Browsing by Author "Poojary, U.R."

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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.
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).
Dynamic blocked transfer stiffness method of characterizing the magnetic field and frequency dependent dynamic viscoelastic properties of MRE
(2016) Poojary, U.R.; Hegde, S.; Gangadharan, K.V.
Magneto rheological elastomer (MRE) is a potential resilient element for the semi active vibration isolator. MRE based isolators adapt to different frequency of vibrations arising from the source to isolate the structure over wider frequency range. The performance of MRE isolator depends on the magnetic field and frequency dependent characteristics of MRE. Present study is focused on experimentally evaluating the dynamic stiffness and loss factor of MRE through dynamic blocked transfer stiffness method. The dynamic stiffness variations of MRE exhibit strong magnetic field and mild frequency dependency. Enhancements in dynamic stiffness saturate with the increase in magnetic field and the frequency. The inconsistent variations of loss factor with the magnetic field substantiate the inability of MRE to have independent control over its damping characteristics. 2016 The Korean Society of Rheology and Springer.
Dynamic blocked transfer stiffness method of characterizing the magnetic field and frequency dependent dynamic viscoelastic properties of MRE
(Korean Society of Rheology, 2016) Poojary, U.R.; Hegde, S.; Gangadharan, K.V.
Magneto rheological elastomer (MRE) is a potential resilient element for the semi active vibration isolator. MRE based isolators adapt to different frequency of vibrations arising from the source to isolate the structure over wider frequency range. The performance of MRE isolator depends on the magnetic field and frequency dependent characteristics of MRE. Present study is focused on experimentally evaluating the dynamic stiffness and loss factor of MRE through dynamic blocked transfer stiffness method. The dynamic stiffness variations of MRE exhibit strong magnetic field and mild frequency dependency. Enhancements in dynamic stiffness saturate with the increase in magnetic field and the frequency. The inconsistent variations of loss factor with the magnetic field substantiate the inability of MRE to have independent control over its damping characteristics. © 2016 The Korean Society of Rheology and Springer.
Dynamic deformation dependent magnetic field induced force transmissibility characteristics of magnetorheological elastomer
(2017) Poojary, U.R.; Hegde, S.; Gangadharan, K.V.
The need for broad-band vibration isolation performance of the structures is fulfilled by magnetorheological elastomer based smart vibration isolation system. The smart isolation capabilities of magnetorheological elastomer isolator vary with the input dynamic deformation levels. In this study, force transmissibility measurement approach is adapted to evaluate the influence of dynamic deformation on the field-induced isolation capabilities of magnetorheological elastomer. The variation in isolation capabilities of magnetorheological elastomer is assessed in terms of isolation effect. Isolation performance of magnetorheological elastomer is enhanced with the increase in the magnetic field. Under increased dynamic deformation levels, the isolation characteristics of magnetorheological elastomer are influenced by the Payne effect. Dominance of the Payne effect under non-magnetized state of magnetorheological elastomer has enhanced the isolation effect at larger strain levels. The influence of strain on isolation characteristics of magnetorheological elastomer is verified from the magnetic force simulation between a pair of dipoles performed in ANSYS (version 14). 2016, The Author(s) 2016.
Dynamic deformation–dependent magnetic field–induced force transmissibility characteristics of magnetorheological elastomer
(SAGE Publications Ltd info@sagepub.co.uk, 2017) Poojary, U.R.; Hegde, S.; Gangadharan, K.V.
The need for broad-band vibration isolation performance of the structures is fulfilled by magnetorheological elastomer–based smart vibration isolation system. The smart isolation capabilities of magnetorheological elastomer isolator vary with the input dynamic deformation levels. In this study, force transmissibility measurement approach is adapted to evaluate the influence of dynamic deformation on the field-induced isolation capabilities of magnetorheological elastomer. The variation in isolation capabilities of magnetorheological elastomer is assessed in terms of isolation effect. Isolation performance of magnetorheological elastomer is enhanced with the increase in the magnetic field. Under increased dynamic deformation levels, the isolation characteristics of magnetorheological elastomer are influenced by the Payne effect. Dominance of the Payne effect under non-magnetized state of magnetorheological elastomer has enhanced the isolation effect at larger strain levels. The influence of strain on isolation characteristics of magnetorheological elastomer is verified from the magnetic force simulation between a pair of dipoles performed in ANSYS (version 14). © 2016, © The Author(s) 2016.
