Magnetorheological Elastomer Research Articles

A new inerter-based acoustic metamaterial MRE isolator with low-frequency bandgap

Abstract Acoustic metamaterials are capable of generating vibration bandgaps at specific frequency ranges, which makes them have good applications in the field of vibration isolation. To further broaden the vibration bandgaps, both magnetorheological elastomer (MRE) and graded stiffness are employed to enhance the bandgap properties. However, lowering the vibration bandgap is usually accompanied with excessive reduction of the structure stiffness. Except for reducing the stiffness, increasing the mass of the acoustic metamaterial can also lower the bandgap. In this research, a novel inerter-based acoustic metamaterial MRE isolator (IAM-MREI) was designed and prototyped. Inerters not only can generate large equivalent mass, but also are discovered to be able to greatly lower and broaden the vibration bandgap of the IAM-MREI with a brand-new mechanism, which cannot be achieved only with extra equivalent mass. The effects of the inerters on the overall performance of the IAM-MREI was thoroughly investigated and validated both theoretically and experimentally. The evaluation experiments confirmed that the IAM-MREI possesses a low frequency vibration bandgap and can provide great vibration isolation performance.

Effect of epoxidation level on rheological properties of epoxidized natural rubber-based magnetorheological elastomer

Epoxidized natural rubbers (ENR)are potential to be an alternative of natural rubber as matrix of magnetorheological elastomers (MREs). These ENR-based MREs offer various advantages such as excellent mechanical properties and damping characteristics that are well-suited for applications in vibration control and noise reduction devices. However, there is a paucity information in regard to the effect of different epoxidation levels on rheological properties of MRE. Therefore, the main aim of this study is to explore the influence of epoxidation level on rheological properties of MRE using commercialized ENR corresponding to ENR 25 and ENR 50. ENR-based MREs were created by blending with carbonyl iron particles (CIPs) and other additives, followed by curing at 150 °C for 30 min. The study involved producing ten MRE samples with various weight percentages of CIP (0,10,30,50 and 70 wt%). The storage modulus of ENR 50 exhibited a significant increment from 0.73 MPa to 1.04 MPa as compared to ENR 25 which caused the storage modulus to increase from 0.77 to 0.88 MPa. This showed that ENR 50-based MRE are stiffer in comparison to ENR 25-based MRE. Initial loss modulus value for ENR 50 (0.098 MPa) was lower than that of ENR 25 (0.112 MPa), consequently less energy is dissipated to surrounding for ENR 50-based MRE compare ENR 25-based MRE. The loss factor that represents damping properties showed that ENR 50 reached higher values (0.120 MPa) compared to ENR 25 (0.106 MPa). The increasing of CIPs content from 0 to 70 wt% contributed to increasing of magnetorheological effect for both ENR-based MRE where ENR 25 produced slightly higher with increment of 1.88 % to 22.6 % than ENR 50-based MRE with increment of 2.47 % to 18.18 % due to rise of magnetic forces generated from interaction of magnetic moments in magnetic domains of each CIPs. The results and analysis indicate that different levels of epoxidation in ENR have a marginal impact on the rheological properties of ENR-based MREs.

Actively tunable sandwich acoustic metamaterials with magnetorheological elastomers

Actively tunable sandwich acoustic metamaterials with magnetorheological elastomers

A facile fabrication for the magnetorheological elastomer composed of Fe particles and silicone rubber matrix

Magnetorheological elastomers (MREs), smart materials for sensors, absorbers, and dampers, have attracted great attention. Carbonyl Fe particles integrating an elastomer and additives are often seen. Nonetheless, time-consuming and complicated fabrication processes are encountered, and the carbonyl coating also deteriorates the magnetorheological (MR) effect. This study, to solve these dilemmas, worked on a facile fabrication process, while MREs show proper cyclic stability and good MR effect. The output stress is almost saturated after 30 times of compression. The absolute and relative MR effects of 1.11 MPa and 33.3 % were achieved, and the threshold value is located between 16Fe and 24Fe composites.

