Influence of magnetic field, magnetic particle percentages, and particle diameters on the stiffness of magnetorheological fluids

2020 ◽  
Vol 31 (20) ◽  
pp. 2312-2325
Author(s):  
Wei Sun ◽  
Jingjun Yu ◽  
Yueri Cai
Keyword(s):  
Magnetic Field ◽  
Magnetic Particles ◽  
Magnetic Particle ◽  
Random Distribution ◽  
Magnetic Field Intensity ◽  
Variable Stiffness ◽  
Magnetorheological Fluid ◽  
Physical Transformation ◽  
Change State ◽  
The Magnetic Field

Generally, variable stiffness joints of soft robots are generally fabricated using thermoplastics and elastomers due to their ability to change state from rigid to flexible and vice versa. However, these materials require a considerable amount of time to change states and are associated with other technical drawbacks. We demonstrate the instantaneous physical transformation of a Ga-based magnetorheological fluid called Gallistan from a liquid to a viscoelastic solid, and precisely controlled within milliseconds under an applied magnetic field. We studied the magnetic properties of a magnetorheological fluid by dispersing Fe particles in a Ga–In–Sn eutectic alloy. Theoretical analysis of the movement of two particles under magnetic field and typical defects in dipolar chains is studied. The experimental results showed a reversible change in Young’s modulus depending not only on the magnetic field intensity but also the percentage of magnetic particles. Thus, we confirm that the arrangement of magnetic particles transition from random distribution to stable chain structures in the magnetic field. Based on the bi-material nested cantilever beam, the variable stiffness joints can also be precisely adjusted under a magnetic field. In future, this property of the magnetorheological fluid will help develop a variable stiffness joint for soft robotics.

Magnetorheological fluid based on amorphous Fe-Si-B alloy magnetic particles

2021 ◽  
pp. 1045389X2110643
Author(s):  
Chuncheng Yang ◽  
Zhong Liu ◽  
Xiangyu Pei ◽  
Cuiling Jin ◽  
Mengchun Yu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Rheological Property ◽  
Magnetic Particles ◽  
Annealing Treatment ◽  
Magnetorheological Fluid ◽  
The Stability ◽  
The Magnetic Field ◽  
Amorphous Particle ◽  
Better Than

Magnetorheological fluids (MRFs) based on amorphous Fe-Si-B alloy magnetic particles were prepared. The influence of annealing treatment on stability and rheological property of MRFs was investigated. The saturation magnetization ( Ms) of amorphous Fe-Si-B particles after annealing at 550°C is 131.5 emu/g, which is higher than that of amorphous Fe-Si-B particles without annealing. Moreover, the stability of MRF with annealed amorphous Fe-Si-B particles is better than that of MRF without annealed amorphous Fe-Si-B particles. Stearic acid at 3 wt% was added to the MRF2 to enhance the fluid stability to greater than 90%. In addition, the rheological properties demonstrate that the prepared amorphous particle MRF shows relatively strong magnetic responsiveness, especially when the magnetic field strength reaches 365 kA/m. As the magnetic field intensified, the yield stress increased dramatically and followed the Herschel-Bulkley model.

Study on the Magnetic Abrasive Finishing Process Using an Alternating Magnetic Field - Discussion on the Application of Full-Wave Rectifier Current -

2021 ◽  
Vol 1018 ◽  
pp. 117-122
Author(s):  
Hui Jun Xie ◽  
Yan Hua Zou
Keyword(s):  
Magnetic Field ◽  
Magnetic Particles ◽  
Magnetic Particle ◽  
Average Diameter ◽  
Alternating Current ◽  
Particle Sizes ◽  
Full Wave ◽  
Finishing Process ◽  
Abrasive Finishing ◽  
The Magnetic Field

To further improve the finishing efficiency, it has been proposed to apply full-wave rectified current to the coil. In this paper, the effect of full-wave rectified current on the magnetic field and finishing force is studied. The effects of full-wave rectified current and alternating current on finishing characteristics were compared through experiments. The experimental results show that, with different magnetic particle sizes, the finishing efficiency shows different results. In the case of full-wave rectified current, when the average diameter of the magnetic particles is 30 μm, 75 μm and 149 μm, the finishing efficiency is higher than the alternating current, and when the average diameter of the magnetic particles is 330 μm, the finishing efficiency is lower than the alternating current.

Experimental study on tensile mechanical properties of magnetorheological fluid

2020 ◽  
Vol 34 (08) ◽  
pp. 2050070
Author(s):  
Weicheng Wang ◽  
Yiping Luo ◽  
Meng Ji
Keyword(s):  
Magnetic Field ◽  
Mechanical Properties ◽  
Tensile Stress ◽  
Magnetic Particles ◽  
Surface Characteristics ◽  
Magnetorheological Fluid ◽  
Maximum Tensile Stress ◽  
High Permeability ◽  
Soft Magnetic ◽  
The Magnetic Field

Magnetorheological fluid (MRF) is a kind of suspension composed of a nonconducting magnetic liquid and small soft magnetic particles with high permeability and low hysteresis. The tensile mechanical properties of MRF reflect its important mechanical properties. In this study, a testing device is designed to investigate the tensile mechanical properties of MRF in accordance with the plate method theory. First, the magnetic field is selected to analyze the influence of different gap sizes on the magnetic field. The magnetic field strength decreases as the gap increases. Second, a testing platform for tensile mechanical properties is built, and the tensile mechanical properties of MRF are experimentally studied under different magnetic field strengths, tensile speeds and surface characteristics. Experimental results show that the stronger the magnetic field, the greater the tensile yield stress. The maximum tensile stress at different velocities is nearly the same. Different surface characteristics affect tensile stress.

