A state-of-the-art review on magnetorheological elastomer devices

© 2014 IOP Publishing Ltd. During the last few decades, magnetorheological (MR) elastomers have attracted a significant amount of attention for their enormous potential in engineering applications. Because they are a solid counterpart to MR fluids, MR elastomers exhibit a unique field-dependent material property when exposed to a magnetic field, and they overcome major issues faced in magnetorheological fluids, e.g. the deposition of iron particles, sealing problems and environmental contamination. Such advantages offer great potential for designing intelligent devices to be used in various engineering fields, especially in fields that involve vibration reduction and isolation. This paper presents a state of the art review on the recent progress of MR elastomer technology, with special emphasis on the research and development of MR elastomer devices and their applications. To keep the integrity of the knowledge, this review includes a brief introduction of MR elastomer materials and follows with a discussion of critical issues involved in designing magnetorheological elastomer devices, i.e. operation modes, coil placements and principle fundamentals. A comprehensive review has been presented on the research and development of MR elastomer devices, including vibration absorbers, vibration isolators, base isolators, sensing devices, and so on. A summary of the research on the modeling mechanical behavior for both the material and the devices is presented. Finally, the challenges and the potential facing magnetorheological elastomer technology are discussed, and suggestions have been made based on the authors' knowledge and experience

A novel phenomenological model for dynamic behavior of magnetorheological elastomers in tension-compression mode

Tension-compression operation in MR elastomers (MREs) offers both the most compact design and superior stiffness in many vertical load-bearing applications, such as MRE bearing isolators in bridges and buildings, suspension systems and engine mounts in cars, and vibration control equipment. It suffers, however, from lack of good computational models to predict device performance, and as a result shear-mode MREs are widely used in the industry, despite their low stiffness and load-bearing capacity. We start with a comprehensive review of modeling of MREs and their dynamic characteristics, showing previous studies have mostly focused on dynamic behavior of MREs in shear mode, though the MRE strength and MR effect are greatly decreased at high strain amplitudes, due to increasing distance between the magnetic particles. Moreover, the characteristic parameters of the current models assume either frequency, or strain, or magnetic field are constant; hence, new model parameters must be recalculated for new loading conditions. This is an experimentally time consuming and computationally expensive task, and no models capture the full dynamic behavior of the MREs at all loading conditions. In this study, we present an experimental setup to test MREs in a coupled tension-compression mode, as well as a novel phenomenological model which fully predicts the stress-strain material behavior as a function of magnetic flux density, loading frequency and strain. We use a training set of experiments to find the experimentally derived model parameters, from which can predict by interpolation the MRE behavior in a relatively large continuous range of frequency, strain and magnetic field. We also challenge the model to make extrapolating predictions and compare to additional experiments outside the training experimental data set with good agreement. Further development of this model would allow design and control of engineering structures equipped with tension-compression MREs and all the advantages they offer.We acknowledge funding from the European Research Council grant EMATTER 280078

A review on magneto-mechanical characterizations of magnetorheological elastomers

Magnetorheological elastomers (MREs) are a class of recently emerged smart materials whose moduli are largely influenced when exposed to an external magnetic field. The MREs are particulate composites, where micro-sized magnetic particles are dispersed inside a non-magnetic polymeric matrix. These elastomers are known for changing their mechanical and rheological properties in the presence of a magnetic field. This change in properties is widely known as the magnetorheological (MR) effect. The MR effect depends on a number of factors such as type of matrix materials, type, concentration and distribution of magnetic particles, use of additives, working modes, and magnetic field strength. The investigation of MREs’ mechanical properties in both off-field and on-field (i.e. the absence and presence of a magnetic field) is crucial to deploy them in real engineering applications. The common magneto-mechanical characterization experiments of MREs include static and dynamic compression, tensile, and shear tests in both off-field and on-field. This review article aims to provide a comprehensive overview of the magneto-mechanical characterizations of MREs along with brief coverage of the MRE materials and their fabrication methods

