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.

On the properties of magnetorheological elastomers in shear mode: Design, fabrication and characterization

Abstract: Magnetorheological elastomers (MREs) are novel class of magneto-active materials comprised of micron-sized ferromagnetic particles impregnated into an elastomeric matrix, which exhibit variable stiffness and damping properties in a reversible manner under the application of an external magnetic field. Characterization of highly complex behavior of these active composites is a fundamental necessity to design adaptive devices based on the MREs. This study is mainly concerned with in-depth experimental characterizations of static and dynamic properties of different types of MREs using methods defined in related standards. For this purpose, six different types of MRE samples with varying contents of rubber matrix and ferromagnetic particles were fabricated. The static characteristics of the samples were experimentally evaluated in shear mode as a function of the magnetic flux density. The particular MRE sample with highest iron particles content (40% volume fraction) was chosen for subsequent dynamic characterizations under broad ranges shear strain amplitude (2.5–20%), excitation frequency (0.1–50 Hz) and applied magnetic flux densities (0–450 mT). The results revealed nearly 1672% increase in the MRE storage modulus under the application of a magnetic flux of 450 mT, which confirms the potential of the novel fabricated MRE for control of vibration and noise in various engineering applications.

Passive magnetorheological fluid device with excursion dependent characteristic

Abstract: A magnetorheological fluid device which exhibits excursion (stroke or rotation) dependent resistance (force or torque) which is obtained passively. Linear and rotary embodiments are described. The devices described herein include various ways for passively varying magnetic circuit reluctance to accomplish the stroke or rotation dependent characteristic. The devices include a first component with an internal cavity, a second component received in the cavity and moveable relative to the first component, a working zone created between the first and second component, a magnetorheological fluid contained therein, at least one permanent magnet for producing a magnetic field, a magnetic circuit for directing a magnetic flux created by the permanent magnet toward the magnetorheological fluid in the working zone, and passively varying a magnetic circuit reluctance (such as by changing a thickness of a magnetic return, by changing a gap thickness, by changing the material reluctance, by interacting multiple magnetic fields, or combinations thereof) as a function of excursion. This changes the magnetic field strength acting upon the MR fluid in the working zone and produces a force/torque which varies as a function of excursion (x or θ).

Dynamics of Self-Assembled Chaining in Magnetorheological Fluids

Abstract: The aggregation dynamics of paramagnetic spherical particles embedded in a viscous fluid is investigated via numerical simulations using a fully coupled three-dimensional model. Particles experience simultaneously Brownian motion, dipolar magnetic attraction, and multibody hydrodynamic interactions. When the dipole strength characterizing the ratio of magnetic attraction to random diffusion exceeds a critical value, particles join together forming supraparticle structures. As time evolves, particle/chain and chain/ chain interactions lead to a continuous increase of the cluster size. The mean length of particle chains has a power-law dependence with respect to time, as predicted by the theory of diffusion-limited aggregation. Both the exponent and the characteristic time scale agree very well with the experimental results of Promislow et al. (J. Chem. Phys. 1995, 102, 5492).

MR fluid sponge devices and their use in vibration control of washing machines

Abstract: High-strength, stable, magnetorheological (MR) fluids and devices such as rotary brakes and linear vibration dampers that enable the benefits of controllable fluid technology are now commercially available. Recently, a new way of using MR fluids in which the fluid is contained in an absorbent matrix has been developed. Such MR fluid sponge devices enable the benefits of controllable MR fluids to be realized in cost sensitive applications. Most of the high-cost components normally associated with a fluid-filled device can be eliminated with this approach. Low-cost, controllable MR sponge dampers are particularly appropriate for moderate-force vibration control problems where a high degree of control authority is desired. One attractive area for their application is in next-generation high-performance home washing machines. These new machines operate under varying agitation rates, load imbalances, and often at very high speeds, and as such require varying damping charateristics. Test results have shown the MR sponge damper to be an ideal way to control vibration in these new washing machines.