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.
Experimental investigation on the effect of carbon nanotube additive on the field-induced viscoelastic properties of magnetorheological elastomer
(2018) Poojary, U.R.; Hegde, S.; Gangadharan, K.V.
The additives improve the properties of magnetorheological elastomer by modifying the surface of ferromagnetic filler particles or by varying the properties of a host polymer matrix. In this study, effect of carbon nanotube additive on the viscoelastic properties of magnetorheological elastomer reinforced with optimum quantity of ferromagnetic filler is studied. Room temperature vulcanizing silicone elastomer-based test samples are prepared by mixing the elastomer with the carbon nanotube and carbonyl iron powder blend obtained from ultrasonication. Viscoelastic properties are measured by adopting the dynamic blocked transfer stiffness method. The results revealed that the properties of magnetorheological elastomer vary significantly with the inclusion of carbon nanotube. With the addition of 0.5 wt% carbon nanotube, the zero field dynamic stiffness of magnetorheological elastomer is enhanced by 36.7% and the loss factor is increased by 17.2%. The enhancement in zero field properties led to the least field-induced enhancement for magnetorheological elastomer doped with 0.5 wt% carbon nanotube. A relatively larger flexibility of pure magnetorheological elastomer samples had resulted in the maximum field-induced enhancement of 48.04%. Among the prepared test samples with carbon nanotube addition, the sample loaded with 0.25 wt% carbon nanotube exhibited a pronounced stiffness enhancement and lower loss factor. This substantiated the existence of an optimum limit for carbon nanotube additive. The present study also confirmed the feasibility of developing MRE tailor-made to suit the particular application by selecting a proper composition of matrix, filler and the additives. 2017, Springer Science+Business Media, LLC, part of Springer Nature.
Experimental investigation on the effect of carbon nanotube additive on the field-induced viscoelastic properties of magnetorheological elastomer
(Springer New York LLC barbara.b.bertram@gsk.com, 2018) Poojary, U.R.; Hegde, S.; Gangadharan, K.V.
The additives improve the properties of magnetorheological elastomer by modifying the surface of ferromagnetic filler particles or by varying the properties of a host polymer matrix. In this study, effect of carbon nanotube additive on the viscoelastic properties of magnetorheological elastomer reinforced with optimum quantity of ferromagnetic filler is studied. Room temperature vulcanizing silicone elastomer-based test samples are prepared by mixing the elastomer with the carbon nanotube and carbonyl iron powder blend obtained from ultrasonication. Viscoelastic properties are measured by adopting the dynamic blocked transfer stiffness method. The results revealed that the properties of magnetorheological elastomer vary significantly with the inclusion of carbon nanotube. With the addition of 0.5 wt% carbon nanotube, the zero field dynamic stiffness of magnetorheological elastomer is enhanced by 36.7% and the loss factor is increased by 17.2%. The enhancement in zero field properties led to the least field-induced enhancement for magnetorheological elastomer doped with 0.5 wt% carbon nanotube. A relatively larger flexibility of pure magnetorheological elastomer samples had resulted in the maximum field-induced enhancement of 48.04%. Among the prepared test samples with carbon nanotube addition, the sample loaded with 0.25 wt% carbon nanotube exhibited a pronounced stiffness enhancement and lower loss factor. This substantiated the existence of an optimum limit for carbon nanotube additive. The present study also confirmed the feasibility of developing MRE tailor-made to suit the particular application by selecting a proper composition of matrix, filler and the additives. © 2017, Springer Science+Business Media, LLC, part of Springer Nature.
Experimental investigation on the effect of magnetic field on strain dependent dynamic stiffness of magnetorheological elastomer
(2016) Poojary, U.R.; Gangadharan, K.V.
