On Love-type waves in a finitely deformed magnetoelastic layered half-space

In this paper, the propagation of Love-type waves in a homogeneously and finitely deformed layered half-space of an incompressible non-conducting magnetoelastic material in the presence of an initial uniform magnetic field is analyzed. The equations and boundary conditions governing linearized incremental motions superimposed on an underlying deformation and magnetic field for a magnetoelastic material are summarized and then specialized to a form appropriate for the study of Love-type waves in a layered half-space. The wave propagation problem is then analyzed for different directions of the initial magnetic field for two different magnetoelastic energy functions, which are generalizations of the standard neo-Hookean and Mooney–Rivlin elasticity models. The resulting wave speed characteristics in general depend significantly on the initial magnetic field as well as on the initial finite deformation, and the results are illustrated graphically for different combinations of these parameters. In the absence of a layer, shear horizontal surface waves do not exist in a purely elastic material, but the presence of a magnetic field normal to the sagittal plane makes such waves possible, these being analogous to Bleustein–Gulyaev waves in piezoelectric materials. Such waves are discussed briefly at the end of the paper

Development of magnetorheological elastomers (MREs) for strength and fatigue resistance

Natural rubber (NR)-based magnetorheological elastomers (MREs) exhibiting a reasonable switching effect were fabricated and tested. They were strong enough for use in automotive applications but still needed protection against ageing. Ethylene–propylene–diene rubber (EPDM) is a cost-effective material that is frequently used in the automotive industry because of its advantageous range of properties. With these applications in mind, it was a logical progression to the development of EPDM-based MREs. Unlike strain-crystallising NR, EPDM requires reinforcement to render its tensile and fatigue strength suitable for use in most applications. While small amounts of carbon black were sufficient for the NR-based MREs, a trade-off between non-reinforcing carbonyl iron powder (CIP) and reinforcing carbon black fillers was necessary to imbue the EPDM-based MREs with reasonably good mechanical properties. With a limit on the quantities of fillers that could be added, attention was turned to the matrix material itself and the blend of polymers employed in EPDM2 and EPDM3 were chosen in order to strengthen the EPDM-based MREs by enhancing polymer molecular weight and reinforcement. However, an unwanted effect of the stronger polymer network was the high-viscosity matrix in these compounds which hindered the alignment of magnetic particles early in the vulcanisation process. This led to poorer magnetic particle orientation, resulting in a more homogenous dispersion of the CIP and consequently produced MRE specimens that were more isotropic than anisotropic. Subsequently the switching effect of these materials was lower than would be obtained in MREs with a low viscosity (say, 40 MU) matrix. It was not feasible to sacrifice reinforcing carbon black in these compounds, but there are other possibilities open to the rubber compounder. An alternative means of reducing the viscosity of EPDM3 is simply to double the content of softening oil. This would have a slight but minimal negative effect on the tensile properties of the material. The addition of a small amount of retardant to delay vulcanisation and extend the time available for orientation of the magnetic particles into chains would also be beneficial. This would also reduce the modulus of the compound, but the reduction would again be negligible. As in all material design, there is a trade-off to be made in choosing the right combination of properties, but both of these changes would result in the development of an effective magnetorheological compound

Business process re-engineering & management journal

Magnetorheological elastomers (MRE) are smart materials whose modulus or mechanical performances can be controlled by an external magnetic field. In this chapter, the current research on the MRE materials fabrication, performance characterisation, modelling and applications is reviewed and discussed. Either anistropic or isotropic or MRE materials are fabricated by different curing conditions where magnetic field is applied or not. Anistropic MREs exhibit higher MR effects than isotropic MREs. Both steady-state and dynamic performances were studied through both experimental and theoretical approaches. The modelling approaches were developed to predict mechanical performances of MREs with both simple and complex structures. The sensing capabilities of MREs under different loading conditions were also investigated. The review also includes recent representative MRE applications such as adaptive tuned vibration absorbers and novel force sensors

Investigation of tensile properties of RTV Silicone based Isotropic Magnetorheological Elastomers.

Magnetorheological elastomer (MRE) consists of an elastomer matrix and a Ferro-magnetic ingredient. The mechanical properties of MR elastomers can be reversibly controlled by applying a magnetic field of suitable intensity. The current work focusses on the enhancement of tensile property of RTV (Room Temperature Vulcanization) silicone based elastomer. The influence of Carbonyl iron powder (CIP) content and magnetic field were experimentally investigated. Addition of CIP increases the tensile modulus but it reduces the percentage elongation and tensile strength making it brittle. Under the influence of magnetic field, the enhancement of tensile properties up to 20% content was linear. The behavior above 20% is observed to be non-linear. The onset of non-linear stress-strain behavior is investigated. Regression equation is developed from the experimental data relating percentage content with the mechanical properties of MRE. The developed equation predicted the behavior of 27% MRE with an error of less than 8%. Hyperelastic model developed by Yeoh was fitted to the stress-strain behavior of MRE with minimal error