Synthesis and Characterization of Antifriction Magnetorheological Fluids for Brake

Magnetorheological (MR) fluids are smart materials with shear strength ranging between zero to 100 kPa under the influence of magnetic field. The present paper discusses the synthesis of MR fluid and its application in brake. In MR brake, gap between stator and rotor is filled with low (off-state) viscosity MR fluid. On the application of magnetic field, MR fluid changes its state from liquid to semi-solid by aligning magnetic particles in chains. Due to such chaining action, yield strength of fluid increases, friction between stator and rotor increases and fulfils the braking function. The strength of magnetic particle is a function of relative speed between stator and rotor, applied magnetic field, and volume percentage of magnetic particle. In this study antifriction (off-state) and strong chain (on-state) CI based MR fluid has been prepared by mixing oleic acid as antifriction additives and tetramethylammonium hydroxide as surfactant to reduce the agglomeration of the MR fluid. Yield strengths of the synthesized MR fluid in on-state and off-state have been compared with commercially available MRF 241ES fluid. A flywheel based MR brake experimental setup has been developed to analyze the performance of designed and developed MR brake.Results show that synthesized MR fluid is stronger and faster in response compared to MRF 241ES fluid.Defence Science Journal, 2013, 63(4), pp.408-412, DOI:http://dx.doi.org/10.14429/dsj.63.263

Synthesis and Characterisation of Nano Silver Particle-based Magnetorheological Fluids for Brakes

Magnetorheological (MR) fluids can be used as brake friction materials subject to heat transfer properties of the fluids to dissipate the heat generated during braking action. The aim of this manuscript is to synthesise MR fluids having higher heat transfer properties than that of the conventional MR fluid. The coating of nano-silver-particles, having thermal conductivity more than five-times than that of iron particles used in the MR fluids, has been tried to enhance the heat dissipation rate of MR fluids. To perform feasibility study on usage of silver particles, three composition of MR fluids (without any silver particles, with 0.25 per cent weight and 0.50 per cent weight silver particles) were synthesised. The scanning electron microscopic photographs and EDX analysis of the iron particles have been presented. Shear strengths of all three different compositions of MR fluids were measured using magnetorheometer and the results have been plotted. The effect of silver particles on shear stress of MR fluids has been described. A flywheel-based MR brake experimental setup was developed to analyse the performance of synthesised MR fluids. ‘T’ type thermocouples were used to avail the temperature distribution of the fabricated MR brake. The results of temperature distribution of brakes containing three different compositions of MR fluids have been presented and compared

Development of Analytical Equations for Design and Optimization of Axially Polarized Radial Passive Magnetic Bearing

In the present research work, analytical equations have been developed for design and optimization of radial axial polarized passive magnetic bearing (PMB) with single layer for facilitating easy and quick solution, obviating the need of costly software. Seven design variables: eccentricity, rotor width, stator width, rotor length, stator length, clearance, and mean radius were identified as the main factors affecting the design and were thus considered in the development of analytical equations. The results obtained from the developed analytical equations have been validated with the published results. The optimization of the bearing design, with minimization of magnet volume as the objective function, was carried out to demonstrate the accuracy and usefulness of the developed equations

Synthesis and Characterization of Nano-Particles Based Magnetorheological Fluids for Brake

Magnetorheological (MR) fluids, to be used as brake friction materials, must have high heat transfer rate to dissipate the heat generated during the braking action. The aim of this manuscript is to synthesize MR fluids with nano-silver and nano-copper particles to increase the heat transfer rate and characterize the demagnetizing effect of those particles on the shear stress of MR fluids. Five different MR fluids, containing a different percentage of silver and copper nano particles, were synthesized. Shear stresses of all five MR fluids were measured using magnetorheometer and the results have been plotted. A flywheel based MR brake experimental setup was developed to analyze the performance of synthesized MR fluids. “T” type thermocouples were used to measure the temperature distribution of the fabricated MR brake. The results of the temperature distribution of brakes containing five synthesized MR fluids have been presented and compared

Particle Dynamics of Polydisperse Magnetorheological Fluids

In the present research work, three dimensional simulations of magnetorheological fluids, containing soft magnetic polydisperse particles in silicone oil, has been presented. The computer simulation helps to visualize and analyze the formed transient microstructures. The initial positions of particle-centres were decided based on random distribution. The particle positions were updated considering magnetic, hydrodynamic and repulsions forces on each particle along with explicit time marching scheme. Finally the particle’s positions at 10 ms have been plotted. The yield behaviors of MRFXXS (small sized: 2 to 33 µm) and MRFXXL (large sized: 45 to 212 µm) have been estimated using particle dynamic simulations and the predicted results have been compared with the results obtained from experiments. Due to large number of particles and limitations of computer hardware, the yield behavior of MRFXXM1 i.e. mixed (2 to 212 µm) sized magnetic particles could not be simulated. However, experiments were performed to investigate the yield behavior of MRFXXM1. The results show that MRFXXM1 is better than MRFXXS and MRFXXL

Synthesis and Characterisation of Nano Silver Particle-based Magnetorheological Fluids for Brakes

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