Conventional Magnetorheological Elastomers Research Articles

Fabrication and property research of a new 3D-Printable magnetorheological elastomer (MRE)

In order to meet the growing design demands for shape and structure of magnetic functional materials, particularly Magnetorheological Elastomers (MREs), additive manufacturing technology has been introduced into MRE production. Reported works of printable MRE (p-MRE) have successfully obtained high relative magnetorheological (MR) performance comparable to traditional MRE. However, there are still few studies on p-MRE with both high relative and absolute MR effects that is required for some applications such as intelligent dampers in automotive industry. In this study, polyurethane (TPU) and carbonyl iron powder (CIP) were utilized as raw materials to formulate p-MRE with high printability and high comprehensive MR performance. Based on the fused deposition modeling (FDM) process, a printing strategy suitable for this p-MRE material was determined through experimental design (DOE). The test result showed that the comprehensive MR performance of the p-MRE sheet samples obtained through linear printing path exceeded the majority of previously reported p-MRE materials. In addition, based on the analysis of the correlation between magnetic hysteresis like effect and MR effects, a circular printing path that may be beneficial for improving MR performance was proposed and corresponding p-MRE sheet sample was printed. The test results showed that compared with the linear printing path, the circular printing path further increases the comprehensive MR effect of the sheet sample to a maximum absolute MR effect of 4.2 MPa and a maximum relative MR effect of 620 %, which is comparable to most conventional MRE materials. Additionally, a theoretical framework associating magnetic field strength and filling density was proposed to explain peculiar phenomena observed in the experiments. On the basis of previous research on MREs and filler modified elastomers, a hypothesis was proposed to link magnetic field intensity with filler density, allowing the existing theory of filler modified elastomers to be used to explain the special phenomena observed in our experiments.

Adaptive beam with elastic support based on magnetorheological elastomers for modal modulation and vibration suppression

Owing to the wide modulation capability of their magneto-induced modulus, smart structure-based magnetorheological elastomers (MREs) show great promise for vibration control in numerous engineering applications. In conventional smart structure-based MREs, however, vibration absorption or isolation is mainly used for discrete structural systems, and the requirement for vibration control in continuous structures can limit the application of vibration absorbers and isolators. Therefore, it is necessary to resolve the dynamic properties of the continuous structure to obtain modal information. In this paper, different types of smart beams with adaptive elastic support (AES)-based MREs, containing dual-end elastic support, single-end elastic support, and the combination of a fixed end and an AES at an arbitrary location, are developed to tactically influence the dynamics through magneto-mechanical coupling. A dynamic model of thin-walled beams with AES was established by using the improved Fourier series method (IFSM). The numerical results confirm that the effective suppression bandwidth of the beam with MRE-AES can be shifted as a result of the modal modulation-induced energy transfer from low to high frequencies, which requires a decreasing trend of modal amplitude at the response location as the elastic support stiffness increases. According to the modal analysis, the beams with single-end AES and dual-end AES have a decreasing trend of modal amplitude in the global location as stiffness increases. However, the modal amplitude trend of the beam with a fixed end and an AES is not monotonic at certain locations. The experimental results demonstrate that MRE-AES can effectively attenuate the acceleration responses of the beams with single-end AES and with a fixed end and an AES under harmonic excitation. The resonance peaks in the transmission remarkably shift to higher frequencies with increasing magnetic flux.

Tunable low range Gr induced magnetorheological elastomer with magnetically conductive feedback

The effect of graphite (Gr) based magnetorheological elastomer (MRE) on resistance is experimentally evaluated in this research. Isotropic and anisotropic MRE samples are prepared by utilizing Gr as a filler in MRE fabrication. The physical, rheological and resistance properties of Gr-MRE are investigated and compared to those of typical or conventional MREs without Gr. Morphological aspects of Gr-MRE are characterized by field emission scanning electron microscope (FESEM), scanning electron microscope and energy dispersive x-ray spectroscopy, while rheological properties are evaluated using a rheometer. Subsequently, the resistance properties are investigated by using the designated test-rig. Based on the resistance evaluation, a curve describing the relationship of resistance (R) under different applied forces (F) and different magnetic fields (B) are established and plotted. Moreover, it is observed that the FESEM images shows the presence of Gr fractions, which contributes to the conductivity property of MRE. It is also observed that with the addition of Gr, the rheological and conductivity properties such as the storage modulus and resistance response are improved parallel with the increment of magnetic field. It is also demonstrated that the addition of Gr in MRE can contribute to the use of force detection in sensing devices.

