LINEAR VISCOELASTICITY OF MR FLUIDS: DEPENDENCE ON MAGNETIC FIELDS

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1198-1204 ◽  
Author(s):  
W. H. LI ◽  
P. Q. ZHANG ◽  
X. L. GONG ◽  
P. B. KOSASIH
Keyword(s):  
Magnetic Field ◽  
Viscoelastic Properties ◽  
Parallel Plate ◽  
Dynamic Properties ◽  
Mr Fluids ◽  
Good Accord ◽  
Stable Clusters ◽  
Linear Viscoelastic ◽  
Reduced Iron Powder ◽  
Plate Geometry

The paper presents investigation of dynamic properties of MR fluids by using a rheometer with parallel-plate geometry. The sample is reduced iron powder based MR suspensions. Linear viscoelastic properties of such sample, which can be variably controlled using a magnetic field, are obtained and summarized based on oscillatory tests. Four field-induced regimes, I, II, III, and IV, are found in the system, which are defined by three critical field strengths: BC1< BC2< BC3. MR fluids in regime I through IV experience four typical structural convolutions: coexisting of particles and random chains; coexisting of chains and random clusters; coexisting of clusters and chains; stable clusters. Such results are in good accord with experimental results achieved by Liu's group using light scattering techniques.

TEMPERATURE DEPENDENCE OF MR FLUIDS

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2725-2731 ◽  
Author(s):  
W. H. LI ◽  
G. CHEN ◽  
S. H. YEO ◽  
H. DU
Keyword(s):  
Temperature Dependence ◽  
Viscoelastic Properties ◽  
Parallel Plate ◽  
Oscillatory Shear ◽  
Steady Shear ◽  
Frequency Sweep ◽  
Mr Fluid ◽  
Mr Fluids ◽  
Nonlinear Viscoelastic ◽  
Linear Viscoelastic

The rheological properties of MR fluids, MRF-132LD, are investigated under the steady shear and oscillatory shear for a range of operating temperatures from 20°C to 60°C. This was accomplished by using an advanced rheometer with the parallel-plate configuration. Under the steady shear, the Herschel–Bulkley model is used to model the rheology of the MR fluid. The corresponding parameters namely, τyd, K and n were determined at various temperatures, in an attempt to minimize the discrepancies between the experimental results and that predicted by the model. The results show that τyd, K and n all show decreasing trend with temperature. The results suggest that the MR fluid get "thinner" with increasing temperatures. Under the oscillatory shear, viscoelastic properties of the MR fluid were studied in the frequency sweep mode. The storage modulus, G′, decreases with increasing temperatures in both the linear viscoelastic region and the nonlinear viscoelastic region. In addition, two critical frequencies, ωcr and ωm, were identified in the latter region. They were found to decrease with increasing temperatures. Finally, thermodynamics are used to explain temperature dependence of MR properties.

Experimental Investigation of the Transient Behavior of MR Fluids

2011 ◽  
Author(s):  
Ju¨rgen Maas ◽  
Dirk Gu¨th
Keyword(s):  
Magnetic Field ◽  
Experimental Investigation ◽  
Response Time ◽  
Dynamic Properties ◽  
Transient Behavior ◽  
Current Control ◽  
Large Signal ◽  
Carrier Fluid ◽  
Mr Fluids ◽  
The Magnetic Field

The transient behavior of MRF actuators is an important property for certain applications that is mainly affected by three delays, occurring from the dynamic properties of the coil current, the magnetic field and the torque generation by the MRF. In order to investigate the transient behavior of the generated torque with respect to the magnetic field, which is mainly affected by the motion of the MR particles in the carrier fluid, the mentioned response time of the electrical and magnetic domains must be in an appropriated ratio in comparison to the MRF response time to obtain reliable results by experiments. Therefore a special disc-type test actuator with outstanding dynamics is designed that minimizes the delays by the use of an ultrafast current control and a magnetic core made of soft ferrite material for preventing the effects of eddy currents. For the experimental investigation of the transient behavior of MR fluids, the small signal as well as the large signal behavior is analyzed for different test signals and load conditions of the actuator. Various results of the investigated transient behavior are shown finally for two different MR fluids featuring response times of about 1 ms for the fluid itself and switching times of about 4 ms for the MRF actuator.