Development of High-Aspect-Ratio Soft Magnetic Microarrays for Magneto-Mechanical Actuation via Field-Induced Injection Molding.

Magnetorheological elastomers (MREs) are in demand in the field of high-tech microindustries and nanoindustries such as biomedical applications and soft robotics due to their exquisite magneto-sensitive response. Among various MRE applications, programmable actuators are emerging as promising soft robots because of their combined advantages of excellent flexibility and precise controllability in a magnetic system. Here, we present the development of magnetically programmable soft magnetic microarray actuators through field-induced injection molding using MREs, which consist of styrene-ethylene/butylene styrene (SEBS) elastomer and carbonyl iron powder (CIP). The ratio of the CIP/SEBS matrix was designed to maximize the CIP fraction based on a critical solids loading. Further, as part of the design of the magnetization distribution in micropillar arrays, the magnetorheological response of the molten composites was analyzed using the static and dynamic viscosity results for both the on and off magnetic states, which reflected the particle dipole interaction and subsequent particle alignment during the field-induced injection molding process. To develop a high-aspect-ratio soft magnetic microarray, X-ray lithography was applied to prepare the sacrificial molds with a height-to-width ratio of 10. The alignment of the CIP was designed to achieve a parallel magnetic direction along the micropillar columns, and consequently, the micropillar arrays successfully achieved the uniform and large bending actuation of up to approximately 81° with an applied magnetic field. This study suggests that the injection molding process offers a promising manufacturing approach to build a programmable soft magnetic microarray actuator.

Performance analysis of vertical smart isolator based on magnetorheological elastomer

ABSTRACT As one of the field-dependent smart materials whose stiffness and damping properties can change instantaneously and reversibly, magnetorheological elastomer (MRE) has been extensively utilized on base isolation for vibration reduction. However, most previous studies have focused on the shear dynamic performance of MRE isolators, and there are few reports on the vertical extrusion performance of basic isolators within construction equipment. In this paper, MRE materials with strong bearing capacity and suitable vertical stiffness were fabricated by comprehensively considering the selection of raw materials, particle ratio, and sample size. The tension-compression viscoelasticity of the prepared MRE under varying magnetic fields and strain amplitudes was experimentally evaluated using an MRE axial MR testing system. Eventually, a single-degree-of-freedom dynamic test rig for vibration isolation of equipment in buildings, which integrates a vertical isolator with MRE as the core component, was constructed to perform a series of experimental investigations on the alterable frequency vibration capability of the designed MRE vertical isolator. The test results reveal that the controllable stiffness-damping properties of the prepared MRE in the axial tension-compression mode can enable the developed vertical isolator to exhibit superior frequency shifting and vibration attenuating characteristics in structural vibration.

Identification of stiffness and damping characteristics of magnetorheological elastomers due to immersion in seawater

ABSTRACT Magnetorheological elastomer (MRE) materials are commonly used as vibration dampers in offshore structures. Therefore, it is urgent to investigate the degradation of this smart material because of seawater interaction. This work focuses on the immersion of MRE material in seawater, which alters its rheological and mechanical characteristics. Hence, it is important to investigate the impact of seawater immersion on the rheological characteristics of substances. This study contributes to the assessment of the stiffness and damping characteristics of MRE materials after exposure to seawater for one year. The MRE samples comprise MRE with a silicone matrix devoid of any Carbonyl Iron Particle (CIP) and MRE with 70% CIP, exhibiting both isotropic and anisotropic properties. Immersing the subject in seawater was carried out for one year. The study involved doing multiple tests, such as scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and rheological testing. The findings indicated that the samples underwent harm, erosion, and deterioration of their rheological characteristics during immersion. The stiffness values for isotropic MRE and anisotropic MRE decreased by 97% and 11%, respectively. Meanwhile, the deterioration of the damping characteristics values of isotropic MRE and anisotropic MRE was 96% and 14%, respectively.

