Faculty Publications
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Item Effect of shape and magnetocrystalline anisotropies in ordered Co nanorod arrays with smaller diameter(Elsevier, 2016) Boominathasellarajan, B.; Nagaraja, H.S.; Barshilia, H.C.; Chowdhury, P.Template assisted growth of Co nanorod arrays through electrochemical route was investigated. During this investigation, the template with nano-pore diameter was kept at a fixed value of 45 nm, whereas the length of the as grown nanorod array was varied from 25 to 400 nm keeping in mind that the aspect ratio (L/D) covers both below and above the unity. X-ray diffraction patterns indicate that the nanorod arrays initiate its textured growth with fcc (111) phase, however, the change in growth texture to hcp (100) was observed as it grows above 200 nm in length. The anisotropy fields extracted from the measured magnetization data reveal that a cross-over from in-plane to out-of-plane anisotropy takes place for L/D ?2.0. Based on the analytical approach, it seems that the shape anisotropy originated from the demagnetization factor with the change in geometry and magnetostatic interaction among the nanorods cause this crossover. However the micromagnetic simulation yields that both magnetocrystalline anisotropy and the magnetostatic interaction along with shape anisotropy are very much important to explain the experimental observations. © 2015 Elsevier B.V. All rights reserved.Item Optimisation of monotube magnetorheological damper under shear mode(Springer Verlag service@springer.de, 2017) Gurubasavaraju, T.M.; Kumar, H.; Mahalingam, M.Magnetorheological dampers (MR) are one of the semi active devices, which has the capability of providing variable damping force for the variable input current. Induced force is directly dependent on the amount of magnetic flux density developed in effective fluid flow gap of the MR damper. In the present work, influence of material properties on the magnetic flux is investigated by considering magnetic and nonmagnetic material for the outer cylinder of shear mode type MR damper. Magnetostatic analysis is carried out to obtain magnetic flux density for the initial configuration of the MR damper. From the analysis, it is found that usage of magnetic material cylinder which is insulated with nonmagnetic material provided higher value of magnetic flux and damping force. The geometric optimisation of MR damper is carried out to obtain the maximum flux density in the fluid flow gap. The objective function of the optimisation includes the maximum magnetic flux density and minimising fluid flow gap. Design variables considered are fluid flow gap, number of turns in the electromagnetic coil, length of the flange and DC current input. The optimisation is performed through response surface method using finite element analysis software (ANSYS). The best optimal design parameters are obtained by choosing the appropriate value of objective function. The best configuration of the design parameters, which induce the maximum magnetic flux density, is identified. The force induced in the MR damper is estimated analytically and a comparative study of the optimised and non-optimised results was carried out. © 2017, The Brazilian Society of Mechanical Sciences and Engineering.Item Static analysis of stepped functionally graded magneto-electro-elastic plates in thermal environment: A finite element study(Elsevier Ltd, 2017) Mahesh, M.; Kattimani, S.C.In this article, a finite element (FE) formulation accounting for multiphysics response of multilayered magneto-electro-elastic (MEE) plates in the thermal environment has been presented. The equilibrium equations of motion are attained using the principle of total potential energy and coupled constitutive relations of MEE material. Maxwell's equation of electrostatics and magnetostatics are used to model the electric and magnetic behavior. The influence of various through thickness temperature distributions on the static parameters of stepped functionally graded magneto-electro-elastic (SFG-MEE) plates is investigated. Further, an extra attention has been devoted to evaluate the effect of product properties (pyroelectric and pyromagnetic coupling), boundary conditions and aspect ratio on the direct (displacements, electric potential and magnetic potential) and derived quantities (stresses, electric displacement, and magnetic flux density) of the SFG-MEE plate. A comparative study is also carried out to analyse the effect of stacking sequence, boundary conditions, pyroeffects, length-to-width ratio and aspect ratios of the SFG-MEE plate. The credibility of the proposed FE model is verified with the results available in the literature. It is expected that the findings in this article may be useful for accurate design and analysis of MEE structures under the thermal environment. © 2017 Elsevier LtdItem An approach for characterizing twin-tube shear-mode magnetorheological damper through coupled FE and CFD analysis(Springer Verlag service@springer.de, 2018) Gurubasavaraju, T.M.; Kumar, H.; Mahalingam, A.The most promising technology in the field of semi-active suspension systems is the use of magnetorheological property of MR fluid, whose material behavior can be controlled through external magnetic field. Devices developed based on this principle are adaptive and controllable as desired for a specific application. It is important to understand the damping characteristics of these devices before employing them, using experimental or computational approaches. In the present work, both experimental and computational methods have been adopted for characterizing