Magnetorheological Elastomers: Materials and Applications

Magnetorheological elastomers (MREs) are a type of soft magneto-active rubber-like material, whose physical or mechanical properties can be altered upon the application of a magnetic field. In general, MREs can be prepared by mixing micron-sized magnetic particles into nonmagnetic rubber-like matrices. In this chapter, the materials, the preparing methods, the analytical models, and the applications of MREs are reviewed. First, different kinds of magnetic particles and rubber-like matrices used to prepare MREs, as well as the preparing methods, will be introduced. Second, some examples of the microstructures, as well as the microstructure-based analytical models, of MREs will be shown. Moreover, the magnetic field-induced changes of the macroscopic physical or mechanical properties of MREs will be experimentally given. Third, the applications of MREs in engineering fields will be introduced and the promising applications of MREs will be forecasted. This chapter aims to bring the reader a first-meeting introduction for quickly knowing about MREs, instead of a very deep understanding of MREs

Nonlinear Characterization of the MRE Isolator Using Binary-Coded Discrete CSO and ELM

© 2018 World Scientific Publishing Company. Magnetorheological elastomer (MRE) isolator has been proved as a promising semi-active control device for structural vibration control. For its engineering application, developing an accurate and robust model is definitely necessary and also a challenging task. Most of the present models, belonging to parametric models, need to identify various model parameters and sometimes are not capable of perfectly capturing the unique characteristics of the device. In this work, a novel nonparametric model is proposed to characterize the inherent dynamics of the MRE isolator with the features of hysteresis and nonlinearity. Initially, dynamic tests are conducted to evaluate the performance of the isolator under various loading conditions, including harmonic, random, and seismic excitations. Then, on the basis of the captured experimental results, a hybrid learning method is designed to forecast the nonlinear responses of the device with known external inputs. In this method, a type of single hidden layer feed-forward network, called extreme learning machine (ELM), is developed to forecast the nonlinear responses (shear force) of the device with captured velocity, displacement, and current level. To obtain optimal performance of the developed model, an improved binary-coded discrete cat swarm optimization (BCDCSO) method is adopted to select optimal inputs and neuron number in the hidden layer for the network development. The performance of the proposed method is verified through the comparison between experimental results and model predictions. Due to the noise influence in the practical condition, the robustness of the proposed method is also validated via adding noise disturbance into the supplying currents. The results show that the proposed method outperforms the standard ELM in terms of characterization of the MRE isolator, even though the captured responses are polluted with external measurement noises

Design, Modelling and Control of an Adaptive Vibration Isolator Featuring Magnetorheological Elastomer

Magnetorheological elastomers (MREs) are smart materials whose viscoelastic properties can be varied upon the application of an external magnetic field. They are solid analogue of well-known MR fluids (MRFs) in which magnetic particles are embedded in a non-magnetic elastomer matrix instead of carrier fluids. Compared with their fluid counterparts, MREs do not have problems associated with particles' sedimentation, stability and leakage often encountered in MRFs. Besides in contrast to MRF-based adaptive devices, MRE-based systems can provide field dependent variable stiffness and damping simultaneously due to viscoelastic properties of MREs. This unique behaviour of MREs enable them to be effectively utilized in the development of adaptive isolators or absorbers to supress vibrations in wide range of frequencies. The present research study aims to provide a comprehensive investigation of the material characterization and phenomenological modelling of MREs under varying dynamic loading conditions, design and development of a novel vibration and shock isolator featuring magnetorheological elastomers, design optimization of the proposed isolator to enhance its dynamic range and finally design and implementation of semi-active control strategies to mitigate vibration and shock under different external disturbances. MREs with a 25% volume fraction of soft magnetic particles (carbonyl iron) were used to investigate variation of storage and loss moduli of MRE under varied frequencies, strain amplitudes, and magnetic field densities. Considering operation of MREs in the linear range, field dependent linear viscoelastic models based on the Kelvin–Voigt, Maxwell, Standard Linear Solid, and Generalized Maxwell models, were formulated to predict the variation of storage and loss moduli under varying driving frequency and applied magnetic flux densities. The performance of these models to capture the response behaviour of MREs under different applied frequencies and magnetic field were subsequently compared. A semi-active MRE-based vibration isolator operating under shear mode with embedded electromagnet was then proposed. Analytical magneto-static model of the magnetic circuit of the proposed adaptive isolator was first formulated using Ampere’s law to estimate the induced magnetic flux density in the MRE region gaps versus applied current to the electromagnet. The validity of the analytical results was verified using the finite element magneto-static analysis. A multidisciplinary design optimization problem was subsequently formulated to optimize the isolator geometrical parameters as design variables to maximize its frequency bandwidth under weight, material magnetic saturation, and total volume constraints. A hybrid approach based on combination of Genetic Algorithm (GA) and gradient based Sequential Quadratic Programming (SQP) was used to accurately capture the global optimal solution for the optimization problem. Finally, closed-loop control strategies, based on on-off sky-hook and PID, were implemented and compared to assess the capability of the proposed adaptive isolator to mitigate vibration and shock under different disturbances

