Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
8 results
Search Results
Item Modelling of frictional damper with equivalent viscous damper(American Institute of Physics Inc. subs@aip.org, 2020) Kiran, K.; Gangadharan, K.V.Damping is always an important factor for any vibrating system. It is required to add this element, since it reduces the amplitude of vibrations at natural frequency and improves the amount energy dissipation with initial disturbances. Developing a mathematical model for the frictional damper is complex because of the combination of the damping present in the system. Currently, many models such as Bingham's model, Lu-Gre Model and Bouc-Wen are developed for mathematical representation of friction damper. However, finding the parameters of these models is a cumbersome process. The simplest method is to represent it as an equivalent viscous damper. Presently, in this work, using parametric modeling, combined damping behavior of the frictional damper was identified using MATLAB SIMULINK parametric estimation toolkit. Then after, combined behavior of the friction damper was modelled into an equivalent viscous damping. Finally, this equivalent viscous damping was represented as other equivalent damping types. © 2020 Author(s).Item Health seeking behavior in Karnataka: Does micro-health insurance matter?(2013) Basri, S.; Kiran, K.Background: Health seeking behaviour in the event of illness is influenced by the availability of good health care facilities and health care financing mechanisms. Micro health insurance not only promotes formal health care utilization at private providers but also reduces the cost of care by providing the insurance coverage. Objectives: This paper explores the impact of Sampoorna Suraksha Programme, a micro health insurance scheme on the health seeking behaviour of households during illness in Karnataka, India. Materials and Methods: The study was conducted in three randomly selected districts in Karnataka, India in the first half of the year 2011. The hypothesis was tested using binary logistic regression analysis on the data collected from randomly selected 1146 households consisting of 4961 individuals. Results: Insured individuals were seeking care at private hospitals than public hospitals due to the reduction in financial barrier. Moreover, equity in health seeking behaviour among insured individuals was observed. Conclusion : Our finding does represent a desirable result for health policy makers and micro finance institutions to advocate for the inclusion of health insurance in their portfolio, at least from the HSB perspective.Item A novel approach to investigate effect of magnetic field on dynamic properties of natural rubber based isotropic thick magnetorheological elastomers in shear mode(Central South University of Technology f-ysxb@mail.csut.edu.cn, 2015) Hegde, S.; Kiran, K.; Gangadharan, K.V.The preparation of natural rubber based isotropic thick magnetorheological elastomers (MRE) was focused on by varying the percentage volume concentration of carbonyl iron powder and developing a test set up to test the dynamic properties. Effect of magnetic field on the damping ratio was studied on the amplification region of the transmissibility curve. The viscoelastic dynamic damping nature of the elastomer was also studied by analyzing the force-displacement hysteresis graphs. The results show that MR effect increases with the increase in magnetic field as well as carbonyl iron powder particle concentration. It is observed that softer matrix material produces more MR effect. A maximum of 125% improvement in the loss factor is observed for the MRE with 25% carbonyl iron volume concentration. FEMM simulation shows that as carbonyl iron particle distribution becomes denser, MR effect is improved. FEMM analysis also reveals that if the distance between the adjacent iron particles are reduced from 20 ?m to 10 ?m, a 40% increase in stored energy is observed. © 2014, Central South University Press and Springer-Verlag Berlin Heidelberg.Item Dynamic response of a MRE sandwich structure under a non-homogenous magnetic field(Korean Physical Society, 2021) Poojary, U.R.; Hegde, S.; Kiran, K.; Gangadharan, K.V.A viscoelastic layer improves the response of a sandwich structure under dynamic loading. Through integration of a magneto-sensitive elastomer core, the adaptability of the structure over a wider frequency can be achieved. The current work focuses on the influence of a non-homogeneous magnetic field on a magnetorheological elastomer (MRE)-based sandwich cantilever beam. The dynamic response of the structure is measured using the impact hammer test as per the ASTM E-756-05 standard. Results revealed that the fundamental natural frequency of the MRE sandwich beam is a function of the intensity and the location of the non-homogenous magnetic field. The fundamental natural frequency is reduced as the magnitude of the magnetic flux density is increased or the magnetized region is shifted towards the fixed end. This unique response of the MRE sandwich beam under a non-homogenous magnetic field is an exception to the usual stiffness-enhancing behavior of a MRE. To study this disparity, we independently investigated the contributions by the localized stiffness enhancement and the deflection due to magnetic pull. The effect of the localized overall stiffness enhancement on the overall stiffness of the sandwich beam is investigated using modal analysis in ANSYS to analyze the variation in the fundamental frequency. The contribution due to magnetic pull is studied by performing an experimental modal analysis on an equivalent ferromagnetic cantilever beam deflected under the influence of a magnetic field. By comparing the experimental results and the corresponding investigation on the influencing factors, we confirmed that magnetic pull induced under non-homogenous magnetic field is an important parameter that significantly contributes to the dynamic response of a MRE sandwich beam. © 2021, The Korean Physical Society.Item Developing the viscoelastic model and model-based fuzzy controller for the MRE isolator for the wide frequency range vibration isolation(Springer Science and Business Media Deutschland GmbH, 2022) Kiran, K.; Poojary, U.R.; Gangadharan, K.V.The ability to mitigate the vibrations by a magnetorheological elastomer (MRE) isolator varies with the amplitude of the excitation and the magnetic field. To implement semi-active vibration control, a mathematical model