Topic
Magnetorheological fluid
About: Magnetorheological fluid is a research topic. Over the lifetime, 8538 publications have been published within this topic receiving 131502 citations. The topic is also known as: MRF & MR fluid.
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TL;DR: In this paper, an optimised design of a high-efficiency magnetorheological (MR) valve using finite element analysis is presented, which is composed of a core, a wound coil, and a cylinder-shaped flux return.
Abstract: This paper presents an optimised design of a high-efficiency magnetorheological (MR) valve using finite element analysis. The MR valve is composed of a core, a wound coil, and a cylinder-shaped flux return. The core and flux return form the annulus through which the MR fluid flows. The effects of magnetic field formation mechanism and MR effect formation mechanism on the MR valve performance are investigated. Analytical results of the magnetic flux density in the valve indicate that the saturation in the magnetic flux may be in the core, the flux return, or the valve length. To prevent the saturation as well as to minimise the valve weight, the dimensions of the valve are optimally determined using finite element analysis. In addition, this analysis is coupled with the typical Bingham plastic analysis to predict the MR valve performance.
88 citations
TL;DR: In this paper, the rheological response of highly swollen physical gels obtained by selfassembling of triblock copolymers containing low remanence ferromagnetic particles was investigated in the presence of external homogeneous magnetic fields.
Abstract: The rheological response of highly swollen physical gels obtained by self-assembling of triblock copolymers containing low remanence ferromagnetic particles was investigated in the presence of external homogeneous magnetic fields. Three different types of sample geometries with distinctive magnetic particle orderings were investigated: isotropic (no magnetic field present during synthesis), parallel to the plane of the gel film and perpendicular to the plane of the gel film. Both the storage and loss moduli exhibit a strong increase with magnetic field strength for all geometries. Dependence of the rheological response on particle volume fraction was also investigated. The strength of such rheological hardening, as well as its saturation behaviour, depend strongly on the relative orientation between particle strings, shear and external field. In some cases a very strong relative increase of storage modulus, up to 6000% was obtained. Further transient rheological studies suggest that strong rearrangement of the particle network is largely responsible for the enormous increase in elastic modulus. Parallel to that, a maximum in the loss factor was observed as a function of particle volume fraction and field strength and it was interpreted in terms of a competition between an increase in string (clusters) hardening and a decrease in their ability to deform and flow. These results suggest that magnetorheological gels are an intermediate system between magnetorheological elastomers (MREs) and magnetorheological fluids (MRFs) with directional dependent rheological response and partial rearrangement of the particle network.
88 citations
TL;DR: The evidence that the magnetic particles embedded in the gel were aligned in the direction of magnetic fields, accompanied by stretching of the gel network concludes that the giant magnetoelastic phenomenon originates from the chain structure consisting of magnetic particles similar to magnetic fluids.
Abstract: A new class of magnetoelastic gel that demonstrates drastic and reversible changes in storage modulus without using strong magnetic fields was obtained. The magnetic gel consists of carrageenan and carbonyl iron particles. The magnetic gel with a volume fraction of magnetic particles of 0.30 exhibited a reversible increase by a factor of 1400 of the storage modulus upon a magnetic field of 500 mT, which is the highest value in the past for magnetorheological soft materials. It is considered that the giant magnetoelastic behavior is caused by both high dispersibility and high mobility of magnetic particles in the carrageenan gel. The off-field storage modulus of the magnetic gel at volume fractions below 0.30 obeyed the Krieger–Dougherty equation, indicating random dispersion of magnetic particles. At 500 mT, the storage modulus was higher than 4.0 MPa, which is equal to that of magnetic fluids, indicating that the magnetic particles move and form a chain structure by magnetic fields. Morphological study r...
88 citations
TL;DR: In this article, various electrolytic and carbonyl iron powder based MR fluids have been synthesized by mixing grease as a stabilizer, oleic acid as an antifriction additive and gaur gum powder as a surface coating to reduce agglomeration of the MR fluid.
88 citations
15 Sep 2000-Jsme International Journal Series C-mechanical Systems Machine Elements and Manufacturing
TL;DR: A base isolation system using "smart" dampers that can adapt to, and protect against, seismic excitatiorn of different characteristics that is shown to be a most effective alternative for a broad class of earthquakes including near-source events.
Abstract: Consideration of near-source, high velocity, long-period seismic pulses, as were recorded during the Northridge and Kobe earthquakes, has taught engineers and researchers that ground motions due to such earthquakes can be difficult to accommodate. This paper discusses a base isolation system using "smart" dampers, such as magnetorheological fluid dampers, that can adapt to, and protect against, seismic excitatiorn of different characteristics. A linear, two degree-of-freedom, lumped-mass model of a base-isolated budding is used as the testbed for this study. Linear viscous dampers are shown to have an optimal damping level for several design earthquakes to achieve minimum peak accelerations. A study of a family of controllers for the smart damper is used to find an "optimal" isolation system over the suite of ground motions considered. This "optimal" system further decreases the base drift compared to the "optimal" linear viscous damper without increasing the accelerations imparted into the superstructure. The "smart" damper is shown to be a most effective alternative for a broad class of earthquakes including near-source events.
88 citations