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.

Image analysis of the microstructure of magnetorheological elastomers

Abstract: The results presented refer to the structure analysis of magnetorheological elastomers (MREs), based on ferromagnetic particles in a polyurethane matrix. The influence of the volume fraction of the ferromagnetic particles on their arrangement in relation to the external magnetic field was investigated. The amount of carbonyl iron particles, of the average size 6–9 μm, varied from 1.5 to 33 vol.%. Scanning electron microscopy was used to observe magnetorheological elastomer microstructures. Image analysis has been applied to describe the microstructures. From author’s previous studies it is known that the microstructure anisotropy has significant effect on the properties of magnetorheological elastomers. Two different techniques of image analysis: skeleton by influence zone method and linear covariance function were used to reveal the anisotropy in particle arrangements. These methods allowed quantitative microstructure description. The results show that particle arrangement changes with their volume fraction. The analyses confirm particle chain networks in composites with higher iron content. Differences in particles arrangement for samples prepared under diverse conditions were also clearly shown.

Effects of polyvinylpyrrolidone and carbon nanotubes on magnetorheological properties of iron‐based magnetorheological fluids

Abstract: Magnetorheological (MR) fluids based on glycol, iron powder, polyvinylpyrrolidone (PVP), and carbon nanotubes (CNTs) were prepared. Effects of polyvinylpyrrolidone and carbon nanotubes on sedimentation stability and magnetorheological properties were studied. It is found that the synergetic effects of PVP and CNTs improve the sedimentation stability significantly, and the addition of CNTs reduces the sedimentation velocity and increases the equilibrium sedimentation ratio of the magnetizable particles in MR fluids remarkably. The addition of PVP can reduce the sedimentation velocity of the magnetizable particles, but cannot increase the equilibrium sedimentation ratio and will not change the up trend of apparent viscosity with the increasing intensity of the external magnetic field. When the PVP content is lower, the increment of original apparent viscosity of the MR fluids at zero-intensity of magnetic field is inconspicuous, and their values of apparent viscosity under magnetic field are similar. However, the apparent viscosity of the MR fluids increases tremendously when the contents of PVP increase to certain degree. The results show that the synergetic effects of PVP and CNTs not only improve the sedimentation stability of the MR fluid but also promote its magnetorheological effect. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1653–1657, 2006

System for abrasive jet shaping and polishing of a surface using magnetorheological fluid

Abstract: A fluid (40) having magnetorheological (MR) properties and including a finely-divided abrasive material is directed through a non-ferromagnetic nozzle (30) disposed axially of the helical windings of an electric solenoid (28). A magnetic field created by the solenoid orients and aligns the magnetic moments of the particles to form fibrils thereby stiffening the flowing MR fluid (40) which, when ejected from the nozzle (30), defines a highly collimated jet. Collimation of the MR material persists for a significant time outside the magnetic field, permitting use of the abrasive jet to shape and/or polish the surface of a workpiece (12) at some distance from the nozzle (30). The jet (35) is directed into a shroud (20) against a workpiece (12) mounted for multiple-axis rotation and displacement to meet predetermined material removal needs for shaping.