Magnetorheological Characterization of Polymer-Iron Composite Suspensions

2004 ◽  
Vol 449-452 ◽  
pp. 1201-1204 ◽  
Author(s):  
Min Seong Cho ◽  
Hyoung Jin Choi
Keyword(s):  
Magnetic Field ◽  
Parallel Plate ◽  
Suspension Polymerization ◽  
Measuring System ◽  
Composite Particles ◽  
Dispersed Phase ◽  
Mr Fluids ◽  
Polymerization Method ◽  
Mr Characteristics

Composite particles (CIPMMA) of carbonyl iron (CI) and poly (methyl methacrylate) (PMMA) were prepared by a suspension polymerization method using CI dispersions in MMA monomer, and these were adopted as dispersed phase of magnetorheological (MR) fluids. The CIPMMA can resolve several problems of MR fluids having CI alone such as severe sedimentation and poor dispersion stability. Flow and viscelastic properties of the MR fluids were analyzed via a rotational rheometer equipped with a magnetic field supplier using measuring system of a parallel plate. The MR characteristics like yield stress were affected by the CI contents in the composite particles.

MAGNETORHEOLOGY OF CARBONYL-IRON SUSPENSION WITH IRON/MCM-41 ADDITIVE

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4981-4987 ◽  
Author(s):  
F. F. FANG ◽  
B. J. PARK ◽  
H. J. CHOI ◽  
W. S. AHN
Keyword(s):  
Magnetic Field ◽  
Carbonyl Iron ◽  
Parallel Plate ◽  
Mr Fluid ◽  
Flow Response ◽  
Plate Geometry ◽  
Mesoporous Particles ◽  
Oscillation Characteristics ◽  
Mesoporous Silica Particle ◽  
Mcm 41

Iron containg hexagonal mesoporous silica particle ( Fe - MCM -41) was prepared and adopted into carbonyl-iron ( CI ) based magnetorheological (MR) suspension as an additive to improve the sedimentation problem of the CI based MR fluid. Structural properties and morphology of the synthesized Fe - MCM -41 particles were observed using SEM. Their MR properties such as oscillation characteristics and flow response (shear stress and shear viscosity) were examined via a rotational rheometer in parallel plate geometry equipped with a magnetic field supplier under external magnetic field strengths ranging from 0 to 257 kA/m. The addition of Fe -containing mesoporous particles into CI suspension was found to improve not only MR behaviors but also sedimentation problem of the CI based MR fluid.

Development of a Sliding Plate Rheometer to Measure the High Frequency Viscoelastic Properties of Polymer Melts

2007 ◽  
Vol 17 (6) ◽  
pp. 62563-1-62563-8
Author(s):  
Chelsea A. Braybrook ◽  
Jennifer A. Lee ◽  
Philip J. Bates ◽  
Marianna Kontopoulou
Keyword(s):  
Rheological Properties ◽  
High Frequency ◽  
Viscoelastic Properties ◽  
Parallel Plate ◽  
Polymer Melts ◽  
Measured Data ◽  
Rheological Models ◽  
Linear Viscoelastic ◽  
Good Agreement ◽  
Sliding Plate

Abstract A newly designed and constructed sliding plate rheometer is used to measure the high frequency (210 Hz) linear viscoelastic properties of two model polymers: polybutene (PB) and polydimethylsiloxane (PDMS). Using well-known rheological models, extrapolations of the viscoelastic measurements obtained on a rotational parallel plate rheometer to a frequency of 210 Hz are used to assess the performance of the high frequency sliding plate rheometer. Good agreement between the extrapolated and measured data demonstrates the ability of the sliding plate rheometer to measure the high frequency rheological properties of both Newtonian and shear-thinning materials.

LINEAR/NONLINEAR MECHANICAL PROPERTIES OF ELECTRORHEOLOGICAL MATERIALS

1992 ◽  
Vol 06 (15n16) ◽  
pp. 2595-2607 ◽  
Author(s):  
DANIEL R. GAMOTA ◽  
FRANK E. FILISKO
Keyword(s):  
Viscoelastic Properties ◽  
Small Amplitude ◽  
Dynamic Properties ◽  
Flow Conditions ◽  
Nonlinear Viscoelastic ◽  
Nonlinear Mechanical ◽  
Linear Viscoelastic ◽  
Nonlinear Dynamic Properties ◽  
Strain Frequency ◽  
Constant Shear Rate

The stress response of an electrorheological (ER) material is modified by the application of an electric field. Various studies have shown that the ER material can behave as a linear viscous, linear viscoelastic, nonlinear viscoelastic, plastic, or viscoelastic-plastic body. Furthermore, several different experimental techniques are conducted to observe the ER material's behavior as a function of strain, strain frequency, field strength, and ER material concentration. Small amplitude dynamic studies are used to observe the ER material's linear viscoelastic properties, while moderate and large amplitude studies are used to observe the material's fundamental nonlinear dynamic properties. Finally, constant shear rate experiments are performed to observe the apparent viscosity of the ER material during flow conditions.