Magnetorheological elastomer (MRE), which belongs to the family of filled elastomer, tends to exhibit strain dependent characteristics under dynamic loading. The strain dependency in MRE is different compared to the conventional filled elastomers, as the magnetic field induced interactions between the fillers impart additional complexities. In the present study, the strain dependent characteristic of isotropic MRE is evaluated from the variation in the dynamic blocked transfer stiffness measured from the force displacement system Lissajous plots. Experiments are performed at different strain levels by varying the magnetic field and the excitation frequency. Results of experiments revealed the disparity in strain dependent characteristics of MRE under magnetized and non-magnetized state. The strain dependency is more pronounced under non-magnetized state of MRE. Within the tested strain level, the field induced property enhancement in MRE is increased with an increase in strain. This difference in strain dependent characteristic of MRE is interpreted by adapting bound rubber model. 2016, Springer-Verlag Berlin Heidelberg.
Experimental investigation on the effect of magnetic field on strain dependent dynamic stiffness of magnetorheological elastomer
(Springer Verlag service@springer.de, 2016) Poojary, U.R.; Gangadharan, K.V.
Magnetorheological elastomer (MRE), which belongs to the family of filled elastomer, tends to exhibit strain dependent characteristics under dynamic loading. The strain dependency in MRE is different compared to the conventional filled elastomers, as the magnetic field induced interactions between the fillers impart additional complexities. In the present study, the strain dependent characteristic of isotropic MRE is evaluated from the variation in the dynamic blocked transfer stiffness measured from the force displacement system Lissajous plots. Experiments are performed at different strain levels by varying the magnetic field and the excitation frequency. Results of experiments revealed the disparity in strain dependent characteristics of MRE under magnetized and non-magnetized state. The strain dependency is more pronounced under non-magnetized state of MRE. Within the tested strain level, the field induced property enhancement in MRE is increased with an increase in strain. This difference in strain dependent characteristic of MRE is interpreted by adapting bound rubber model. © 2016, Springer-Verlag Berlin Heidelberg.
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.
Integer and fractional order-based viscoelastic constitutive modeling to predict the frequency and magnetic field-induced properties of magnetorheological elastomer
(2018) Poojary, U.R.; Gangadharan, K.V.
Magnetorheological elastomer (MRE)-based semi-active vibration mitigation device demands a mathematical representation of its smart characteristics. To model the material behavior over broadband frequency, the simplicity of the mathematical formulation is very important. Material modeling of MRE involves the theory of viscoelasticity, which describes the properties intermediate between the solid and the liquid. In the present study, viscoelastic property of MRE is modeled by an integer and fractional order derivative approaches. Integer order-based model comprises of six parameters, and the fraction order model is represented by five parameters. The parameters of the model are identified by minimizing the error between the response from the model and the dynamic compression test data. Performance of the model is evaluated with respect to the optimized parameters estimated at different sets of regularly spaced arbitrary input frequencies. A linear and quadratic interpolation function is chosen to generalize the variation of parameters with respect to the magnetic field and frequency. The predicted response from the model revealed that the fractional order model describes the properties of MRE in a simplest form with reduced number of parameters. This model has a greater control over the real and imaginary part of the complex stiffness, which facilitates in choosing a better interpolating function to improve the accuracy. Furthermore, it is confirmed that the realistic assessment on the performance of a model is based on its ability to reproduce the results obtained from optimized parameters. Copyright 2018 by ASME.
Integer and fractional order-based viscoelastic constitutive modeling to predict the frequency and magnetic field-induced properties of magnetorheological elastomer
(American Society of Mechanical Engineers (ASME), 2018) Poojary, U.R.; Gangadharan, K.V.
Magnetorheological elastomer (MRE)-based semi-active vibration mitigation device demands a mathematical representation of its smart characteristics. To model the material behavior over broadband frequency, the simplicity of the mathematical formulation is very important. Material modeling of MRE involves the theory of viscoelasticity, which describes the properties intermediate between the solid and the liquid. In the present study, viscoelastic property of MRE is modeled by an integer and fractional order derivative approaches. Integer order-based model comprises of six parameters, and the fraction order model is represented by five parameters. The parameters of the model are identified by minimizing the error between the response from the model and the dynamic compression test data. Performance of the model is evaluated with respect to the optimized parameters estimated at different sets of regularly spaced arbitrary input frequencies. A linear and quadratic interpolation function is chosen to generalize the variation of parameters with respect to the magnetic field and frequency. The predicted response from the model revealed that the fractional order model describes the properties of MRE in a simplest form with reduced number of parameters. This model has a greater control over the real and imaginary part of the complex stiffness, which facilitates in choosing a better interpolating function to improve the accuracy. Furthermore, it is confirmed that the realistic assessment on the performance of a model is based on its ability to reproduce the results obtained from optimized parameters. © © 2018 by ASME.
