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Author: search.filters.author.Hegde, S.Subject: search.filters.subject.Plastics

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    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.
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    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.
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    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.
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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.