Parameter optimization of anisotropic polarization in magnetorheological elastomers for enhanced impact absorption capability using the Taguchi method

A Magnetorheological Elastomer (MRE) can be categorized as a smart material as it can respond when it is subjected to a magnetic field against itself. Shrinking and changing shape in MRE is due to the displacement of magnetic particle in the MRE matrix. However, the lack of understanding of the magnetic flow through magnetic particle in the elastomer matrix causes difficulties to improve the best MRE matrix type and a magnetic circuit for use in MRE devices. In this paper, a finite element magnetic method (FEMM) software has been used to investigate and to study the effect of the magnetic flow when the angle of the magnetic particle in the MRE changed. The analysis was conducted in two-dimensional cross-section (axisymmetric type) with two magnetic particles in the elastomer matrix and the magnetic core. The result shows by changing the angle of the magnetic particle, the value of the magnetic flow and magnetic flux density also change. As a conclusion, the magnetic particle arrangement in the elastomer matrix plays a vital role in designing the MRE matrix layer and MRE device. By understanding the magnetic flow through the magnetic particle, one can improve the method in the preparation of MRE matrix and MRE magnetics circuit.

Modified silane-coated carbonyl iron/natural rubber composite elastomer and its magnetorheological performance

Soft hybrid magnetorheological elastomer: Gap bridging between MR fluid and MR elastomer

In this study, the vibration analysis of sandwich rectangular plates with magnetorheological (MR) elastomer damping treatment is presented. The rectangular plate is combined with a magnetorheological elastomer core layer and a constraining layer to improve the vibration behaviors of the sandwich system. The MR material shows variations in the rheological properties when subjected to varying magnetic fields. Additionally, the MR material exhibits a rapid time response and is applicable to structures or devices when a tunable system is required. The magnetorheological elastomer is found to have a significant effect on the vibration characteristics of the sandwich rectangular plate. The modal damper and the natural frequencies for the sandwich plate system are calculated for various magnetic fields and some designed parameters by utilizing the finite element method. The damping effects of the sandwich plate system can be controlled and changed when different magnetic field strengths are applied.

In this study, anisotropic magnetorheological elastomers with 0% and 15% weight fractions of silicone oil were fabricated under a magnetic field that was rotated with a 45° angle so that the iron particle alignment inside the magnetorheological elastomer was 45° to the direction of flat magnetorheological elastomer. Scanning electron microscopic images confirmed the aligned structure of iron particles and showed that the sample with 15% silicone oil contribution resulted in a less volume fraction of iron particles. The magnetorheological elastomers were then tested in an oscillatory pure shear mode at different shear strain amplitudes under different magnetic flux densities to measure their dynamic viscoelastic properties. The testing results showed that the magnetorheological elastomer with 15% silicone oil had lower zero-field storage and loss moduli and also had higher maximum magnetorheological effect than the magnetorheological elastomer with 0% silicone oil. Because of the 45° iron particle alignment, the storage modulus of the magnetorheological elastomers had a higher value in a particular direction than its contrary direction. These unique properties made the magnetorheological elastomers with 45° iron particle alignment to be potentially used in industry where extra support is needed in a particular direction.

Magnetorheological elastomer (MRE) is an intelligent composite material and has been widely used in various fields such as vibration reduction and sensing. MRE has an excellent magnetorheological effect through the chaining of its internal magnetic particles. Current studies on MREs mainly focus on the preparation of materials and characterization of mechanical properties. However, very few studies have been conducted on the mechanism of magnetic particle motion during MRE curing. Based on the silicone rubber‐based MRE, the motion mechanism of magnetic particles during curing was explored through numerical simulation. First, we analyzed the magnetic force and viscous force of magnetic particles in MRE and discussed the equations of motion of magnetic particles under applied magnetic field. Further, we established a uniform magnetic field model through the finite element method and simulated the motion of two magnetic particles under the magnetic field. Finally, we discussed the effects of particle distribution angles, particle radii, applied magnetic field strength, and distance between particles on particle velocity and displacement. The results show that the distance between particles has the greatest influence on the motion of magnetic particles, and the size of the distance between particles will affect the contact time of the particles, thus affecting the chain formation of magnetic particles in the MRE.

