scholarly journals Effect of Curing Current on Stiffness and Damping Properties of Magnetorheological Elastomers

2018 ◽  
Vol 1 (2) ◽  
pp. 51-58 ◽  
Author(s):  
Norhiwani Hapipi ◽  
Saiful Amri Mazlan ◽  
Siti Aishah Abdul Aziz ◽  
Ubaidillah Ubaidillah ◽  
Seung-Bok Choi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Storage Modulus ◽  
Damping Properties ◽  
Magnetorheological Elastomers ◽  
Three Samples ◽  
Viscoelastic Effects ◽  
Dynamic Performances ◽  
Mr Effect ◽  
Stiffness And Damping ◽  
The Magnetic Field

In this study, the viscoelastic effects of the magnetic field strength imposed for curing process on the stiffness and damping properties of magnetorheological elastomers (MREs) are experimentally investigated. In order to observe the effect, three different samples of MRE are fabricated by imposing curing current of 0.1 A, 0.3 A and 0.5 A which is equivalent to the magnetic field of 70 mT, 309 mT, and 345 mT, respectively. All samples consist of 30% silicone rubber and 70% carbonyl iron particles (CIPs) by weight percentages. After observing the morphological images via SEM, the dynamic performances of these samples, such as storage modulus and loss factor are evaluated and compared as a function of the magnetic field intensity or oscillation frequency. It is shown that the sample cured at 0.5A exhibits the highest storage modulus in the frequency domain. In addition, MR effects of three samples are identified, and it is found that the sample cured at 0.5A shows the highest absolute and relative MR effect.

Stiffness and Damping Properties of (Semi) Floating Ring Bearing Using Magnetorheological Fluids as Lubricant

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Xiaohu Wang ◽  
Hongguang Li ◽  
Wen Lu ◽  
Guang Meng
Keyword(s):  
Magnetic Field ◽  
Shear Rate ◽  
Performance Enhancement ◽  
Magnetorheological Fluids ◽  
Model Parameters ◽  
Damping Properties ◽  
Damping Characteristics ◽  
Stiffness And Damping ◽  
The Magnetic Field ◽  
Thinning Effect

Magnetorheological fluids (MRFs) are applicable for achieving semi-active control in smart bearings. For hydrodynamic bearings lubricated with MRF, changes of the viscosity induced by magnetic field lead to changes of the dynamic characteristics such as stiffness and damping properties, providing the controllability to the bearings in rotor applications. Two main defects of the MRF, however, may potentially limit the use of this kind of bearings. One is that the magnetic field-induced viscosity alteration capability decreases as the shear rate increases; the other is the extra friction introduced by iron particles in the MRF in external magnetic field. In this study, the floating ring bearing (FRB) and semi-floating ring bearing (sFRB) are introduced to replace common journal bearing for MRF-lubricated smart bearings. Performance enhancement is achieved using FRB and sFRB. The lubrication behavior of MRF is studied using the Herschel–Bulkley (HB) model that incorporates the yield stress and the shear-thinning effect, which are the two main features of the MRF under shearing. A kind of MRF is developed for lubrication application, and a test rig is setup to measure its shear rate–stress relationship and then to identify its HB model parameters. With the identified HB model, stiffness and damping characteristics of the MRF-lubricated FRB and sFRB are studied. Results show that, compared to MRF-lubricated common journal bearings, the MRF-lubricated FRB and sFRB both achieve better performances in damping enhancement, while limiting the journal friction to a relatively lower degree.