A novel MRE adaptive seismic isolator using curvelet transform identification

Magnetorheological elastomeric (MRE) material is a novel type of material that can adap-tively change the rheological property rapidly, continuously, and reversibly when subjected to real-time external magnetic field. These new type of MRE materials can be developed by employing various schemes, for instance by mixing carbon nanotubes or acetone contents during the curing process which produces functionalized multiwall carbon nanotubes (MWCNTs). In order to study the mechanical and magnetic effects of this material, for potential application in seismic isolation, in this paper, different mathematical models of magnetorheological elastomers are analyzed and modified based on the reported studies on traditional magnetorheological elastomer. In this regard, a new feature identification method, via utilizing curvelet analysis, is proposed to make a multi-scale constituent analysis and subsequently a comparison between magnetorheological elastomer nanocomposite and traditional magnetorheological elastomers in a microscopic level. Furthermore, by using this “smart” material as the laminated core structure of an adaptive base isolation system, magnetic circuit analysis is numerically conducted for both complete and incomplete designs. Magnetic distribution of different laminated magnetorheological layers is discussed when the isolator is under compressive preloading and lateral shear loading. For a proof of concept study, a scaled building structure is established with the proposed isolation device. The dynamic performance of this isolated structure is analyzed by using a newly developed reaching law sliding mode control and Radial Basis Function (RBF) adaptive sliding mode control schemes. Transmissibility of the structural system is evaluated to assess its adaptability, controllability and nonlinearity. As the findings in this study show, it is promising that the structure can achieve its optimal and adaptive performance by designing an isolator with this adaptive material whose magnetic and mechanical properties are functionally enhanced as compared with traditional isolation devices. The adaptive control algorithm presented in this research can transiently suppress and protect the structure against non-stationary disturbances in the real time

Analysis of the magneto-thermo-dynamic behaviour of magnetorheological elastomers