Porous magnetic materials based on EPDM rubber filled with carbonyl iron particles

This paper deals with a possibility to prepare porous magnetic elastomers whose mechanical behavior can be controlled by means of a magnetic field. The elastomers under investigation are based on ethylene propylene diene rubber (EPDM) filled with carbonyl iron particles. The foaming agent based on azodicarbonamide was used at 2 loading levels to control their porous character and the magneto-mechanical behavior was compared with non-porous magnetic EPDM system. The non-porous systems exhibited the highest magnetorheological efficiency even though the porous systems showed lower values of storage modulus in the inactive state. Porous systems also exhibited lower mechanical hysteresis when compared to non-porous one during single-strain measurements with increasing/decreasing magnetic field due to pores which increase a distance between particles and thus lower the strength of magnetic network created at high magnetic fields. Porous systems can be potentially utilized in applications in which conventional magnetorheological elastomers are too tough, thus, porous systems offer magnetorheological material with properties between magnetorheological fluids and solid elastomers.

Study on an improved variable stiffness tuned mass damper based on conical magnetorheological elastomer isolators

Use of a variable stiffness tuned mass damper (VSTMD) is an effective approach to reduce the dynamic responses of a structure with shifting natural frequencies. Magnetorheological elastomer (MRE) isolators can be used to build VSTMD due to their tunable stiffness by applying a magnetic field. However, conventional MRE isolators show deformation limits, huge energy consumption and uneconomic production. Focused on developing a MRE VSTMD system to improve this situation, a conical MRE isolator has been proposed and tested. Compared to conventional MRE isolators, the conical isolator shows much higher efficiency, better overall stability, greater deformability and a larger tunable range. The experimental results indicate that the prototype can provide a 46.29% increase in frequency and a 75 N control force range with a 25 W power source. The quick responding MRE VSTMD system has the potential to accurately provide the desired stiffness in two directions to achieve a better structure control.

A novel magnetorheological elastomer isolator with negative changing stiffness for vibration reduction

Magneto-rheological elastomers (MREs) have attracted notable credits in the development of smart isolators and absorbers due to their controllable stiffness and damping properties. For the purpose of mitigating unwanted structural and/or machinery vibrations, the traditional MRE-based isolators have been generally proven effective because the MR effect can increase the stiffness when the magnetic field is strengthened. This study presents a novel MRE isolator that experienced reduced stiffness when the applied current was increased. This innovative work was accomplished by applying a hybrid magnet (electromagnet and permanent magnets) onto a multilayered MRE structure. To characterise this negative changing stiffness concept, a multilayered MRE isolator with a hybrid magnet was first designed, fabricated and then tested to measure its properties. An obvious reduction of the effective stiffness and natural frequency of the proposed MRE isolator occurred when the current was continuously adjusted. This device could also work as a conventional MRE isolator as its effective stiffness and natural frequency also increased when a negative current was applied. Further testing was carried out on a one-degree-of-freedom system to assess how effectively this device could isolate vibration. In this experiment, two cases were considered; in each case, the vibration of the primary system was obviously attenuated under ON-OFF control logic, thus demonstrating the feasibility of this novel design as an alternative adaptive vibration isolator.

Dynamic Viscoelastic Behavior of Multiwalled Carbon Nanotube–Reinforced Magnetorheological (MR) Nanocomposites

AbstractThis paper introduces a novel class of three-phase magnetorheological (MR) nanocomposites reinforced with multiwalled carbon nanotubes. Microstructures of the nanocomposites are characterized with the scanning electron microscopy. The dynamic viscoelastic responses are investigated under the combined magnetic fields and dynamic mechanical loads in both compression and shear modes. Experimental data demonstrate that the three-phase nanocomposites exhibit not only higher zero-magnetic-field stiffness and damping performance than conventional MR elastomers, but also higher magnetic-field-induced increase in these dynamic properties, which confirms the superiority of the proposed MR nanocomposites over conventional MR elastomers.

An Active-damping-compensated Magnetorheological Elastomer Adaptive Tuned Vibration Absorber

This article presents the development of an active-damping-compensated magnetorheological elastomer (MRE) adaptive tuned vibration absorber (ATVA). The principle and the vibration attenuation performance of the proposed active-damping-compensated ATVA were theoretically analyzed. Based on the analysis, a prototype was designed and manufactured. Its dynamic properties and vibration attenuation performances were experimentally investigated. The experimental results demonstrated that the damping ratio of the prototype was significantly reduced by the active force. Consequently, its vibration attenuation capability was significantly improved compared with a conventional MRE ATVA.

An effective permeability model to predict field-dependent modulus of magnetorheological elastomers

Magnetorheological elastomers (MREs) are composites where magnetic particles are suspended in a non-magnetic solid or a gel-like matrix. MREs are shown to have a controllable, field-dependent shear modulus. Most of conventional MREs models are based on magnetic dipole interactions between two adjacent particles of the chain. These models can predict the field-dependent properties of MREs with simple chain-like structures. In this paper, an effective permeability model is proposed to predict the field-induced modulus of MREs. Based on the effective permeability rule and taking into account the particle’s saturation, the model is proposed to predict the mechanical performances of MREs with complex structure and components. The effectiveness of the model is justified by a designed novel MREs.