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.

Statistical analysis of magnetically soft particles in magnetorheological elastomers

Abstract: The physical properties of magnetorheological elastomers (MRE) are a complex issue and can be influenced and controlled in many ways, e.g. by applying a magnetic field, by external mechanical stimuli, or by an electric potential. In general, the response of MRE materials to these stimuli is crucially dependent on the distribution of the magnetic particles inside the elastomer. Specific knowledge of the interactions between particles or particle clusters is of high relevance for understanding the macroscopic rheological properties and provides an important input for theoretical calculations. In order to gain a better insight into the correlation between the macroscopic effects and microstructure and to generate a database for theoretical analysis, x-ray micro-computed tomography (X-μCT) investigations as a base for a statistical analysis of the particle configurations were carried out. Different MREs with quantities of 2–15 wt% (0.27–2.3 vol%) of iron powder and different allocations of the particles inside the matrix were prepared. The X-μCT results were edited by an image processing software regarding the geometrical properties of the particles with and without the influence of an external magnetic field. Pair correlation functions for the positions of the particles inside the elastomer were calculated to statistically characterize the distributions of the particles in the samples.

Principle, design and modeling of an integrated relative displacement self-sensing magnetorheological damper based on electromagnetic induction

Abstract: In order to make full use of the controllable damping characteristics of magnetorheological (MR) dampers, feedback control of the damping forces for MR dampers is necessary, which needs extra dynamic response sensors and control systems as active control systems do. The extra dynamic response sensors for semi-active control of the MR dampers will increase the application cost of MR dampers, occupy the installation space, complicate the system, and decrease the reliability. In this paper, an integrated relative displacement sensor (IRDS) technology to make MR dampers self-sensing based on electromagnetic induction, and the principle of an integrated relative displacement self-sensing MR damper (IRDSMRD) based on the IRDS technology, are introduced. The IRDSMRD mainly comprises an exciting coil wound on the piston and an induction coil wound on the nonmagnetic cylinder. In the IRDSMRD, the coil wound on the piston simultaneously acts as the exciting coils of the MR fluid and the IRDS while the coil wound on the cylinder acts as the induction coil of the IRDS. The MR fluid in the annular fluid channel and the IRDS are simultaneously energized by the exciting coil through letting the carrier of the IRDS (AC) possess different frequency from the current for the MR fluid (DC), which realizes the frequency division multiplexing of the exciting coil. Based on the proposed principle for the IRDS and IRDSMRD, an IRDSMRD is designed and modeled and the damping and sensing performances of the designed and developed IRDSMRD are also modeled and analyzed using the finite element method (FEM) with the software package Maxwell 2D. The research results indicate that the function of the relative displacement sensing property can be integrated into MR dampers, and the designed IRDSMRD possesses large controllable damping ratio and good relative displacement sensing performance utilizing the IRDS technology proposed in this paper.

The strengthening effect of guar gum on the yield stress of magnetorheological fluid

Abstract: In this paper we present a novel approach for producing obvious strengthening of the magnetorheological (MR) effect of MR fluids. Carbonyl iron powders coated with guar gum were used as magnetic particles in the MR fluid. Experimental results showed that inducing a guar gum coating not only greatly improved the sedimentation stability but also strengthened the yield stress of the MR fluid. An intermolecular force based model was proposed for explaining the strengthening effect.

Magnetorheological fluid composites synthesized for helicopter landing gear applications

Abstract: Magnetorheological fluid composites were formulated in this study to investigate their performance for potential use in landing gear hydraulic systems, such as shock struts. The magnetorheological fluids synthesized here utilized three hydraulic oils certified for use in landing gear, two average diameters of spherical magnetic particles, and a lecithin surfactant. The magnetorheology of these fluids was characterized, including (a) magnetorheology (yield stress and viscosity) as a function of magnetic field, (b) sedimentation analysis using an inductance-based sensor, (c) cycling of a small-scale magnetorheological damper undergoing sinusoidal excitations at frequencies of 2.5 and 5 Hz, and (d) impact testing of an magnetorheological damper for a range of magnetic field strengths and velocities using a free-flight drop tower facility. The goal of this research is to analyze the performance of these magnetorheological fluid composites, compare their behavior to standard commercial magnetorheological fluid...

The effect of silane coupling agent on the dynamic mechanical properties of iron sand/ natural rubber magnetorheological elastomers

Abstract: Isotropic and anisotropic magnetorheological elastomers (MREs) containing unmodified and silane modified iron sand particles in a natural rubber matrix were prepared. Tan δ and the amount of energy dissipated during cyclic deformation were used as the parameters to assess damping. Tan δ was measured through dynamic mechanical analysis over a range of frequency (0.01–130 Hz), strain amplitude (0.1–4.5%) and temperature (−100–50 °C). Energy dissipated was measured using a universal tester under cyclic tensile loading. The silane coupled improved the amount of energy dissipated during hysteresis tests as well as tan δ over the range of frequency and strain amplitude explored and tan δ increased with increasing magnetic field up to a saturation point at 600 mT. However, the presence of coupling agent and formation of different lengths of aligned particles did not strongly affect the value of Tg and maximum tan δ at Tg. Evidence from scanning electron microscopy (SEM) supported that the use of modified iron sand does not interfere with the formation of magnetic particles chains in the matrix during curing and the chains became longer and more aligned as the magnetic field strength increased.