Magnetite/Hydroxyapatite Composite Particles-Assisted Pore Alignment of Tilapia Fish Scale Collagen-Based Scaffold

2016 ◽  
Vol 696 ◽  
pp. 121-128 ◽  
Author(s):  
Vincent Irawan ◽  
Tomomei Sugiyama ◽  
Toshiyuki Ikoma
Keyword(s):  
Magnetic Field ◽  
Magnetic Particles ◽  
Collagen Fiber ◽  
Magnetic Particle ◽  
Ice Crystals ◽  
Composite Particles ◽  
Fish Scale ◽  
Particle Movement ◽  
Hydroxyapatite Composite ◽  
The Magnetic Field

Pore alignment is a vital step to obtain bone-mimicking microstructure in collagen-based scaffold. The porous structure can be controlled by altering the configuration of ice crystals formed in collagen solution. In this study, movements of magnetite/hydroxyapatite composite particles were used to alter the configuration of pore alignment formed in 1.0 and 1.5wt% collagen solutions (HCol 1.0 and HCol 1.5 respectively) by applying moving external magnetic field. In case of HCol 1.0 pores were aligned parallel to the magnetic field, while for HCol 1.5 pores were aligned at curve shape. Different results of pore alignment were thought to originate from differences in collagen fiber alignment caused by magnetic particles movement paths. This result thus opens up the possibility of controlling pore alignment by utilizing magnetic particle movement.

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

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.

Viscosity Control of Magnetorheological Fluid by Power Saving Magnetizing Mechanism Using Movement of Permanent Magnet

2020 ◽  
Vol 32 (5) ◽  
pp. 977-983
Author(s):  
Jumpei Kawasaki ◽  
Yuki Nakamura ◽  
Yasukazu Sato ◽  
◽  
Keyword(s):  
Magnetic Field ◽  
Power Consumption ◽  
Permanent Magnet ◽  
Electric Power ◽  
Field Intensity ◽  
Magnetic Field Intensity ◽  
Magnetic Circuit ◽  
Angular Position ◽  
Magnetorheological Fluid ◽  
The Magnetic Field

Generally, the magnetic field applied to a magnetorheological fluid (MRF) is generated by electromagnets. Electromagnets consume electric power during MRF magnetization, which is an issue. In this study, we examine two kinds of magnetizing mechanism using a permanent magnet, instead of electromagnets, to save electric power and generate a magnetic field on the MRF. One mechanism linearly moves the permanent magnet into the magnetic circuit composed of yokes. The magnetic field intensity on the MRF is then controlled by changing the overlap between the magnet and the yokes. The other mechanism rotates a permanent magnet in the magnetic circuit. The magnetic field intensity on the MRF is then controlled by changing the relative angular position between the magnet and the yokes. These two mechanisms normally generate force or torque on the magnet toward a magnetically stable position concerning the magnet, and the force or torque causes power consumption to hold and move the magnet. We design herein special magnetic circuits and a cancelation mechanism for the force or torque that drastically reduce the power consumption during the MRF magnetization compared with an electromagnet-type magnetizing device.

scholarly journals Optical Imaging of Magnetic Particle Cluster Oscillation and Rotation in Glycerol

2021 ◽  
Vol 7 (5) ◽  
pp. 82
Author(s):  
River Gassen ◽  
Dennis Thompkins ◽  
Austin Routt ◽  
Philippe Jones ◽  
Meghan Smith ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Particles ◽  
Magnetic Particle ◽  
Barium Hexaferrite ◽  
Optical Microscope ◽  
Simplified Model ◽  
Particle Cluster ◽  
Average Deviation ◽  
Cross Sectional

Magnetic particles have been evaluated for their biomedical applications as a drug delivery system to treat asthma and other lung diseases. In this study, ferromagnetic barium hexaferrite (BaFe12O19) and iron oxide (Fe3O4) particles were suspended in water or glycerol, as glycerol can be 1000 times more viscous than water. The particle concentration was 2.50 mg/mL for BaFe12O19 particle clusters and 1.00 mg/mL for Fe3O4 particle clusters. The magnetic particle cluster cross-sectional area ranged from 15 to 1000 μμm2, and the particle cluster diameter ranged from 5 to 45 μμm. The magnetic particle clusters were exposed to oscillating or rotating magnetic fields and imaged with an optical microscope. The oscillation frequency of the applied magnetic fields, which was created by homemade wire spools inserted into an optical microscope, ranged from 10 to 180 Hz. The magnetic field magnitudes varied from 0.25 to 9 mT. The minimum magnetic field required for particle cluster rotation or oscillation in glycerol was experimentally measured at different frequencies. The results are in qualitative agreement with a simplified model for single-domain magnetic particles, with an average deviation from the model of 1.7 ± 1.3. The observed difference may be accounted for by the fact that our simplified model does not include effects on particle cluster motion caused by randomly oriented domains in multi-domain magnetic particle clusters, irregular particle cluster size, or magnetic anisotropy, among other effects.