a twin-tube MR damper with an intention to develop a computational approach as an alternative to experimental test in the preliminary design stage. Initially, experimental characterization of MR damper was carried out at 1.5 and 2 Hz frequencies for damper stroke length of ± 5 mm under different DC currents ranging from 0.1 to 0.4 A. Later, coupled finite-element and computational fluid dynamic analysis has been carried out to estimate the damping force under same conditions as used in the experiment. The results of computation are in good agreement with experimental ones. Furthermore, using this computational approach, the damping force at different frequencies of 1.5, 2, 3, and 4 Hz has been estimated and its time histories are also plotted. The influence of fluid flow gap on the damping force has been determined and results revealed that damping force behaves inversely with fluid flow gap. © 2018, The Brazilian Society of Mechanical Sciences and Engineering.Item Performance analysis of a semi-active suspension system using coupled CFD-FEA based non-parametric modeling of low capacity shear mode monotube MR damper(SAGE Publications Ltd, 2019) Gurubasavaraju, G.; Kumar, H.; Mahalingam, A.In this work, an approach for formulation of a non-parametric-based polynomial representative model of magnetorheological damper through coupled computational fluid dynamics and finite element analysis is presented. Using this, the performance of a quarter car suspension subjected to random road excitation is estimated. Initially, prepared MR fluid is characterized to obtain a relationship between the field-dependent shear stress and magnetic flux density. The amount of magnetic flux induced in the shear gap of magnetorheological damper is computed using finite element analysis. The computed magnetic field is used in the computational fluid dynamic analysis to calculate the maximum force induced under specified frequency, displacement and applied current using ANSYS CFX software. Experiments have been conducted to verify the credibility of the results obtained from computational analysis, and a comparative study has been made. From the comparison, it was found that a good agreement exists between experimental and computed results. Furthermore, the influence of fluid flow gap length and frequency on the induced force of the damper is investigated using the computational methods (finite element analysis and computational fluid dynamic) for various values. This proposed approach would serve in the preliminary design for estimation of magnetorheological damper dynamic performance in semi-active suspensions computationally prior to experimental analysis. © IMechE 2018.Item Investigation of magnetorheological brake with rotor of combined magnetic and non-magnetic materials(Springer Nature, 2019) Acharya, S.; Kumar, H.Magnetorheological (MR) brakes are a type of electromagnetic brakes that make use of controllable viscoelastic properties of magnetorheological fluid for braking. The torque capacity of the MR brake depends on the magnitude of magnetic flux density generated in the MR fluid. In this study, the effect of combination of magnetic and non-magnetic materials for rotor disk of MR brake with the objective to maximizing the flux density in the MR fluid gap at the rotor periphery was investigated. Initially, the MR brake rotor disk radius and MR fluid gap thickness were determined by using Genetic Algorithm optimization technique for desired torque ratio and torque capacity. Magnetostatic analyses were performed at different current magnitudes to determine the magnetic field and flux density in the MR brake. Further, to enhance the magnetic field intensity in the MR fluid at the rotor periphery, the rotor was modeled with three different configurations of MR brake with combinations of magnetic and non-magnetic steel and magnetostatic analyses of the MR brake were performed. It was found that the leakage of flux away from rotor periphery was reduced and there is significant increase and concentration of the magnetic field and flux density in the MR fluid gap through the use of rotor disk with combined magnetic and non-magnetic materials which would subsequently increase the torque capacity of the MR brake. © 2019, Springer Nature Switzerland AG.Item Determination of optimal magnetorheological fluid particle loading and size for shear mode monotube damper(Springer Verlag service@springer.de, 2019) Acharya, S.; Saini, R.S.S.; Kumar, H.Magnetorheological (MR) fluids belong to a class of controllable fluids, and the composition and concentration of its components govern its magnetorheological properties. In this study, an optimum particle loading (or mass fraction) and size of iron particles in MR fluid for use in a shear mode monotube MR damper were determined based on the damping force and off-state viscosity of synthesized MR fluid samples. Initially, the morphological and magnetic properties of carbonyl iron particles were characterized. Six MR fluid samples were prepared composed of combination of three different particle loadings and two sizes of iron particles. Magnetorheological tests were conducted on these samples to determine the flow curves at off-state and on-state magnetic field conditions. Herschel–Bulkley model was used for mathematical representation of flow curves at different magnetic fields and to determine their dynamic yield stress. Further, a shear mode monotube MR damper with accumulator was designed by using optimization technique for desired dynamic range and damping force. Magnetostatic analysis was performed to determine the magnetic field strength generated in the