In this study, 3D printed magnetorheological (MR) elastomer has been characterized through a force vibration testing. The 3D printed MR elastomer is a composite consisting three different materials, magnetic particles and two different elastomers. The MR elastomers were printed layer-by-layer by encapsulating MR fluid within the polymeric elastomer and then allowed to cure at room temperature. The 3D printing allowed to print various patterns of magnetic particles within the elastomeric matrix. In the presence of an external magnetic field, both elastic and damping properties of the 3D printed MR elastomers were changed. Natural frequency, stiffness, damping ratio, damping coefficient, and shear modulus were increased with increasing magnetic field. For the single degree-of-freedoms system, shear mode MR elastomers suppressed the transmitted vibration amplitude up to 31.4% when the magnetic field was 550 mT. The results showed that the 3D printed MR elastomer could be used as a tunable spring element for vibration absorption or isolation applications. However, further optimization of the magnetic particles’ configurations should be performed to obtain the higher MR effect.

Magnetorheological elastomer (MRE) consists of magnetic particles known as carbonyl iron (CIPs), which have been locked in a silicone-based matrix, in various alignments. However, current MRE exhibits inadequate rheological properties due to several issues such as particle alignments. Therefore, in this study, a new approach of the particle alignment of CIPs in MRE, namely fountain-like structure, is introduced. It is expected that this kind of MRE exhibits enhancement rheological responses, in off- and on-state conditions. This work includes the development of a new mold that can produce various directions of magnetic flux lines in order to have fountain-like structures of CIPs in MRE, during the curing process. Three types of particle alignments in MRE, namely isotropic, fountain-like and inverted fountain-like, are fabricated. The rheological properties of MRE in terms of storage modulus and MR effect are measured in an oscillatory shear mode using a rheometer. The results have revealed that fountain-like MRE exhibits higher storage modulus than the isotropic MRE, approximately 0.6 MPa of increment in the strain sweep test, in an on-state condition. Furthermore, it has been demonstrated from strain, frequency and the current sweep test that the rheological properties of fountain-like MRE related to storage modulus and magnetorheological (MR) effect are higher compared to the inverted fountain-like MRE.

Magnetorheological Elastomers (MREs) belong to a family of so-called smart materials which consist of micron sized magnetically permeable particles suspended in a non-magnetic medium (Boczkowska et al. 2007). Upon application of a magnetic field, the rheological properties of these materials are rapidly and reversibly altered (Lokander & Stenberg 2004). Various elastomers such as silicone rubber (Lockette et al. 2008, Farshad & Benine 2004), natural rubber (Chen et al. 2007) and polyurethane (Boczkowska et al. 2009) have been used as the rubber matrix to produce MREs with different properties. MREs can be fabricated either in the absence of, or in the presence of a magnetic field during the curing process. The former technique results in isotropic or homogenous MREs (Gong et al. 2005, Lokander & Stenberg 2003) while the latter results in anisotropic MREs with particles aligned into chain-like and columnar structures parallel to the direction of the applied field (Zhang et al. 2010).

Magnetorheological elastomer (MRE)-based base isolation system has been proposed to compensate for the drawbacks of the existing passive-type base isolation system. MRE is one of smart material with magnetorheological (MR) effect that can change the stiffness and damping ratio in real time when the magnetic field is applied. The conventional MREbased base isolation system has inter-place between MRE and electromagnetic system. This is determined in consideration of the deformation of MRE, resulting in loss of magnetic flux density and excessive volume of MRE-based base isolation system. Since the strain of the MRE should be considered to be 100 % as base isolation system, the size of the base isolation system becomes large and the practical applicability is remarkably reduced. In addition, the loss of the magnetic flux density increases according to the size of the inter-space between MRE and electromagnetic system. Therefore, a new type of electromagnetic system is proposed to address these problems. In this study, an electromagnetic system which can move with MRE by separating it to the laminated type is proposed. MRE-based base isolation system with the laminated electromagnetic system occupies a small volume compared to the conventional MRE-based base isolation system and can form magnetic closed loop which can minimize the loss of the magnetic flux density. The numerical simulation was performed to compare the proposed electromagnetic system and the conventional MRE-based base isolation. From the numerical simulation, the lab-scale experiment was carried out and the proposed method can be utilized to improve the reality of MRE-based base isolation system.

