Papers by Keyword: Magnetorheological Finishing (MRF)

Abstract: One fiber stain measure and control system has been designed to meet the problem that the magnitude and uniformity of the fiber strain directly determine the properties and longevity of the carbon fiber continuous sucker rod during the pultrusion process. In this system, there are 2 key technologies. The first one is the sensor that is used to measure the micro bend strain of the carbon fiber during the pultrusion process, designed base on fiber micro-bend principle, using silicon film as sensitive element and fabricated by silicon integrated circuit technology and three dimensional processes. Another is the executive unit of the system: Magneto-rheological Fluids torsional damper, which is designed base on one type of intelligent material named Magneto Rheological Fluids which can change its viscosity in millisecond according to the magnetic strength around it. So this paper provides a technical means to ensure the quality of the pultrusion process applied in fabricating the carbon fiber continuous sucker rod.

Abstract: Smart materials are being used in much larger scale in mechanical solutions. Aviation usage of these materials seems to be natural because of interest in new technologies use in this industry. In this article authors discuss characteristics of magnetoreological fluids as a smart materials, examples of its industrial usage, requirements on landing gear characteristics, design and lab tests of model shock absorber in which MRF was used as damping fluid.

Abstract: This paper presents experimental investigations of three MR fluid types under the influence of several factors in tension loading mode. One MR fluid was water-based, MRF-241ES, while the other two were both hydro-carbon based, MRF-132DG and MRF-122-2ED. The magnetic properties of the MR fluids varied significantly due to a higher particle density in the water-based MR fluid compared to the hydrocarbon-based MR fluids. Tension as a squeeze mode, is as an operational mode where two flat parallel surfaces, standing opposite to each other, are pulled apart from each other by an external force, acting along the path of the magnetic flux lines. The experiments were performed in a vertical direction in the environment of a DC magnetic field. Stress-strain curves of the MR fluids under tension showed similar characteristics despite the fact that different types of the carrier fluids were used. The results revealed that the magnitude of the stress, for a given strain value, depended on the applied current and the initial gap size. It was found that, for higher applied currents and smaller initial gap sizes, there were larger stress values. However, the tensile speed had no significant effect on the stress-strain curves of MR fluids.

Abstract: This paper brings forward a flexible fixture system based on magneto-rheological fluid. It is a holding and positioning device that has flexible surface of change rigidity by using current and magneto-rheological fluid valve to control variety of rigidity. It can adapt all kinds of rigidity and shape holding objects, the stress is adapted to object surface of any shape. Flexible fixture based on magneto-rheological fluid has simple structure and faster execution action and lower cost relative to pure mechanical control system. The simulation results are shown that the fixture system has better positioning precision and clamping effect. The fixture device can be applied in many domains.

Abstract: In this paper, based on the analysis of the damping torque of rotary disc-type magnetorheological fluid (MRF) damper, a new kind of MRF disc-type damper is proposed. The working disc of the new kind of damper has a wedged shape that results in variable working clearances, and hence a nonhomogeneous magnetic field is produced. The magnetic resistance of the MRF filled in the variable clearance is analyzed and the impact of the produced nonhomogeneous magnetic field on the damping torque of the damper is studied. Experiments are conducted and the damper performance under steady shear rate is evaluated with an author-designed test stand. The experimental results show that under the same exciting current and other conditions the output damping torque produced by the MRF of the new kind of damper is much greater than that of the ordinary dampers with parallel disc surfaces and constant working clearance.

Abstract: This paper presents ride comfort analysis of a full-vehicle featuring controllable magnetorheological (MR) shock absorbers. In order to achieve this goal, two flow mode MR shock absorbers (one for front suspension; one for rear suspension) are designed using an optimization methodology based on design specifications for a commercial passenger vehicle. The optimization problem is to find optimal geometric dimensions of the magnetic parts for the front and rear MR shock absorbers in order to improve the performance such as damping force. After manufacturing the proposed MR shock absorbers, their field-dependent damping forces are experimentally evaluated. The governing equation of motion for the full-vehicle is then established and integrated with the model of the MR shock absorbers. Subsequently, skyhook controllers for the MR suspensions are formulated and implemented. Ride comfort performances of the full-vehicle installed with the proposed MR shock absorbers are evaluated under bump and random road.

Abstract: Composition, synthesis and structural properties of ferrofluids and magnetorheological fluids are reviewed and compared. The similarities and main differences between the two types of magnetically controllable fluids are outlined and exemplified in the paper. Chemical synthesis and structural characterization of magnetizable fluids for engineering and biomedical applications are thoroughly discussed.

Abstract: In this paper, the behaviours of three types of MR fluids under quasi-static loadings in tension mode were investigated. One type of water-based and two types of hydrocarbon-based MR fluids were activated by a magnetic field generated by a coil using a constant value of DC electrical current. Experimental results in terms of stress-strain relationships showed that the MR fluids had distinct unique behaviours during the tension process. A high ratio of solid particles to carrier liquid in the MR fluid is an indication of high magnetic properties. The water-based MR fluid had a relatively large solid-to-liquid ratio. At a given applied current, a significant increase in tensile stress was obtained in this fluid type. On the other hand, the hydrocarbon-based MR fluids had relatively lower solid to liquid ratios, whereby, less increases in tensile stress were obtained. The behaviours of MR fluids were dependent on the relative movement between the solid magnetic particles and the carrier fluid. A complication occurs because, in the presence of a magnetic field, there will be a tendency of the carrier fluid to stick with the magnetic particle

Abstract: Large density of the dispersed phase in magnetorheological (MR) fluids has hindered operating MR test and their industrial application. This present work adopted Fe3O4 nanoparticles to prepare MR fluid because of their moderate density and good magnetic property. Furthermore, in order to resolve aggregation problem of Fe3O4 particles due to their nano-scaled size, conducting polypyrrole (PPY) was synthesized around naono-sized Fe3O4 particles via conventional oxidation polymerization. Weight ratio of PPY to Fe3O4 was adjusted to be 5% to avoid possible deterioration of the magnetic property of Fe3O4 particles. TEM images described the morphology for PPY-Fe3O4, and XRD pattern provided information on structural characterization and particle size. Finally, MR performances of pure Fe3O4 and PPY-Fe3O4 nanocomposites were investigated via rotational and oscillatory tests.

Abstract: This paper presents the development of a variable stiffness and damping isolator using magnetorheological (MR) fluid technology. The MR fluid isolator is composed of two variable volume rubber bladder filled with MR fluid, a pipe and a MR valve connecting them. One of the bladders supports disturbance force and the MR fluid flows between two bladders because of the variation of bladder volume due to deformation. The shear stress of the MR fluid in MR valve is varied by an applied magnetic field, which thereby varies the characteristics of the isolator, such as its stiffness and damping. A mathematical model of the isolator was derived, and a prototype of the MR fluid bladder spring was fabricated and its dynamic behavior was measured in vibration force for a wide range of frequencies under various applied magnetic fields. The parameters of the model under various magnetic fields were calculated and the bladder dynamic performances were evaluated. A non-resonant control was employed to minimize the vibration amplitude of the system. Numerical simulation results indicated that the semiactive control system produced much better isolation performance than a passive system.