Delamination and thrust force mitigation during drilling of unidirectional carbon fibre-reinforced plastic laminate using magnetorheological elastomer

Abstract In new improvements to the aviation industry, carbon fibre-reinforced plastic (CFRP) is a buoyant material due to its noteworthy and application-friendly properties. The behaviour of transversely isotropic CFRP, which prompts drilling-induced delamination, causes critical damage that leads to the rejection of the final product. The cause of the delamination damage is the thrust force generated by the drilling tool during the machining operation. The present work proposes an indigenous approach to suppress delamination significantly using magnetorheological elastomer (MRE). The thrust force generated by the drilling tool is recorded for varying magnetic field strengths. Delamination damage was computed using the MATLAB script. Meanwhile, specific focus was given to studying the interlaminar mechanics of a drilled hole through scanning electron microscopy. The results show that nearly 45% of the thrust force is reduced using this MRE at a maximum field strength of 0.4T compared to a conventional one. The results are further supported by a 22% and 30% smoothening of the delamination at the hole’s entry and exit, respectively. Thus, this approach helps to reduce delamination during drilling.

Study of the properties and joint operation of resonant sound absorbers depending on their geometry and relative position

The research presented in the work focuses on a damper that utilizes an "intelligent" material called multilayer magnetorheological elastomer. These devices are of interest due to their ability to adjust the elastic properties, size, and shape of the working body by manipulating the external magnetic field. They also have a high load capacity. The effectiveness of the damper's vibration isolation is determined by its design, manufacturing technology, and the composition of the multilayer magnetorheological elastomer. The mechanical and magnetic hysteresis of the device allows for evaluating the controllability of the damper and its ability to absorb vibrations. Research results indicate the presence of a symmetric and narrow hysteresis loop, not exceeding 7 μm, within the operating range of control currents.

Magnetorheological metamaterials for active broadband tuning of vibration attenuation

We propose a class of magnetorheological metamaterial plates with tunable band gaps achieved by means of a frequency-feedback control law. This approach allows for the intelligent tracking of excitation frequencies that enables an active control of band gap bounds. The active control mechanism is implemented through intelligent local resonators integrated into a main structure which comprise a mass and a magnetorheological elastomer (MRE) sensitive to an external magnetic field. The influence of the external magnetic field on vibration attenuation is examined using the Galerkin method. Next, a closed-loop frequency feedback control strategy is employed to dynamically adjust the band gap in response to excitation frequencies. This strategy significantly broadens the effective band gap range of the metamaterial plate. Besides, we studied the effect of MRE damping on broadband vibration reduction, underscoring its pivotal role in the band gap control for our magnetorheological metamaterials.

Anomalous transient conductivity of magnetic elastomer under the action of strain and magnetic field

Abstract Magnetoactive (aka magnetorheological) elastomer composites, which are elastic polymer matrices filled with micron-sized particles of a ferromagnet, are a novel type of magnetically controllable material. In addition to their complex magnetomechanical behavior, magnetoactive elastomers, as conducting substances, possess electrical resistivity that is highly sensitive to both mechanical stress and the applied magnetic field. Here, we present a study on the response of such composites to pulse mechanical or magnetic perturbations. Remarkably, a transient electric process induced by any of those stimuli is always non-monotonic. The electric current measurements reveal that before settling at the new equilibrium level, the resistivity always undergoes a substantial jump-up independently on the sign of the perturbation: a pressure on/off or the field on/off. The main goal of the work is to register the encountered effect in detail.

Single-layer iron network microstructure magnetorheological elastomer for transparent soft actuator

The motion of a soft magnetic magnetorheological elastomer, a composite material consisting of soft magnetic fillers and an elastomeric matrix, is limited by the gradient of the applied magnetic field, making its application as an out-of-plane soft actuator difficult. In this study, an anisotropic soft magnetic magnetorheological elastomer-based transparent soft actuator with large out-of-plane deformation was fabricated using a very low concentration (1 vol%) of carbonyl iron particles as the soft magnetic fillers. An applied AC electric field treatment method was used to manipulate iron particles in silicone oil, assembling and depositing them onto a glass substrate to form a single-layer iron-network microstructure. A single-layer iron-network microstructure-based magnetorheological elastomer (SL-sMRE) film with initial self-buckling was fabricated by exploiting the swelling properties of the residual silicone oil and polydimethylsiloxane. The SL-sMRE film exhibited out-of-plane deformation with a very short reaction time (228 ms) under a uniform magnetic field. When stimulated by a non-uniform magnetic field, the SL-sMRE film deformed away from the permanent magnet, which was not possible with an isotropic film. An optically transparent SL-sMRE film was applied to a transparent flexible gripping device that could detect the surface of a gripped object in real time.