Magnetorheological elastomer (MRE) is a novel kind of magnetorheological materials and has been successfully used to control the structure vibration due to its property of variable stiffness under different magnetic field. In order to improve the properties of MRE, it urgently needs to investigate the preparation methods of MRE and build a corresponding test system to evaluate the performance of MRE in different operating modes. In this paper, different magnetic devices for preparing MRE were studied and designed, and the material was fabricated by the permanent magnets with additional permeability equipment at last. Then, according to the SDOF principle, a novel test system was built in order to investigate the mechanical properties of MRE, and exact close-form expressions of the stiffness, loss factor and other mechanical parameters of MRE, under different magnetic field, have been calculated to analyze the properties of MRE.

A novel lateral vibration isolator utilizing magnetorheo logical elastomers (MREs) with the field-dependent d amping and stiffness was proposed in order to improve the adaptive performance. First, soft silicone rubber MREs with a highlyadjustable shear storage mo dulus was fabricated. Then , the lateral MREs isolator was dev eloped with a uniqu e laminated structure of MRE layers and steel p lates, which enables to withstand larg e vertical loads and adapts to the situation of large lateral displacement. Also, the electromagnetic analysis and design employed electromagnetic finite element method (FEM) to optimize magnetic circuit inside the proposed device. To evaluate the effectiveness of the lateral MREs isolator, a series of experimental tests were carried o ut und er variou s app lied magnetic fields. Experimental results show that the proposed MREs isolato r can triumphantly change the lateral stiffness and eq uivalent damping up to 140% and 125%, respectively. This work demo nstrates the performance of the designed lateral MREs isolator and itscapacity in vibration mitigation for the complex situation. Keywords: Magnetorheological elastomers, finite element method, isolator, vibration mitigation

This paper presents a numerical investigation of a smart base isolation system employing magneto-rheological (MR) elastomers or an MR elastomer-based base isolation system. MR elastomers are a new class of smart materials whose elastic modulus or stiffness can be adjusted depending on the magnitude of the applied magnetic field. Hence, they can be used as controllable stiffness elements in engineering systems. The primary goal of this study is to investigate the dynamic performance of the smart base-isolation in mitigating excessive vibrations of a building structure under earthquake loadings. To this end, a five-story shear building model coupled with a smart base-isolation is developed. Using this model, a series of numerical simulations is performed to evaluate the effectiveness of the MR elastomer-based base isolation system under several historic seismic excitations. The results show that the proposed base isolation system outperform the conventional passive-type base isolation system in reducing the responses of the building structure for all seismic excitations considered in this study.

The magneto-thermo-elastic steady shear behaviors of isotropic smart composites of silicon rubber matrix randomly filled with ferromagnetic particles, commonly referred to as magnetorheological (MR) elastomers, are investigated experimentally and theoretically in the present study. The strip specimens of the MR elastomer composite with different ferromagnetic particle concentrations are fabricated and implemented for lap-shear tests under both magnetic and thermal fields. It is illustrated that the magneto-thermo-elastic shear modulus of the MR elastomer is markedly enhanced with the volume fraction of ferromagnetic particles and the applied external magnetic field, while the shear modulus is decreased with the environment temperature. To qualitatively elucidate the magneto-thermo-elastic shear performance of this kind of magnetic smart composites, a modified constitutive of hyperelasticity is suggested taking into account the influence of magnetic field and temperature on the magnetic potential energy and strain energy. The theoretical modeling predictions on the stress–strain behaviors for different applied magnetic fields and environment temperatures are compared to experimental observations to demonstrate a good agreement.

The linear viscoelastic behaviour of magnetorheological elastomers is analysed in this work according to their formulation and working conditions. This study comprised both the synthesis of different magnetorheological elastomers and the strain and frequency sweep characterization under different magnetic fields and temperatures. The characterization was performed by a Physica MCR 501 rheometer from Anton Paar, equipped with a magnetorheologic cell 70/1T MRD. In the synthesis with a given elastomeric matrix, samples with different magnetic particle content are studied with two types of curing conditions: under the action of a magnetic field (anisotropic magnetorheological elastomers) and without a magnetic field (isotropic magnetorheological elastomers). The working conditions are excitation frequency, temperature and the applied external magnetic field. In this work, a new procedure to determine the linear viscoelastic behaviour is proposed; the loss factor is analysed in addition to analysing the storage modulus to determine the linear viscoelastic region of each sample. The results show that high temperatures and magnetorheological elastomers with higher volume fraction of magnetic particles restrict the linear viscoelastic behaviour of magnetorheological elastomers.