Azken hamarkadetan, bibrazioen aurkako aplikazioen helburu nagusia osagaien bizitza erabilgarria, erosotasuna eta segurtasuna areagotzea izan da. Hala ere, gaur egungo aplikazioek lan-baldintza aldakorretara moldatzeko malgutasuna behar dute. Hori dela eta, material adimenduak gero eta gehiago erabiltzen ari dira industriako sektore ezberdinetan. Material talde honen barruan elastomero magnetoerreologikoak daude, eremu magnetiko baten eraginpean beraien propietateak aldatzen dituztelako. Tesi doktoral honen helburu nagusia elastomero magnetoerreologikoen propietate magnetotermiko biskoelastikoak aztertzea da, aplikazio industrialetan elastomero magnetoerreologikoen erabilpena areagotu ahal izateko. Hiru matrize ezberdin eta zortzi partikula-kontzentrazio bolumetriko erabili dira elastomero magnetoerreologiko isotropo eta anisotropoak sintetizatzean. Galerafaktorea eta metatze-modulua aztertzen dituen irizpide berria proposatu da sintetizaturiko laginen tarte biskoelastiko lineala definitzeko. Gainera, tarte honen sintesieta karakterizazio-aldagaiekiko menpekotasuna aztertu da. Tarte biskoelastiko lineala definitu ostean, sintesi- eta karakterizazio-aldagaien eragina propietate magnetobiskoelastiko linealetan aztertu dira. Horrela, material hauen atenuazio maximoaren aldakuntza definitu da. Bestalde, konpresio-entsegu magnetodinamiko berria diseinatu eta fabrikatu da, elastomero magnetoerreologikoak frekuentzia altuetan neurtu ahal izateko. Konpresioko propietateak neurtzeko prozedura definitu eta gero, elastomero magnetoerreologiko isotropoen konpresio-tarte biskoelastiko lineala aztertu da. Horrela, partikulakontzentrazioaren, frekuentziaren eta eremu magnetikoaren eragina propietate magnetobiskoelastiko linealetan definitu da. Azkenik, bi modelo magneto-biskoelastiko berri garatu dira, bata elastomero magnetoerreologiko isotropoetarako eta bestea anisotropoetarako. Bi ereduetan, bilakaera biskoelastikoa aurreikusteko lau parametroko deribatu frakzionarioen eredua erabili da. Arrhenius-en eredua erabiliz tenperaturearen eragina modelatu da, eta proposaturiko eredu biskoelastikoari gehitu zaio. Gainera, proposaturiko ereduko parametro bakoitzean partikula-kontzentrazioak duen eragina aztertu eta modelatu da. Elastomero magnetoerreologiko isotropoetan eremu magnetikoak eragiten duen modulu magneto induzitua modelatzeko, dipolo-dipolo interakzioetan oinarritua dagoen eredua garatu da. Elastomero magnetoerreologiko anisotropoei dagokienez, eremu magnetikoarekiko menpekotasuna modelatzeko material hauen permeabilitate magnetikoetan oinarritua dagoen eredua garatu da. Eredu biskoelastikoa eta eredu magnetikoa elkartuz, elastomero magnetoerreologiko anisotropoen bilakaera magnetobiskoelastikoa aurreikusten duen eredu berri bakar bat garatu da.En las últimas décadas, se han desarrollado múltiples aplicaciones anti-vibratorias con el fin de aumentar la vida útil de los componentes, el confort y la seguridad. La mayor parte de estas aplicaciones utilizan materiales que no se pueden adaptar a unas condiciones de trabajo variables, por lo que surgen como alternativa los materiales inteligentes. Dentro de éste grupo de materiales, se encuentran los elastómeros magnetorreológicos que poseen la capacidad de modificar sus propiedades cuando se aplica un campo magnético externo. El principal objetivo de ésta tesis es analizar el comportamiento magneto-térmicodinámico de los elastómeros magnetorreológicos para incrementar su uso en aplicaciones industriales. Se han sintetizado elastómeros magnetorreológicos isótropos y anisótropos con tres matrices diferentes y ocho concentraciones volumétricas de partículas. Se ha propuesto un nuevo criterio para definir el rango viscoelástico lineal de los elastómeros magnetorreológicos a cortadura analizando el factor de pérdida y el módulo de almacenamiento. Además, se ha estudiado la influencia de las variables de síntesis y de caracterización en el rango viscoelástico lineal, y en las propiedades magneto-viscoelásticas de los elastómeros magnetorreológicos isótropos y anisótropos, lo que ha permitido establecer la máxima atenuación de estos materiales. Adicionalmente, se ha diseñado e implementado un nuevo ensayo magnetodinámico de compresión para caracterizar los elastómeros magnetorreológicos a altas frecuencias. En este modo de trabajo se han establecido el límite viscoelástico lineal y las propiedades magneto-viscoelásticas en función de la concentración de partículas, frecuencia y campo magnético. Por último se han creado dos nuevos modelos magneto-viscoelásticos, uno para elastómeros magnetorreológicos isótropos y otro para anisótropos. Ambos, utilizan un modelo de derivadas fraccionarias de cuatro parámetros para describir el carácter viscoelástico, al que se ha acoplado el modelo de Arrhenius para incluir la temperatura. Cada uno de los parámetros del modelo viscoelástico se ha analizado y modelado en función de la concentración de partículas. En el modelo viscoelástico de elastómeros magnetorreológicos isótropos se ha implementado un nuevo modelo magneto-inducido basado en la interacción dipolo-dipolo para incluir el efecto del campo magnético. En cuanto a los elastómeros magnetorreológicos anisótropos, se ha desarrollado un nuevo modelo para el módulo magneto-inducido a partir de las permeabilidades magnéticas. Este modelo se acopla al efecto viscoelástico dando un único modelo magneto-viscoelástico para elastómeros magnetorreológicos anisótropos.In the last decades, many anti-vibration applications have been developed to increase the life time of components, the comfort and the security. Most of these applications are based on materials that cannot be adapted to variable working conditions, so that smart materials arise as an alternative. Within these group of materials, magnetorheological elastomers are found whose dynamic properties can be reversibly modified and controlled by an external magnetic field. The main goal of the presented dissertation was to analyse the magneto-thermodynamic behaviour of magnetorheological elastomers to enhance its use in industrial applications. Isotropic and anisotropic magnetorheological elastomers samples were synthesised with three different matrices and eight particle contents to study the shear magneto-viscoelastic properties. A new criteria analysing the loss factor and storage modulus was determined to define the shear linear viscoelastic region of magnetorheological elastomers, and the influence of synthesis and characterisation variables in the linear region was studied. Within this linear region, the magneto-viscoelastic properties of isotropic and anisotropic magnetorheological elastomers were studied, and the maximum attenuation variability of these materials was established. A new magneto-dynamic compression test was designed and manufactured, and the procedure to characterise magnetorheological elastomers at high frequencies in compression mode was implemented. Furthermore, the linear viscoelastic region was defined in these working mode, and the magneto-dynamic properties were analysed as a function of the particle content, the frequency and the magnetic field. Finally, two new magneto-viscoelastic models were developed, one for isotropic and another one for anisotropic magnetorheological elastomers. In both models, the viscoelastic nature was modelled using a four-parameter fractional derivative model, and the influence of temperature was introduced using the Arrhenius model. Moreover, the influence of particle content in each parameter was analysed and modelled, and a new magneto-induced modulus model based on the dipole-dipole interactions was coupled with the developed models for isotropic magnetorheological elastomers. In respect of anisotropic magnetorheological elastomers, a new magnetoinduced modulus model was developed using magnetic permeability components, and it was coupled to the viscoelastic effect in a single magneto-viscoelastic model for anisotropic magnetorheological elastomers