Damping Properties of Magnetorheological Elastomers

2017 ◽  
Vol 1143 ◽  
pp. 247-252 ◽  
Author(s):  
Petrica Eduard Chirila ◽  
Ionel Chirica ◽  
Elena Felicia Beznea
Keyword(s):  
Magnetic Field ◽  
Smart Materials ◽  
Magnetic Field Induction ◽  
Reactive Force ◽  
Damping Properties ◽  
Magnetorheological Elastomers ◽  
Field Induction ◽  
Field Action ◽  
The Magnetic Field

Magnetorheological elastomers (MREs) are a kind of smart materials, which change the mechanical properties (viscoelastic characteristics) under the magnetic field action. In the paper the determination of damping properties (reactive force) of specimens made out of magnetorheological elastomers is presented. The specimens made out of MREs have been fabricated as a composite with matrix made out of silicone rubber with certain contents of magnetisable particles (carbonyl iron powder). The cylindrical specimens have been tested in compression loading, controlled by an electro-mechanic system. The MRE characteristics of the specimens have been determined in the presence of a magnetic field produced with an electromagnet (coil device). The reactive force occurring in the MRE specimen has been determined on the basis of the measured data during loading. The variation curves of the reactive force versus magnetic field induction are drawn. As a conclusion, the rigidity of the MRE specimen is increasing since the magnitude of the magnetic field induction is increasing.

scholarly journals Magnetorheological Hybrid Elastomers Based on Silicone Rubber and Magnetorheological Suspensions with Graphene Nanoparticles: Effects of the Magnetic Field on the Relative Dielectric Permittivity and Electric Conductivity

2019 ◽  
Vol 20 (17) ◽  
pp. 4201 ◽  
Author(s):  
Bica ◽  
Bunoiu
Keyword(s):  
Magnetic Field ◽  
Dielectric Permittivity ◽  
Silicone Rubber ◽  
Silicone Oil ◽  
Relative Dielectric Permittivity ◽  
Magnetorheological Elastomers ◽  
Magnetorheological Suspensions ◽  
Alternating Electric Field ◽  
Graphene Nanoparticles ◽  
The Magnetic Field

Hybrid magnetorheological elastomers (hMREs) were manufactured based on silicone rubber, silicone oil, carbonyl iron microparticles, graphene nanoparticles and cotton fabric. Using the hMREs, flat capacitors (FCs) were made. Using the installation described in this paper, the electrical capacitance and the coefficient of dielectric losses of the hMREs were measured as a function of the intensity of the magnetic field superimposed over an alternating electric field. From the data obtained, the electrical conductivity, the relative dielectric permittivity and magnetodielectric effects are determined. It is observed that the obtained quantities are significantly influenced by the intensity of the magnetic field and the amount of graphene used.

scholarly journals Colossal Negative Magnetoresistance Effect in a La1.37Sr1.63Mn2O7 Single Crystal Grown by Laser-Diode-Heated Floating-Zone Technique

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 547
Author(s):  
Si Wu ◽  
Yinghao Zhu ◽  
Junchao Xia ◽  
Pengfei Zhou ◽  
Haiyong Ni ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Single Crystal ◽  
Laser Diode ◽  
Room Temperature ◽  
Floating Zone ◽  
Magnetoresistance Effect ◽  
X Ray ◽  
Mr Effect ◽  
Distinct Features ◽  
The Magnetic Field

We have grown La 1.37 Sr 1.63 Mn 2 O 7 single crystals with a laser-diode-heated floating-zone furnace and studied the crystallinity, structure, and magnetoresistance (MR) effect by in-house X-ray Laue diffraction, X-ray powder diffraction, and resistance measurements. The La 1.37 Sr 1.63 Mn 2 O 7 single crystal crystallizes into a tetragonal structure with space group I4/mmm at room temperature. At 0 T, the maximum resistance centers around ∼166.9 K. Below ∼35.8 K, it displays an insulating character with an increase in resistance upon cooling. An applied magnetic field of B = 7 T strongly suppresses the resistance indicative of a negative MR effect. The minimum MR value equals −91.23% at 7 T and 128.7 K. The magnetic-field-dependent resistance shows distinct features at 1.67, 140, and 322 K, from which we calculated the corresponding MR values. At 14 T and 140 K, the colossal negative MR value is down to −94.04(5)%. We schematically fit the MR values with different models for an ideal describing of the interesting features of the MR value versus B curves.

