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Servo Feedback Devices and Motor Sensors
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
Magnetorheological elastomers (MREs) are a relatively new class of smart materials that can undergo large deformations resulting from external magnetic excitation [8.37]. As composite materials, they consist of micron- or nano-sized magnetizable particles that are embedded into a non-magnetizable polymer matrix. MREs can change their mechanical behavior in response to an external magnetic field, making them to be promising candidates in developing actuators and sensing devices, such as force, temperature, and pressure sensors. A force sensor working with MRE was designed by Li et al. [8.38] for sensing normal loading. The MRE force sensor consists of three main parts: the mechanical assembly, electrical circuit, and LED display. The mechanical design is shown in Figure 8.37. The MRE is put near the bottom of the sensor. The metal spring is pressed to provide a recovery force to the sensor. As the upper plate is screwed, the O-ring is compressed, generating a preload acting on the MRE. When the reload is larger than the critical value, the sensor would generate a normal force to the MRE. Besides the preload, the external force results in the further deformation of the MRE, and the corresponding change in the resistance of the MRE can be precisely detected. The experimental testing shows that the sensor has a good linearity relationship and repeatability between the voltage output and loading force within some range of magnetic field. The MRE with the composition (55% carbonyl iron, 20% silicon rubber, and 25% graphite powder) has the best sensing capability.
Thin laminated cylindrical shells containing magnetorheological elastomers: Buckling and vibrations
Published in Wojciech Pietraszkiewicz, Wojciech Witkowski, Shell Structures: Theory and Applications Volume 4, 2017
The use of smart materials like magnetorheological elastomers (MREs) of variable physical properties allows to design durable structures with predictable characteristics satisfying such requirements as lightness, high-specific stiffness, safety, noiselessness and high buckling resistance (Librescu & Hause 2000). The accurate predictions of the buckling load and natural frequencies are extremely important problems at the stage of designing similar laminated constructions experiencing both static and dynamic loads. In the paper, we aim to show that viscoelastic properties of MREs very sensitive to an external magnetic field may be efficiently employed to solve the above-mentioned problems.
Modelization of the coupled behavior of a magnetically hard magnetorheological elastomer
Published in Bertrand Huneau, Jean-Benoit Le Cam, Yann Marco, Erwan Verron, Constitutive Models for Rubber XI, 2019
S. Hermann, C. Espanet, P. Butaud, G. Chevallier, J.F. Manceau, L. Hirsinger
The term magnetorheological elastomer (MRE) describes a composite material which consists of magnetosensitive particles dispersed in an elastomer matrix. MRE are interesting for engineering applications because their mechanical properties can be influenced by magnetic fields. The particles can be either dispersed randomly in the matrix (isotropic MRE) or be aligned in chains (anisotropic MRE). To align the particles, the composite is cured in an external magnetic field (Rigbi and Jilkén 1983, Ginder et al. 1999). MRE can furthermore be divided in S-MRE, containing magnetically soft particles and H-MRE in which magnetically hard particles like NdFeB are present.
Magnetically tunable transparency for magnetorheological elastomer films consisting of polydimethylsiloxane and Fe3O4 nanoparticles
Published in Soft Materials, 2018
Qiushu Zhang, Bei Peng, Hui Li, Jiangtao Sun
Magnetorheological elastomers (MREs) are smart composites formed by dispersions of magnetic micro- or nano particles in a non-magnetic organic viscoelastic matrix. The mechanical properties of MREs such as elastic moduli can be properly tuned by a magnetic field. Thus, they have been used for constructing the devices to control vibration (1–4). Applying magnetic field can also induce a change in their electric properties. MREs can therefore be used as magnetically tunable electronic components (5,6). In addition, since MREs are sensitive to external stimuli such as a magnetic field, force, or temperature, they have found applications in sensors (7,8) and actuators (9). However, up to now, little effort has been devoted to the effect of magnetic field on the optical properties of MREs on a micro scale although it was observed that the structuring of magnetic particles within the polymer matrix can produce “transparency windows” (10). The research work in this area might help broaden the applications of MREs to more fields such as optical microelectromechanical systems.
Nonlinear characterization of magnetorheological elastomer-based smart device for structural seismic mitigation
Published in International Journal of Smart and Nano Materials, 2021
Yang Yu, Azadeh Noori Hoshyar, Huan Li, Guang Zhang, Weiqiang Wang
As a type of novel smart material, the magnetorheological elastomer (MRE) is composed of magnetic particles suspended in the elastomeric matrix [1–3]. Generally, two types of MRE, i.e. isotropic and anisotropic, are manufactured either without the magnetic fields or under the fields. When the external magnetic fields are applied to such materials, the material’s mechanical properties such as shear modulus, stiffness, and damping will be varied accordingly [4,5]. Due to the unique characteristic of field-dependence, the MRE has been widely utilized in the design of smart devices for various engineering applications, such as vibration absorbers, vibration isolators, sensors, and actuators [6–10].
Optimization of damping characteristics of tapered MWCNT/glass fiber reinforced composite rectangular sandwich plates: A higher-order finite element formulation
Published in Mechanics of Advanced Materials and Structures, 2023
A. N. Shankar, Apichit Maneengam, Mohammed Javeed Siddique, Ajay K. S. Singholi, Rajeshkumar Selvaraj
Composite sandwich structures are widely employed in high technology applications due to their excellent mechanical properties such as high specific rigidity and high strength-to-low-weight ratio. To enhance the strength and stiffness of the laminated composite sandwich structures, the researchers focused on the attention toward nanoparticles for the better structural performance of the sandwich structures. The material properties of the carbon nanotube (CNT) gained the attention of the scientist to work in this field and it has a wide scope in recent scenarios on all the applications. Therefore, CNTs have been incorporated into sandwich structures to enhance the stiffness and damping properties. The magnetorheological elastomer (MRE) is a type of semi-active materials whose damping characteristics can be tuned by applying magnetic fields. The dynamic performance of the composite sandwich structures are dependent on the optimal ply sequences with respect to applications. Therefore identification of the optimal ply sequences of the face layer in sandwich structures is significantly important for the designer to maximize the dynamic characteristics of the sandwich systems. Zhou and Wang [1] studied the vibrations of simply-supported sandwich beam with a softcore composed of MR elastomer part and non-MR elastomer part. It was shown that the stiffness increases by increasing magnetic flux. The stiffness of the sandwich structure has been shown to improve dramatically when using the MR elastomer patch and magnetic fields. Dwivedy et al. [2] presented the instability characteristics of the sandwich beam with MRE patch and non MRE patch. They found that the instability characteristics of the sandwich structure enhance significantly by using MR elastomer patch and applied magnetic flux. Lara-Prieto et al. [3] analyzed the vibration responses of aluminum and polyethylene terephthalate (PET) material with MRF core sandwich beam. It was reported that the damping ratio of aluminum beam was higher than PET beam. Li et al. [4] proposed MRE based vibration isolator for a vehicle seat suspension system. They showed that the prototype of the MRE isolator could increase the stiffness by three-times when the applied coil current varied from 0 to 3 A. Also, it was demonstrated that with the influence of magnetic fields, the stability of the isolator is changed, which consequently suppress the seat vibration or responses. Nayak et al. [5] investigated the vibration properties of rotating aluminum sandwich beam with MR elastomer. Also, they presented the dynamic stability regions of different arrangements of partially treated MRE sandwich beam. It was seen that the stability of the MRE sandwich beam were improved with the influence of magnetic fields, static and dynamic load, and the location and length of the MR elastomer segment.