scholarly journals Magnetotaxis as a Means for Nanofabrication

2014 ◽  
Vol 23 (01n02) ◽  
pp. 1450008
Author(s):  
Isaac Macwan ◽  
Zihe Zhao ◽  
Omar Sobh ◽  
Jinnque Rho ◽  
Ausif Mahmood ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Semiconductor Manufacturing ◽  
Magnetic Field Intensity ◽  
Magnetotactic Bacteria ◽  
Semiconductor Substrate ◽  
Field Lines ◽  
A Chain ◽  
Magnetospirillum Magneticum ◽  
The Magnetic Field

Magnetotactic bacteria (MTB), discovered in early 1970s contain single-domain crystals of magnetite ( Fe 3 O 4) called magnetosomes that tend to form a chain like structure from the proximal to the distal pole along the long axis of the cell. The ability of these bacteria to sense the magnetic field for displacement, also called magnetotaxis, arises from the magnetic dipole moment of this chain of magnetosomes. In aquatic habitats, these organisms sense the geomagnetic field and traverse the oxic-anoxic interface for optimal oxygen concentration along the field lines. Here we report an elegant use of MTB where magnetotaxis of Magnetospirillum magneticum (classified as AMB-1) could be utilized for controlled navigation over a semiconductor substrate for selective deposition. We examined 50mm long coils made out of 18AWG and 20AWG copper conductors having diameters of 5mm, 10mm and 20mm for magnetic field intensity and heat generation. Based on the COMSOL simulations and experimental data, it is recognized that a compound semiconductor manufacturing technology involving bacterial carriers and carbon-based materials such as graphene and carbon nanotubes would be a desirable choice in the future.

scholarly journals Distributed variable stiffness joint assist mechanism based on laminated structure

2021 ◽  
Vol 18 (6) ◽  
pp. 172988142110606
Author(s):  
Zhenquan Fan ◽  
Xiaoyu Wang ◽  
Zijin Wang ◽  
Sijia Gao ◽  
Sheng Lin
Keyword(s):  
Magnetic Field ◽  
Stiffness Matrix ◽  
Variable Stiffness ◽  
Drive Unit ◽  
Joint Power ◽  
Laminated Structure ◽  
Giant Magnetostrictive Material ◽  
In Series ◽  
Field Excitation ◽  
The Magnetic Field

Exoskeleton technology is more and more widely used in military, human rehabilitation, and other fields, but exoskeleton assisting mechanisms have problems such as high quality, concentrated driving sources, and poor flexibility. This article proposes a distributed variable stiffness joint power-assisted mechanism based on a laminated structure, which uses a giant magnetostrictive material as the driving source and the variable stiffness source of the structure. The distributed driving is realized by multiple driving units connected in series and parallel. Firstly, the drive unit stiffness matrix is deduced, and the expression equations of the cascaded total stiffness matrix of the drive module are obtained. After the simulation study, the curve of the stiffness of a single drive unit with a magnetic field and the stiffness of multiple drive units connected in series and parallel are in the absence of the magnetic field. The change curve of the stiffness of the booster module with the number of drive units under the excitation and saturation magnetic field excitation conditions is to achieve the effect of dynamically controlling the structural stiffness of the drive unit by controlling the size of the magnetic field and to obtain a general formula through data fitting. The number of drive units required under a fixed magnetic field excitation can ensure that the error is within 5%. The research results lay the foundation for further analysis of the distributed variable stiffness joint assist technology.

scholarly journals Magnetorheological Fluids Behaviour in Oscillatory Compression Squeeze: Experimental Testing and Analysis

2019 ◽  
Vol 13 (4) ◽  
pp. 221-225
Author(s):  
Wojciech Horak ◽  
Marcin Szczęch ◽  
Bogdan Sapiński
Keyword(s):  
Magnetic Field ◽  
Volume Fraction ◽  
Experimental Testing ◽  
Magnetic Field Gradient ◽  
Particle Volume Fraction ◽  
Excitation Frequency ◽  
Magnetorheological Fluid ◽  
Density Level ◽  
Particle Volume ◽  
The Magnetic Field

Abstract This article deals with experimental testing of magnetorheological fluid (MRF) behaviour in the oscillatory squeeze mode. The authors investigate and analyse the influence of excitation frequency and magnetic field density level on axial force in MRFs that differ in particle volume fraction. The results show that, under certain conditions, the phenomenon of self-sealing can occur as a result of the magnetic field gradient and a vacuum in the working gap of the system.

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