shear gap at different currents. The damping force was calculated for synthesized MR fluids based on their dynamic yield stress corresponding to the magnetic field strength in the shear gap. Analysis of variance was performed to analyse the significance of independent factors on the damping force and off-state viscosity of MRF. The optimal particle loading and size which yielded maximum damping force with minimum off-state viscosity were determined using a multi-objective genetic algorithm. © 2019, The Brazilian Society of Mechanical Sciences and Engineering.Item Optimal design of inverted rotary MR brake with waveform boundary using a novel combined magnetostatic approach(IOP Publishing Ltd, 2020) Saini, R.S.T.; Kumar, H.; Chandramohan, S.In the present work, an inverted rotary drum magneto rheological (MR) brake with waveform arc boundary suitable for prosthetic knee application is optimally designed. Often, the magnetostatic analysis is performed assuming linear magnetic systems and solving a lumped parametric equivalent magnetic model (EMM). Although, this reduces the computational time but compromises the accuracy of the solution. On the other hand, finite element magnetostatic (FEMS) analysis combined with a search-based optimization technique requires more time and effort. In this work, an approach combining the EMM and FEMS methods is proposed to optimally design the MR brake. This method requires the optimization algorithm to maintain an external repository so that individuals which are non-dominated at each generation get stored in the repository and only those individuals are allowed to use FEMS method. This approach reduces the number of function calls made to FEMS method and thus reduces the computational time substantially. A recently proposed multi-objective particle swarm optimization (MOPSO) which evaluates the global best using minimum distance of point of line (MDPL) method is implemented with the proposed combined magnetostatic method. While FEMS method alone resulted in an average computational time of 7.25 h, the proposed method evaluated a similar Pareto front solution in 38 min. Finally, the optimal design is compared to other prosthetic knee MR brakes from the literature. © 2020 IOP Publishing Ltd.Item Selection of optimal composition of MR fluid for a brake designed using MOGA optimization coupled with magnetic FEA analysis(SAGE Publications Ltd, 2021) Acharya, S.; Saini, T.R.S.; Sundaram, V.; Kumar, H.The design of Magnetorheological (MR) brake and the composition of MR fluid (MRF) used in it have a significant effect on its performance and hence an effort has been made in this study to determine the optimal dimensions of MR brake and composition of MRF suitable for the brake application. Initially, optimum parameters of MR brake were computed considering the properties of commercially available MRF 132DG fluid using multi-objective genetic algorithm (MOGA) optimization. This was performed in MATLAB software coupled with magnetostatic analyses in ANSYS APDL software. The braking torque of designed MR brake utilizing MRF 132DG fluid was experimentally determined and validated with analytical ones. Further, selection of optimal composition of MRF was done considering In-house MRF samples composed of different combinations of particle mass fractions, mean particle diameters and base oil viscosities. A design of experiments (DOE) technique was employed and braking torque corresponding to the synthesized MRF samples at different speeds and current supplied were measured along with the variation of shaft speed during braking process. Grounded on the experimental results, using MOGA optimization technique, MRF composed of smaller sized iron particles (2.91 microns) with mass fraction of 80.95% and lower viscosity base oil (50 cSt) was selected as optimal composition of MRF for use in MR brake. Maximization of field induced braking torque and minimization of off-state torque were chosen as the objective functions for both the optimal design of MR brake and selection of optimal composition of MRF. Finally, the sedimentation stability of MRFs were investigated. © The Author(s) 2020.Item Study on operational temperature of magneto-rheological fluid and design dimensions of magneto-rheological damper for optimization(Institute of Physics, 2024) Kumar Kariganaur, A.; Kumar, H.; Arun, M.This study aims to restrict the upper limit for flow gap and effective length in magnetorheological (MR) damper for optimal performance. Initially, the sedimentation study of in-house MR fluid (25%) shows that an 8% reduction in the sedimentation ratio with the addition of additive and nonlinear Herschel-Bulkley (HB) model fit reflects a 32.5% decrease in average yield stress with increasing currents when the parallel plate gap is increased from 1 mm to 2 mm. Owing to this decrease in yield stress, further study is extended to fabricate two MR dampers with limit values (LV) of flow gap and effective length with a common magnetic outer cylinder. Testing results of MR dampers revealed a 72% reduction in damping force at 0.8 A current when the LV’s is increased from LV-1 to LV-2. Selecting LV-1 over LV-2 as the upper limit for any design optimization will give the MR damper optimal performance. At higher input parameters, amplitude has a 135% greater impact on damping force than frequency and current. It is also demonstrated that saturation magnetization depends on the applied magnetic field and input loading parameters. Finally, gravimetric analysis shows that the effectiveness of the MR fluid and magnetic particle starts to decline after 322 °C and 400 °C. © 2024 IOP Publishing Ltd.