Development of adaptive seismic isolators for ultimate seismic protection of civil structures

Base isolation is the most popular seismic protection technique for civil engineering structures. However, research has revealed that the traditional base isolation system due to its passive nature is vulnerable to two kinds of earthquakes, i.e. the near-fault and far-fault earthquakes. A great deal of effort has been dedicated to improve the performance of the traditional base isolation system for these two types of earthquakes. This paper presents a recent research breakthrough on the development of a novel adaptive seismic isolation system as the quest for ultimate protection for civil structures, utilizing the field-dependent property of the magnetorheological elastomer (MRE). A novel adaptive seismic isolator was developed as the key element to form smart seismic isolation system. The novel isolator contains unique laminated structure of steel and MR elastomer layers, which enable its large-scale civil engineering applications, and a solenoid to provide sufficient and uniform magnetic field for energizing the field-dependent property of MR elastomers. With the controllable shear modulus/damping of the MR elastomer, the developed adaptive seismic isolator possesses a controllable lateral stiffness while maintaining adequate vertical loading capacity. In this paper, a comprehensive review on the development of the adaptive seismic isolator is present including designs, analysis and testing of two prototypical adaptive seismic isolators utilizing two different MRE materials. Experimental results show that the first prototypical MRE seismic isolator can provide stiffness increase up to 37.49%, while the second prototypical MRE seismic isolator provides amazing increase of lateral stiffness up to 1630%. Such range of increase of the controllable stiffness of the seismic isolator makes it highly practical for developing new adaptive base isolation system utilizing either semi-active or smart passive controls. © 2013 SPIE

Shock isolation using magnetorheologically responsive technology

The purpose of this thesis is to develop a shock isolation system using magnetorheologically (MR) responsive technology to isolate shock input to various components in the light weight military vehicles susceptible to ballistic shock effects; Two methods are chosen for isolation of the shock. One is the friction damper based on MR fluid and the other is an elastomer based on magnetically responsive elastomer (MRE). Both approaches can be utilized for semi-active control schemes that have been widely used because of its unique feature of using variable damping and stiffness characteristics of the isolator; In this thesis, both computer simulation and experimental verification are presented to show the effectiveness of the technologies in isolating the shock and the performance is evaluated by the comparison with the passive isolator as a baseline