Magnetic field and frequency dependent LVE limit characterization of magnetorheological elastomer
(2017) Poojary, U.R.; Gangadharan, K.V.
Magnetorheological elastomer (MRE) based semi-active isolators have the potential to replace conventional passive isolators to achieve wide frequency range isolation. The effectiveness of MRE isolator depends on the control strategies developed based on viscoelastic constitutive relations. The theory of linear viscoelasticity is the basis for viscoelastic constitutive relations which can predict the material behavior within a certain strain limit referred as linear viscoelastic (LVE) limit. Beyond the LVE limit, the performance of MRE semi-active isolator exacerbates as the control strategies turns out to be ineffective. In the present study, variation in LVE limit of MRE with the magnetic field and frequency is investigated through forced vibration tests. To exclude the effect of terminal non-linearity on the measurement, the blocked transfer stiffness method described in the ISO 10846-2 is adopted. The results revealed that the LVE limit of MRE is strongly dependant on the magnetic field and exhibited a weak dependency on the operating frequency. Under magnetized state, the transition from linear to non-linear behavior of MRE is at lower strain levels indicating the increased friction energy dissipation at particle matrix interface. 2016, The Brazilian Society of Mechanical Sciences and Engineering.
Magnetic field and frequency dependent LVE limit characterization of magnetorheological elastomer
(Springer Verlag service@springer.de, 2017) Poojary, U.R.; Gangadharan, K.V.
Magnetorheological elastomer (MRE) based semi-active isolators have the potential to replace conventional passive isolators to achieve wide frequency range isolation. The effectiveness of MRE isolator depends on the control strategies developed based on viscoelastic constitutive relations. The theory of linear viscoelasticity is the basis for viscoelastic constitutive relations which can predict the material behavior within a certain strain limit referred as linear viscoelastic (LVE) limit. Beyond the LVE limit, the performance of MRE semi-active isolator exacerbates as the control strategies turns out to be ineffective. In the present study, variation in LVE limit of MRE with the magnetic field and frequency is investigated through forced vibration tests. To exclude the effect of terminal non-linearity on the measurement, the blocked transfer stiffness method described in the ISO 10846-2 is adopted. The results revealed that the LVE limit of MRE is strongly dependant on the magnetic field and exhibited a weak dependency on the operating frequency. Under magnetized state, the transition from linear to non-linear behavior of MRE is at lower strain levels indicating the increased friction energy dissipation at particle–matrix interface. © 2016, The Brazilian Society of Mechanical Sciences and Engineering.
Material modeling of frequency, magnetic field and strain dependent response of magnetorheological elastomer
(Springer, 2021) Poojary, U.R.; Gangadharan, K.V.
Accurate modeling of material behavior is very critical for the success of magnetorheological elastomer-based semi-active control device. The material property of magnetorheological elastomer is sensitive to the frequency, magnetic field and the input strain. Additionally, these properties are unique for a particular combination of matrix and the filler loading. An experimental-based characterization approach is costly and time consuming as it demands a large amount of experimental data. This process can be simplified by adopting material modeling approach. The material modeling of magnetorheological elastomer is an extension of conventional viscoelastic constitutive relations coupled with hysteresis and magnetic field sensitive attributes. In the present study, a mathematical relation to represent the frequency, magnetic field and strain dependent behavior of magnetorheological elastomer is presented. The viscoelastic behavior is represented by a fractional zener element and the magnetic field and strain dependent attributes incorporated in the model by a magnetic spring and linearized Bouc-–Wen element, respectively. The proposed model comprised of a total of eight parameters, which are identified by minimizing the least square error between the model predicted and the experimental response. The variations of each parameter with respect to the operating conditions are represented by a generalized expression. The parameters estimated from the generalized expression are used to assess the ability of the model in describing the dynamic response of magnetorheological elastomer. The proposed model effectively predicted the stiffness characteristics with an accuracy, more than 94.3% and the corresponding accuracy in predicting the damping properties is above 90.1%. This model is capable of fitting the experimental value with a fitness value of more than 93.22%. © 2021, The Author(s).