representing the dynamic response over a wide frequency range is crucial. In the present study, an attempt was made to develop a mathematical model for the designed MRE isolator over a wide frequency range under different operating conditions. A model-based fuzzy controller was developed to implement semi-active control attributes over a broadband frequency. The methodology entails that the MRE isolator operating in shear mode was designed. The performance of the isolator was evaluated over a frequency range of 15–80 Hz with varying input currents and excitation amplitudes. The transmissibility response of MRE isolator was mathematically represented using viscoelastic constitutive relations. The isolator system was represented in state-space form, and its parameters were determined by minimizing the mean square error between experimental and model responses. A polynomial function was used to generalize variations in viscoelastic model parameters with respect to the input current. Based on the controller stopping frequency, a relationship was established between the current input to the MRE isolator and the excitation amplitude. Using the mathematical equations, a model-based fuzzy controller was developed and tested in simulation and real-time conditions. The results show that the controller effectively isolates the vibration amplitude at various excitation amplitudes and frequencies. © 2022, The Author(s).Item Fractional-order viscoelastic modeling of the magnetic field dependent transmissibility response of MRE isolator(SAGE Publications Ltd, 2022) Kiran, K.; Poojary, U.R.; Gangadharan, K.V.In the present study, a modeling approach to estimate the parameters of the MRE isolator model with respect to the frequency-response curve is presented. To concur the response of the isolator over wide frequency range, fractional order based Kelvin Voigt model comprised of three parameters and the fractional Zener model having four parameters are proposed. An isolator operating in shear-mode is developed, and its performance is evaluated through the transmissibility tests. The parameters of the model are identified by minimizing the error between the transmissibility response from the MRE isolator model and the experimental results. A polynomial function is used to generalize the variation of these parameters with respect to the input current. The response predicted by the MRE isolator models confirms that both fractional Kelvin Voigt and fractional Zener modeling approaches are effective in portraying the transmissibility response. The fractional Zener MRE isolator model is more accurate and can reproduce the experimentally determined magnitude and phase response of the transmissibility with an accuracy greater than 91.5% and 84.87% respectively. On the contrary, the fractional Kelvin Voigt model is simpler in form, and it effectively reproduced the magnitude of the transmissibility response with an accuracy higher than 86.35% and the phase response greater than 83.77%. © The Author(s) 2022.Item Static, buckling, and free vibration characteristics of porous skew partially functionally graded magneto-electro-elastic plate(Taylor and Francis Ltd., 2023) Kiran, K.; Wang, W.; Fang, C.; Kattimani, S.In this article, a new mathematical model to develop porous skew partially functionally graded (SPFG) magneto-electro-elastic (MEE) plate from a stepped functionally grade (SFG) plate is proposed. The combination of Barium Titanate (BaTiO3) and Cobalt Ferrite (CoFe2O4) is graded stepwise to achieve SFG plates. Such, SFG plate is approximated using modified power law for functional variation through its thickness. Modified first-order shear deformation theory (FSDT) is deployed in the current study to develop mathematical models. The geometrical modification from rectangular to skew plate is achieved using transformation matrix. Porosity in the partial functionally graded MEE plate is taken as local density. Free vibration study is carried out to reflect the influence of partial gradation, porosity distribution, porosity volume, and skew angle on the natural frequency of porous SPFG MEE plate. The influence of various types of porosity distribution, partial gradation, and skew angle on the primary quantities such as displacements, potentials, and secondary quantities such as stresses, electric displacement, and magnetic induction on SPFG MEE plate is studied. The stability characteristics of the SPFG MEE plate are also investigated to study the buckling behavior under various porosity distributions, partial gradation, and skew angles. The effect of change in aspect ratio, and thickness ratio on the free vibration and static behavior is also investigated. © 2021 Taylor & Francis Group, LLC.Item An experimental investigation on the matrix dependent rheological properties of MRE(SAGE Publications Ltd, 2024) Poojary, U.R.; Kiran, K.; Hegde, S.; Gangadharan, K.V.The rheological properties of magnetorheological elastomers are influenced by magnetically sensitive fillers and the elastomer matrix. The ability to respond to an external magnetic field is imparted by the fillers, while the load-bearing capability is determined by the matrix type. In this paper, the effect of matrix material on the properties of magnetorhological elastomer is explored experimentally. Carbonyl iron particle content is varied by 0%, 15% and 25% by volume to produce magnetorheological elastomer samples using natural rubber, silicone rubber and nitrile butadiene rubber matrices. Forced transmissibility test approach was employed to evaluate the field induced variations in the dynamic stiffness and loss factor of magnetorheological elastomers. The dynamic stiffness of nitrile butadiene rubber is the highest, while that of silicone rubber is the lowest. Addition of carbonyl iron particles significantly improves stiffness, although these gains depend on the properties of unfilled matrix. The addition of 25% by volume of carbonyl iron particle increased the dynamic stiffness of a silicone rubber matrix based magnetorheological elastomer by 67.78%, while the similar change in magnetorheological elastomer with nitrile butadiene rubber matrix was 38.58%. The field dependent response of magnetorheological elastomers is governed by the matrix and ferromagnetic filler concentration. These qualities are higher in magnetorheological elastomer with a low initial dynamic stiffness matrix and lower in magnetorheological elastomers with a stiffer matrix. © The Author(s) 2023.