Synthesis and Characterization of Magnetorheological (MR) Fluid for Different Engineering Applications

Abstract

Magnetorheological fluid (MRF) are suspensions of iron particles in a carrier oil. They are controllable smart fluid whose rheological properties change under the application of magnetic field. The design of Magnetorheological (MR) device and the composition of MR fluid used in it have a significant effect on its performance. In this study, MRF composition suitable for MR damper, MR brake and MR beam were determined based on optimization. Initially, the key ingredient of MRF, that is, iron particles of different average sizes, were characterized to determine their morphology, particle size distribution and magnetic properties. The morphology of iron particles were observed using Field Emission Scanning Electron Microscope. The particle size distribution was measured using particle size analyzer. The magnetic properties of different iron particles were measured using vibrating sample magnetometer. In the first part of this study, optimal dimensions of MR damper and composition of MRF suitable for MR damper were determined. A shear mode monotube MR damper was designed by using optimization technique. A damper was manufactured in accordance with the optimized size and was filled with commercially available commercial MR fluid, MRF 132DG (Lord Corporation) to determine its damping characteristics using damper testing machine. Experimentally determined values were validated with computational ones. Further, six MR fluid samples (MRFs) were prepared composed of combination of three different particle mass fractions and two sizes of iron particles. Rheological tests were conducted on these samples to determine the flow curves at off-state and on-state magnetic field conditions and they were compared with those of commercial MR fluid, MRF 132DG (Lord Corporation). In addition, the sedimentation stability of prepared fluid were examined. These MRFs were filled in the MR damper and their damper characteristics were determined. The area bounded by the force-displacement graphs was used to calculate the energy dissipated which was then used to calculate equivalent damping coefficient. Finally, using multi-objective genetic algorithm (MOGA) optimization, based on maximization of on-state damping coefficient and minimization of off-state damping coefficient, the optimal mass fraction and particle size was determined. iv In the next part of the study, optimal dimensions of MR brake and composition of MRF suitable for MR brake were determined. At first, optimum dimensions of MR brake were computed considering the properties of commercially available MRF132DG fluid using MOGA optimization. Maximization of field induced braking torque and minimization of off-state torque were chosen as the objectives. This was performed in MATLAB software coupled with magnetostatic analyses in ANSYS APDL software. The braking torque of designed and fabricated MR brake utilizing commercial MR fluid, MRF 132DG (Lord Corporation) was experimentally determined and validated with computational ones. Selection of optimal composition of MRF was done considering In-house MR fluid samples composed of different combinations of particle mass fractions, mean particle diameters and base oil viscosities. A design of experiments technique was employed and braking torque corresponding to the synthesized MRFs at different speeds and current supplied along with the variation of shaft speed during braking process were measured. Based on the experimental results, MOGA optimization technique was used to determine optimal MR fluid composition with the objectives of maximizing field induced braking torque and minimizing off-state torque. Further, the effect of particle size and mass fraction of iron powder in the MRF on the vibration behaviour of MRF sandwich beams were studied. Six MRFs composed of combination of two particle sizes and three mass fractions of carbonyl iron powder were prepared and their viscoelastic properties were measured. The MRFs were used to fabricate different MRF core aluminium sandwich beams. Additionally, a sandwich beam with commercially available commercial MR fluid, MRF 132DG (Lord Corporation) as core was fabricated. The modal parameters of the cantilever MRF sandwich beams were determined at different magnetic fields. Further, sinusoidal sweep excitation tests were performed on these beams at different magnetic fields to investigate their vibration suppression behaviour. Finally, optimal particle size and mass fraction of iron powder suitable for sandwich beam were determined based on maximization of damping ratio and minimization of mass of MRF.