li ◽

Shengnan Yan ◽

Hao Fu ◽

...

Keyword(s):

Magnetic Field ◽

Shear Rate ◽

Field Strength ◽

Rheological Properties ◽

Temperature Variation ◽

Magnetic Field Strength ◽

Theoretical Research ◽

Precipitation Method ◽

Zn Ferrite ◽

Co Precipitation

The rheological properties of ferrofluids are related to various applications, such as sealing and loudspeakers, and have therefore attracted widespread attention. However, the rheological properties and their influence on the mechanisms of perfluoropolyether oil (PFPE oil)-based ferrofluids are complicated and not clear. Here, a series of PFPE oil-based ferrofluids were synthesized via a chemical co-precipitation method, and their rheological properties were revealed, systematically. The results indicate that the prepared Zn-ferrite particles have an average size of 12.1 nm, within a range of 4–18 nm, and that the ferrofluids have excellent dispersion stability. The activity of the ferrofluids changes from Newtonian to non-Newtonian, then to solid-like with increasing w from 10 wt% to 45.5 wt%, owing to their variation in microstructures. The viscosity of the ferrofluids increases with increasing Mw (the molecular weight of base liquid PFPE oil polymer), attributed to the increase in entanglements between PFPE oil molecules. The magnetization temperature variation of Zn-ferrite nanoparticles and viscosity temperature variation of PFPE oil together contribute to the viscosity temperature change in ferrofluids. The viscosity of the ferrofluids basically remains unchanged when shear rate is above 50 s−1, with increasing magnetic field strength; however, it first increases and then levels off when the rate is under 10 s−1, revealing that the shear rate and magnetic field strength together affect viscosity. The viscosity and its alteration in Zn-ferrite/PFPE oil-based ferrofluids could be deduced through our work, which will be greatly significant in basic theoretical research and in various applications.

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Magneto-induced rheological properties of magnetorheological gel under quasi-static shear with large deformation

RSC Advances ◽

10.1039/d0ra05843b ◽

2020 ◽

Vol 10 (53) ◽

pp. 31691-31704

Author(s):

Runsong Mao ◽

Huixing Wang ◽

Guang Zhang ◽

Xudan Ye ◽

Jiong Wang

Keyword(s):

Magnetic Field ◽

Shear Rate ◽

Energy Dissipation ◽

Shear Strain ◽

Rheological Properties ◽

Large Deformation ◽

Strain Amplitude ◽

Magnetic Particles ◽

Static Shear ◽

Shear Strain Amplitude

Magnetorheological gel is a material composed of magnetic particles and polyurethane. CIPs content, shear rate, shear strain amplitude and magnetic field affect damping performance. The magento-induced enhancement of energy dissipation density of MRG-60 could reach 104900%.

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Modeling and Verification of Relaxation Behavior for Magnetorheological Elastomers with Applied Magnetic Field

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.730.527 ◽

2017 ◽

Vol 730 ◽

pp. 527-532 ◽

Cited By ~ 2

Author(s):

Guo Jun Yu ◽

Xiao Guo Lin ◽

Fei Guo

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Shear Strain ◽

Magnetic Field Strength ◽

Relaxation Modulus ◽

Relaxation Behavior ◽

Rubber Matrix ◽

Magnetorheological Elastomers ◽

The Magnetic Field

In this paper, on the basis of the viscoelastic fractional derivative model, Mittag-Leffler function is applied to deduce the expression of stress relaxation modulus for magnetorheological elastomers according to its form and main properties. Furthermore, the relaxation modulus for polyurethane rubber matrix cured magnetorheological elastomers at different applied magnetic fields and shear strains is tested by rheometer. The results indicate that magnetorheological elastomers exhibit obvious relaxation behavior and the magnetic field strength and shear strain exert significant influence on the relaxation behavior: the relaxation modulus of magnetorheological elastomers increases with the magnetic field strength but decreases with the shear strain. Besides, the model agrees well with the experimental data which indicates that the model is suitable for characterization of relaxation behavior for magnetorheological elastomers.

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YIELD STRESS IN FERROFLUIDS?

International Journal of Modern Physics B ◽

10.1142/s0217979207045694 ◽

2007 ◽

Vol 21 (28n29) ◽

pp. 4806-4812 ◽

Cited By ~ 21

Author(s):

HAMID SHAHNAZIAN ◽

STEFAN ODENBACH

Keyword(s):

Magnetic Field ◽

Shear Stress ◽

Field Strength ◽

Yield Stress ◽

Magnetic Field Strength ◽

Theoretical Investigations ◽

Field Dependent ◽

Special Stress ◽

Viscoelastic Effects ◽

The Magnetic Field

Recent experimental as well as theoretical investigations have shown that the formation of structures of magnetic nanoparticles has significant influence on the behaviour of ferrofluids. The dependence of this structure formation on the magnetic field strength and shear stress applied to the fluid leads to strong changes of the viscosity and to the appearance of viscoelastic effects in the fluids. The actual approaches for a description of the effects vary in the basic modeling of the fluid and its behaviour. Some models base on microscopic assumptions, other model the fluid on a mesoscale and even macroscopic descriptions abstaining from microscopic assumptions have been suggested. A point in which the predictions of the models differ is the question of an appearance of a magnetic field dependent yield stress in ferrofluids. For investigations concerning the appearance and field dependence of a yield stress a special stress controlled rheometer for ferrofluids has been designed. The preliminary results presented here, show a dependence of the yield stress on magnetic field strength for different kind of ferrofluids and magnetorheological fluids.