A Pressure Sensor Based on the Interaction between a Hard Magnet Magnetorheological Elastomer and a Hall Effect Structure

In this article, we report a novel pressure sensing method based on the Hall effect and a hard magnet magnetorheological elastomer (hmMRE). The elastic property of the MRE under pressure was used to generate spatial variation in the magnetic flux density around the MRE, and the variation was detected by the Hall effect device underneath. As the first development in this kind of pressure sensing mechanism, we conducted research for the following three purposes: (1) to verify the Hall effect on the output signal, (2) to understand the sensor output variations under different modes of operation, and (3) to utilize the mechanism as a pressure sensor. We characterized the sensor with its operation parameters, such as signal polarity switching depending on wiring directions, signal amplitude, and offset shift depending on the input voltage. Based on the analyses, we concluded that the Hall voltage represents the pressure applied on the hmMRE, and the new pressure sensing mechanism was devised successfully.

Elaboration and Identification of the Mechanical Properties of Magnetorheological Elastomer in Frequency-temperature Dependence

Elaboration and Identification of the Mechanical Properties of Magnetorheological Elastomer in Frequency-temperature Dependence

Mechanical properties of silicone polymer with magnetic filler in magnetic field

Purpose. To investigate the change in the mechanical properties of a magnetorheological silicone elastomer consisting of a polymer filled with magnetite nanoparticles under the influence of an inhomogeneous magnetic field of an electromagnet. Methods. The experiments were carried out on a magnetic response research facility developed and manufactured independently based on known methods. The value of the deflection angle of the magnetically active receiver was determined by the optical method. Two-component silicone rubbers filled with magnetite particles were studied as samples. The manufactured samples differed in geometric dimensions, magnetic phase concentrations of 1%, 5%, 10% and 20%, and polymerization mechanism. The source of the magnetic field was electromagnets of various sizes connected to power sources. The images were captured using a Micmed 5.0 digital USB microscope.Results. The analysis of the structure of the manufactured magnetorheological silicone elastomers was carried out, as well as studies of the effect of the magnetic field strength and sample parameters on the deflection angle of the magnetically active cantilever. A theoretical interpretation of the obtained results is proposed.Conclusion. The experimental dependence of the tilt angle of a magnetically active polymer cantilever on the equilibrium position relative to the magnitude of the magnetic field strength of the electromagnet is determined. The obtained research results can be used to develop actuators and magnetoactive sensors.

A modified parametric model to predict visco-elastic properties of magneto-rheological elastomers at non-LVE region

The magneto-rheological elastomer is mostly used in vibration isolation, for which higher modulus and lower Payne effect factors are crucial parameters. Strain amplitudes and frequencies influence many applications under dynamic modes. In this work, the dynamic viscoelastic properties of MRE, fabricated using electrolyte iron (EI) particles, were measured for varying strain amplitude, magnetic field and frequency. A fractional Kelvin-Voigt (KV) model is used in a frequency region from 0.01 to 40 Hz to predict the rheological behaviour. However, the available models failed to explain the observed behaviour at low frequencies and high magnetic fields and increasing strain amplitude (i.e. in the non-viscoelastic region). Therefore, a new modified KV model is proposed in this work to incorporate the drawbacks and hence can validate for varying frequency, magnetic field and strain amplitudes. The added terms can also be used in the fractional derivative Maxwell model to explain the effect of strain amplitude and magnetic field at various frequencies. The proposed model significantly improves the quality of experimental prediction in the low-frequency range, corresponding to a slow dissipative process at different strain amplitudes.