RHEOLOGICAL PROPERTIES OF NOVEL MAGNETORHEOLOGICAL FLUIDS

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4849-4857 ◽  
Author(s):  
S. MANTRIPRAGADA ◽  
X. WANG ◽  
F. GORDANINEJAD ◽  
B. HU ◽  
A. FUCHS
Keyword(s):  
Magnetic Field ◽  
Rheological Properties ◽  
Yield Stress ◽  
Parallel Plate ◽  
Magnetorheological Fluids ◽  
High Yield ◽  
Iron Particles ◽  
Shear Rates ◽  
Low Viscosity ◽  
Mr Fluids

The rheological properties of novel MR fluids are characterized using a parallel plate MR shear rheometer. In these MR fluids the surface of iron particles is coated with a polymer. The rheological properties are measured and compared at various magnetic field strengths, shear rates and strain amplitudes. It has been shown that these MR fluids exhibit stable and desirable rheological properties such as, low viscosity and high yield stress.

scholarly journals Magnetic Janssen effect

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
L. Thorens ◽  
K. J. Måløy ◽  
M. Bourgoin ◽  
S. Santucci
Keyword(s):  
Magnetic Field ◽  
Dynamic Properties ◽  
Radial Force ◽  
Fine Tuning ◽  
Apparent Mass ◽  
Confined Geometries ◽  
Pairwise Interactions ◽  
Janssen Effect ◽  
Lateral Walls ◽  
Granular Column

AbstractA pile of grains, even when at rest in a silo, can display fascinating properties. One of the most celebrated is the Janssen effect, named after the pioneering engineer who explained the pressure saturation at the bottom of a container filled with corn. This surprising behavior arises because of frictional interactions between the grains through a disordered network of contacts, and the vessel lateral walls, which partially support the weight of the column, decreasing its apparent mass. Here, we demonstrate control over frictional interactions using ferromagnetic grains and an external magnetic field. We show that the anisotropic pairwise interactions between magnetized grains result in a radial force along the walls, whose amplitude and direction is fully determined by the applied magnetic field. Such magnetic Janssen effect allows for the fine tuning of the granular column apparent mass. Our findings pave the way towards the design of functional jammed materials in confined geometries, via a further control of both their static and dynamic properties.

Preparation, Characterization and Processing of PCL/PHO Blends by 3D Bioplotting

2020 ◽  
Vol 35 (5) ◽  
pp. 458-470
Author(s):  
S. Gopi ◽  
B. A. Ramsay ◽  
J. A. Ramsay ◽  
M. Kontopoulou
Keyword(s):  
Viscoelastic Properties ◽  
Biomedical Applications ◽  
Synergistic Effects ◽  
Thermal And Mechanical Properties ◽  
Flow Properties ◽  
Immiscible Blends ◽  
Melt Compounding ◽  
Linear Viscoelastic ◽  
Matrix Morphology ◽  
Good Flow

Abstract Blends of polycaprolactone (PCL) and poly(3-hydroxyoctanoate) P(3HO) were prepared by melt compounding. These immiscible blends exhibited droplet-matrix morphology at compositions up to 30 wt% P(3HO). Even though the addition of amorphous P(3HO) decreased the crystallinity of PCL, the crystallization temperature of the blends increased by 6 to 7 8C. Blends containing up to 30 wt% P(3HO) had higher crystallization rates, and lower crystallization half-times compared to neat PCL. The viscosity of PCL decreased upon addition of P(3HO), making the blends suitable for processing using a 3D bioplotter. Compositions with 10 to 30 wt% P(3HO) were ideal for processing, because of their improved crystallization kinetics, reduced stickiness and good flow properties. Estimation of the interfacial tension by fitting the Palierne model to the linear viscoelastic properties of the blends revealed good compatibility, which gave rise to synergistic effects in the thermal and mechanical properties. The fibres prepared by 3D bioplotting maintained droplet matrix morphology, with finer particle size than the original compounded material. In addition to favourable viscosity and thermal properties, the extruded fibres containing 30 wt% P(3HO) had comparable modulus to the neat PCL, while exhibiting good ductility. These blends may be suitable alternatives to PCL for biomedical applications, because they provide a range of crystallinities, crystallization rates and viscosities.

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