MRE Damping Characteristics Evaluation

2016 ◽  
Vol 699 ◽  
pp. 31-36 ◽  
Author(s):  
Eduard Chirila ◽  
Ionel Chirica ◽  
Doina Boazu ◽  
Elena Felicia Beznea
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Smart Materials ◽  
Magnetorheological Elastomers ◽  
Damping Characteristics ◽  
The Subject ◽  
Energy Absorbing ◽  
The Magnetic Field ◽  
Material Form

The paper addresses the study of the damping characteristics estimation and behaviour of the magnetorheological elastomers (MREs) in the absence of magnetic field. This type of material actively changes the size, internal structure and viscoelastic characteristics under the external influences. These particular composite materials whose characteristics can vary in the presence of a magnetic fields are known as smart materials. The feature which causes the variation of properties in magnetic fields is explained by the existence of polarized particles which change the material form by energy absorbing. Damping is a special characteristic that influences the vibratory of the mechanical system. As an effect of this property is the reducing of the vibration amplitudes by dissipating the energy stored during the vibratory moving. The main characteristic that is based on the determination of the damping coefficient is the energy loss, which is the subject of the present paper. Before to start the characteristics determination in the presence of the magnetic field, it is necessary to study these characteristics in the absence of magnetic field. The MRE specimens have been manufactured and tested under the light conditions (non magnetic field). A special experimental test rig was built to investigate the response of the MRE specimens under the charging force. The experimental results show that the loss energy of the MRE specimen can be determined from the charging-discharging curves versus displacement. The results of the MRE specimen are presented in this paper: MRE with feromagnetic particles not exposed in magnetic field during fabrication.

Numerical analysis and simulations of the magnetic field and hydrophobicity effect on the journal bearing dynamics

2016 ◽  
Vol 231 (5) ◽  
pp. 561-571 ◽  
Author(s):  
Simona Fialová ◽  
František Pochylý ◽  
Eduard Malenovský
Keyword(s):  
Magnetic Field ◽  
Mathematical Models ◽  
Reynolds Equation ◽  
Hydrophobic Surface ◽  
Hydrophilic Surface ◽  
Flowing Liquid ◽  
Stiffness And Damping ◽  
Bearing Dynamics ◽  
The Magnetic Field ◽  
Generalized Reynolds Equation

The article contains mathematical models of Reynolds equation with the effects of hydrophobicity of surface and magnetic field. The first section provides a new mathematical model of the solution of the generalized Reynolds equation and its application for a hydrophilic surface. It also derives a new boundary condition for the contact of a flowing liquid with a hydrophobic surface. This wettability condition is defined in dependence on the adhesion coefficient k. The second part presents mathematical models of Reynolds equation including the effect of hydrophobia and magnetic field. For all problems, the solutions are shown and the definitions of the stiffness and damping matrices of the liquid layer are outlined. From the results, it can be deduced that hydrophobic surface significantly affects the velocity profile of the liquid. It leads to a higher effect of the Lorentz force and thus of the magnetic field in comparison with a hydrophilic surface of the bearing lining.

Tuning Active Magnetorheological Elastomers for Damping Applications

2010 ◽  
Vol 636-637 ◽  
pp. 766-771 ◽  
Author(s):  
Anna Boczkowska ◽  
Stefan F. Awietjan
Keyword(s):  
Magnetic Field ◽  
Carbonyl Iron ◽  
Volume Fraction ◽  
Iron Particles ◽  
Magnetorheological Elastomers ◽  
Ferromagnetic Component ◽  
Electron And Light Microscopy ◽  
Tan Δ ◽  
Microscopy Techniques ◽  
The Magnetic Field

Magnetorheological elastomers (MREs) were obtained by mixing soft polyurethane and carbonyl-iron particles. The effect of the volume fraction of the ferromagnetic particles on the MREs microstructure and properties, as well as their arrangement in relation to the external magnetic field were investigated. As a ferromagnetic component carbonyl–iron powder, with particle size from 6-9µm, was used. The amount of the carbonyl iron particles was varied from 1.5 to 33.0 %(v/v). The samples were produced with randomly dispersed and aligned carbonyl iron particles. Scanning electron and light microscopy techniques were used for the MRE microstructure observations. The rheological properties (G’, G’’ and tan δ) of the MRE were tested without and with the application of the magnetic field. It was found that the microstructure of MREs, particularly the amount and arrangement of the carbonyl-iron particles, has a significant influence on their rheological and damping properties.

