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Author: search.filters.author.Kumar, H.Subject: search.filters.subject.Design of experiments

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    Optimal Design of Rotary Magneto-Rheological Drum Brake for Transfemoral Prosthesis
    (Springer Science and Business Media Deutschland GmbH, 2021) Saini, R.S.T.; Kumar, H.; Chandramohan, S.; Sujatha, S.
    Semi-active technology offers good advantages in terms of controllability and adaptability. Magneto-rheological (MR) fluid is a class of smart fluids which display significant changes in its rheological properties under the influence of a magnetic field. Previous studies carried out using MR brake for the transfemoral prosthetic device were of multi-plate models which are complex in design and also to manufacture. Therefore, in the present study, a multi-coil rotary inverted drum brake is optimized with braking torque as the objective function. One of the advantages of the multi-coil design from multi-plate is that the former has fewer components and leads to a simpler design. The outermost geometric constraints are decided based on the knee cross-sections in anterior-posterior and mediolateral directions. Four design geometric variables are selected which are: coil depth, coil height, casing axial thickness, and casing radial thickness. A design of experiments technique is used to obtain 27 combinations of design variables. Magnetostatic analysis at each design point is performed and average flux densities in the annular and the radial gaps are determined. Regression analysis is conducted on the design data to obtain braking torque as a function of four design variables. Later, genetic algorithm is used to obtain the optimum geometric dimensions. A total maximum braking torque of 13.4 Nm is obtained using the optimum dimensions for a design current of 2 A. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Evaluation of optimal parameters of MR fluids for damper application using particle swarm and response surface optimisation
    (Springer Verlag service@springer.de, 2017) Gurubasavaraju, T.M.; Kumar, H.; Mahalingam, A.
    The controllable rheological properties of MR fluid exhibit viscoelastic properties within pre-yield, which are essential for the characterization of MR dampers for the isolation of vibration. In the present work, using particle swarm optimisation (PSO), it is identified that the proportion of MR fluid constituents, fluid gap and current are the parameters which influence majorly on the rheological properties and damping effect of MR damper. Initially, rheological properties of the prepared MR fluid samples are determined using rotational plate–plate type rheometer with the magnetorheological device cell attachment by keeping three levels of gap between the parallel plates. Three different proportions of MR fluid are prepared based on the volume fraction of carbonyl iron particle, i.e., 25, 30 and 35% in the silicone carrier fluid along with 1% of lithium-based grease as stabiliser. The objective function of this optimisation problem is to maximise the shear stress and damping force of the MR damper. The design of experiment (DOE) is employed to obtain the various combinations of parameters and their respective responses. The interaction of the regression model obtained from the DOE is used in PSO to evaluate the optimal parameters. The results indicated that the MR fluid with the particle concentration of 31% is the optimal proportion for MR damper application. © 2017, The Brazilian Society of Mechanical Sciences and Engineering.
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    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.
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    Determining the optimal composition of magnetorheological fluid for a short-stroke magnetorheological damper
    (Springer, 2023) Aralikatti, S.S.; Puneet, N.P.; Kumar, H.
    The current study investigates the effect of viscosity of base oil and weight fraction of carbonyl iron particles on maximum yield stress and effective damping range of a short-stroke magnetorheological damper (stroke length of 2 mm) designed for tool vibration mitigation. It is difficult to find the exact composition of magnetorheological fluid (MRF) based on the design equations, as unidentified practical parameters influence their behaviour hence, optimization by experimental techniques is necessary. Optimal composition of MRF are identified by genetic algorithm through central composite design of experiment. A validation study is conducted to cross verify the optimum values delivered by the algorithm. The damper is fitted onto lathe machine with the optimal fluid composition to evaluate its performance in controlling the tool vibration. The damper has been designed for the specific speed, feed and depth of cut however, the design procedure for developing a damper for higher/other cutting conditions can be achieved by the design scheme mentioned in this article. The vibration level of tool reduced by 28.66% and the amplitude of cutting force reduced by 68.18% indicating reduction of chatter vibration with the damper. An improved surface finish has been observed from 4.8 to 1.6 μm. © 2023, Indian Academy of Sciences.
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    Design and Development of Internal Wound Magnetorheological Elastomer Mount for Structural Vibration Isolation
    (Springer, 2025) Bhat, S.H.; Saroj, A.A.; Kumar, H.; Arun, M.; Vaidyanathan, R.V.
    Vibration isolation of structures is crucial for enhancing reliability when subjected to mechanical vibrations and shocks. This research investigates the application of Magneto-Rheological Elastomer (MRE) mounts to mitigate vibrations in a 15 kg structure. A unique MRE mount with internal windings was designed and developed using magneto-static analysis with maximizing magnetic flux density across MRE through the Design of Experiments (DoE). MRE samples were prepared considering 20, 40 and 60% (wt.) carbonyl iron particle (CIP) content within a silicon elastomer matrix and analyzed under a rheometer. Further, these MRE samples were considered for forced vibration studies with structures placed on MRE mounts across different frequencies. Repeated experiments with all in-house MRE samples demonstrated that the MRE mount significantly mitigated vibrations at different currents and compositions. The transmissibility plot revealed a maximum amplitude reduction of 3.73 times for the 60% MRE sample. These results underscore the importance of optimizing MRE mount and CIP content for effective vibration isolation, which is vital for prolonging the operational lifespan of critical structures. © The Institution of Engineers (India) 2025.