Preparation and performance study of silicon modified polyurethane-based magnetorheological elastomeric polishing pad

Abstract By employing Magnetorheological Elastomers (MREs) as polishing pads for chemical mechanical polishing (CMP), the magnetorheological properties are utilized to effectively control the flexible removal of materials in CMP. This study presents a method for preparing a Silicon modified Polyurethane (SPU)-based MRE polishing pad, aimed at demonstrating improved magnetorheological properties while preserving mechanical properties. The SPU-based MRE polishing pad was synthesized through the copolymerization of hydroxypropyl silicone oil and polyurethane prepolymers, with subsequent evaluation of its mechanical properties and polishing performance. Fourier Transform Infrared (FTIR) analysis confirmed the successful incorporation of the soft polydimethylsiloxane main chain from organosilicon into the polyurethane main chain, forming a soft segment that intertwines with the polyurethane main chain to create a soft-hard segment crosslinked structure. Comparison to Polyurethane (PU)-based MRE, SPU exhibits significantly reduced hardness but improved wear resistance, as well as enhanced resistance to acid and alkali corrosion. Due to the presence of a soft matrix, SPU shows better magnetorheological effects than PU-based MRE. Under a magnetic field intensity of 845 mT, the magnetorheological effect of PU-based MRE is only 18%, while Si-15.96 and Si-16.79 SPU-based MREs can reach 84% and 110%, respectively. Although the Material Removal Rate (MRR) of single-crystal SiC decreases after polishing with SPU compared to PU-based MRE, a higher surface quality is achieved, and the glazing degree of the polishing pad is significantly reduced. In the magnetic field-assisted polishing of single crystal SiC, the MRR increased by 38.4% when polished with an SPU-based MRE polishing pad, whereas the MRR was only 8.7% when polished with a PU-based MRE polishing pad. This study provides further evidence for the development and application of MRE in CMP.

Magneto-sensitive elastomers – materials, fabrication, and characterisation: state of the art

Magnetorheological elastomers (MREs) are a type of material that can be altered by applying an external magnetic field due to their elastic nature. MREs are often created by combining micron-sized magnetic particles into matrices that resemble non-magnetic rubber. This review study analyses the materials, preparation processes, investigation models and application of MREs. The initial phase involves incorporating various elastic-like matrices and magnetic particles for the production of MREs, along with the corresponding preparation methods. Secondly, several examples of MRE microstructures are provided, along with various characterisation methods. The experimental demonstration shows the development of the observable mechanical features of MREs influenced by an external magnetic field. Moreover, it addresses the challenges of MREs and their applications in design domains and speculates on their potential usage.

Enhancement of rider comfort by magnetorheological elastomer based damping treatment at strategic locations of an electric two wheeler

The vibrations generated in the two-wheeled vehicles like motorcycles due to road irregularities such as cracks, potholes, and bumps on the road cause discomfort for the rider as well as the pillion. These vibrations are reported to cause lower back pains, musculoskeletal effects, fatigue, and long-term health issues. Particularly, electric two-wheelers are more susceptible to these vibrations caused by the road and need attention. This paper presents an innovative technique for the reduction of vibrations at prominent locations in the electric two-wheeler to improve the rider’s comfort. All measured accelerations are about vertical direction (along z-axis as per ISO 2631-1 standard). Passive and Semi-active damping treatments namely, Room temperature vulcanizing Silicone rubber and Magnetorheological elastomer (MRE) were applied on the test vehicle at strategic locations of vibration. Both were compared for their effectiveness in reducing the vibrations. Results showed that MRE based damping technique proved better vibration isolation at the strategic locations. The weighted root mean square acceleration as well as vibration dose values were found to decrease with the help of damping treatments thus improving the rider’s overall comfort level.

Development of pre-magnetized magnetorheological elastomer for bidirectionally variable stiffness applications

Development of pre-magnetized magnetorheological elastomer for bidirectionally variable stiffness applications