Viscoelastic Responses of Silicone-Rubber-Based Magnetorheological Elastomers Under Compressive and Shear Loadings

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Rui Li ◽  
L. Z. Sun
Keyword(s):  
Magnetic Field ◽  
Silicone Rubber ◽  
Viscoelastic Properties ◽  
Mechanical Performance ◽  
Dynamic Stiffness ◽  
Zero Magnetic Field ◽  
Dynamic Strain ◽  
Loading Frequency ◽  
Magnetorheological Elastomers ◽  
Mr Effect

Magnetorheological elastomers (MREs) are adaptive composite materials in the sense that their mechanical properties are tailored by the applied magnetic field. In this paper we developed both isotropic and anisotropic silicone-rubber-based MREs. We examined the zero-magnetic-field dynamic stiffness and damping along with the magnetic field induced changes (the magnetorheological (MR) effect) for the viscoelastic properties of the MREs by conducting both compression and shear investigations. While the anisotropic MREs exhibited substantial magnetic-field-dependent viscoelastic properties at a medium magnetic field, the isotropic ones showed a negligible MR effect. The magnetic filler structure and concentration, loading frequency, and dynamic strain amplitude were all confirmed to play significant roles in the dynamic mechanical performance of the MREs.

DOMAIN STRUCTURE AND MR EFFECT OF FERROFLUID EMULSION

2001 ◽  
Vol 15 (06n07) ◽  
pp. 859-863 ◽  
Author(s):  
CHIKARA OGAWA ◽  
YUICHI MASUBUCHI ◽  
JUN-ICHI TAKIMOTO ◽  
KIYOHITO KOYAMA
Keyword(s):  
Magnetic Field ◽  
Shear Flow ◽  
Domain Structure ◽  
Silicone Oil ◽  
Dielectric Constants ◽  
Immiscible Liquids ◽  
Water Based ◽  
Mr Effect ◽  
Er Fluids ◽  
The Magnetic Field

Blends of immiscible liquids with different dielectric constants and viscosities were known to show the ER effect due to the change of the domain structure by the electric field. In this paper, we report on our attempt to explore the possibility of the magnetic analog of these blend-type ER fluids. Water-based ferrofluid was blended with silicone oil with higher viscosity than the ferrofluid, in order to see whether the negative MR effect can be induced. The domain structure and the viscosity under the magnetic field and shear flow were studied. Growth of the droplet due to coalescence was observed under the field, which resulted in the gradual decrease of the shear viscosity.

INVESTIGATING THE TIME DEPENDENCE OF THE MR EFFECT

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4832-4840 ◽  
Author(s):  
FERNANDO D. GONCALVES ◽  
J. DAVID CARLSON
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Response Time ◽  
Time Dependence ◽  
Dwell Time ◽  
High Shear ◽  
Proposed Model ◽  
Mr Effect ◽  
The Magnetic Field ◽  
Field Strengths

Magnetorheological fluids are known to respond in a matter of milliseconds to the application of a magnetic field. To date, however, very little work has been done to study the time dependence of the MR response. The purpose of this study is to investigate the response time of the fluid. Experiments were conducted on a high shear rate rheometer capable of fluid speeds in excess of 35 m/s. With an MR valve length of 6.35 mm, the resulting dwell times were as low as 0.18 ms. For each of three magnetic field strengths, a reduction in yield stress is observed as dwell time decreases. A model is proposed to represent the time response of the fluid to the application of the magnetic field. The experimental data and the proposed model are used to identify the response time of the fluid for each field strength. Results indicate that as the magnetic field increases, the response time of the MR fluid decreases. For the range of magnetic field strengths considered in this study the response time of the fluid ranged from 0.24 ms to 0.19 ms.

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