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MR Fluid Behavior Under Constant Shear Rates and High Magnetic Fields Over Long Time Periods

Aerospace ◽

10.1115/imece2004-61726 ◽

2004 ◽

Cited By ~ 1

Author(s):

Constantin Ciocanel ◽

Kevin Molyet ◽

Hideki Yamamoto ◽

Sheila L. Vieira ◽

Nagi G. Naganathan

Keyword(s):

Magnetic Field ◽

Shear Rate ◽

Shear Strain ◽

Rheological Properties ◽

Smart Materials ◽

Shear Stresses ◽

Mr Fluid ◽

Shear Rates ◽

Constant Shear ◽

Mechanical Devices

MR fluids are smart materials that reversibly change their rheological properties in the presence of a magnetic field. Their capability to support a high range of shear stresses makes them an ideal component of many mechanical devices. However, to be suitable for applications requiring a large number of cycles, e.g. a clutch, the long term behavior of these fluids needs to be thoroughly investigated and well understood. The paper presents a new MR cell design along with a study of the shear rate, shear strain, magnetic field and time influences on the properties and behavior of a MR fluid tested for long periods of time. The MR cell is required to adapt a commercially available rheometer to measure the rheological properties of the fluid. Overall characteristics of the designed MR cell output capability are provided. Constant shear rate tests, two hours in duration, have been performed at shear rates between 0.1 and 200 l/s under magnetic field intensities up to 0.4 T. The rheological measurements indicated that the time, the shear strain and the shear rate influence the fluid’s shear stress magnitude.

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Computational Modeling of Non-Newtonian Blood Flow Through Stenosed Arteries in the Presence of Magnetic Field

Journal of Biomechanical Engineering ◽

10.1115/1.4025107 ◽

2013 ◽

Vol 135 (11) ◽

Cited By ~ 12

Author(s):

Aiman Alshare ◽

Bourhan Tashtoush ◽

Hossam H. El-Khalil

Keyword(s):

Magnetic Field ◽

Blood Flow ◽

Shear Stress ◽

Pressure Drop ◽

Wall Shear Stress ◽

Field Strength ◽

Magnetic Field Strength ◽

Stenosed Artery ◽

Flow Through ◽

Wall Shear

Steady flow simulations of blood flow in an axisymmetric stenosed artery, subjected to a static magnetic field, are performed to investigate the influence of artery size, magnetic field strength, and non-Newtonian behavior on artery wall shear stress and pressure drop in the stenosed section. It is found that wall shear stress and pressure drop increase by decreasing artery size, assuming non-Newtonian fluid, and increasing magnetic field strength. In the computations, the shear thinning behavior of blood is accounted for by the Carreau–Yasuda model. Computational results are compared and found to be inline with available experimental data.

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Phase Change and Magneto-Rheology of a Suspension Composed of Magnetic Rod-Like Particles

Volume 7A: Fluids Engineering Systems and Technologies ◽

10.1115/imece2015-51263 ◽

2015 ◽

Author(s):

Akira Satoh

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Phase Change ◽

Rheological Properties ◽

Magnetic Field Strength ◽

Magnetic Particles ◽

Magnetic Particle ◽

Magneto Rheological ◽

Aggregate Structures ◽

The Magnetic Field

Magnetic particle suspensions have a great potential as an application in engineering fields and therefore a variety of studies on these functional fluid have been conducted in various fields, including the traditional fluid engineering field and the recent bioengineering field such as an application to a drug delivery system. The main application target in the fluid engineering field may be mechanical dampers and actuators. Magneto-rheological properties significantly depend on the formation of aggregates of magnetic particles. In the present study, we focus on a ferromagnetic rod-like particle suspension to discuss the phase change of aggregate structures of magnetic rod-like particles and the magneto-rheological properties that are strongly dependent on the formation of aggregate structures. The characteristics of the phase change are mainly investigated by Monte Carlo simulations for thermodynamic equilibrium and the magneto-rheological properties are done by Brownian dynamics simulations in a simple shear flow situation. From the latter simulations, we discuss mainly the dependence of the magneto-rheological effect on the phase change of aggregate structures. In a weak applied magnetic field, magnetic rod-like particles tend to aggregate to form raft-like clusters if the magnetic particle-particle interaction is much stronger than thermal energy. If the magnetic field strength is increased, these raft-like clusters drastically dissociate into single-moving particles at a certain value of the magnetic field strength, that is, the phase change in aggregate structures arises. The net viscosity and viscosity components exhibit complex dependence on the magnetic field strength, which is mainly due to the raft-like cluster formation of magnetic particles.

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On the Configuration of the Magnetic Field of β CrB

International Astronomical Union Colloquium ◽

10.1017/s0252921100080933 ◽

1976 ◽

Vol 32 ◽

pp. 613-622

Author(s):

I.A. Aslanov ◽

Yu.S. Rustamov

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Radial Velocity ◽

Magnetic Field Strength ◽

Complex Shape ◽

Rotation Period ◽

Field Variation ◽

Magnetic Field Variation ◽

Secular Variations ◽

The Magnetic Field

SummaryMeasurements of the radial velocities and magnetic field strength of β CrB were carried out. It is shown that there is a variability with the rotation period different for various elements. The curve of the magnetic field variation measured from lines of 5 different elements: FeI, CrI, CrII, TiII, ScII and CaI has a complex shape specific for each element. This may be due to the presence of magnetic spots on the stellar surface. A comparison with the radial velocity curves suggests the presence of a least 4 spots of Ti and Cr coinciding with magnetic spots. A change of the magnetic field with optical depth is shown. The curve of the Heffvariation with the rotation period is given. A possibility of secular variations of the magnetic field is shown.

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