Magnetorheological Elastomer Material 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.

A Comparative Study on Various ANN Optimization Algorithms for Magnetorheological Elastomer Carbonyl Iron Particle Concentration Estimation

Estimation particle composition such as particle shape, size, and concentration are crucial prior to the fabrication process of magnetorheological elastomer (MRE) to avoid process repetition due to inaccurate formulation. Currently, most of MRE prediction model were purposely used to predict the rheological properties such as shear stress and dynamic modulus, known as forward model. Nonetheless, very few studies have been reported to be capable able of predicting particle composition particularly in MR materials, which known as inverse model. Therefore, this paper proposed a carbonyl iron particle (CIP) concentration based MRE prediction model using neural network algorithm. Neural network-based machine learning model is more approachable compared to conventional mathematical modelling approach due to easily identify trends and pattern while handling multi-variety data. Various optimization algorithms have been employed such as Adam, RMSprop, SGD, AdaGrad, and Nadam throughout the modelling process. As the results, given shear strain amplitude, magnetic flux density, storage modulus, and loss factor as model input, SGD gave the maximum prediction accuracy with 0.95 and 3.038 MPa of R2 and RMSE, respectively. Hence, this model can be the basis to the MRE material and devices development particularly as the tool to reduce costing and time consuming.

Vibration analysis of a rotor-bearing system using magneto-rheological elastomers

Magneto rheological materials are considered as a promising adaptive means of vibration control. This paper proposes a new configuration of smart bearings comprising magneto-rheological elastomer (MRE) layer inserted between the bearing pedestal and the foundation. This configuration provides a directional vibration controllability in both horizontal and vertical directions of a rotor-bearing system. The effect of using MRE layer on the vibration response and the resonant speeds of a rotor-bearing system is investigated. The finite element method is used to derive a dynamic model for the rotor-bearing system using shaft elements based on the Rayleigh beam theory and accounting for the gyroscopic effect and internal damping of the shaft. Simulation results reveal that the use of MRE materials in passive mode leads to downshifting of the first two resonant speeds and the attenuation of the steady state vibration response of the rotor bearing system in the horizontal and vertical directions at the resonance frequencies. When the MRE layer is subjected to a magnetic field generated by an electric current produced in the magnetic coil, the horizontal and vertical vibration responses are increased at the resonant speeds but decreased at other rotational speed ranges. Furthermore, the first two resonant speeds in the horizontal and vertical directions decrease further with the increase of the electric current.

Stability analysis of multi-trigger nano tube sandwich structures considering thermal and magnetic effects

This research investigates the stability analysis of multi-trigger nanotube-based sandwich structures that carry fluid subjected to external stimulus. Acrylic-based material and magnetorheological elastomers (MRE) are considered multi-trigger cores in which the external stimulus alters the mechanical properties of the core and, subsequently, the sandwich structures. The system is subjected to an external magnetic field while the ambient temperature varies. The results demonstrate that incorporating a multi-trigger viscoelastic core can accelerate the divergence instability of the non-conservative system while delaying its flutter. Additionally, the impact of the external magnetic field, as a control parameter, for the frequency and stability region of the MRE is more significant than that of the Acrylic-based material. Furthermore, employing Acrylic-based material with a higher shear modulus in a constant magnetic field leads to a more stable system. Moreover, the effect of the external magnetic force on stability is affected smoothly by the ambient temperature. Finally, the influence of temperature on stability is nearly the same for both MRE and Acrylic-based material, with a more pronounced effect observed in systems with larger length-to-diameter ratios.

Properties and influence of magnetic fields on iron particles of anisotropic magnetorheological elastomers

The magnetorheological elastomer (MRE) is an intelligent material whose mechanical properties can be rapidly adjusted under a magnetic flux density. This material’s mechanical properties change due to the interaction between the iron particles inside the material. Understanding the influence of magnetic flux on iron particles in MRE materials is essential. Studies have proven that the distance and angle of inclination between iron particles significantly affect the magnetic flux density and the interaction force between the particles. Therefore, the distribution of iron particles substantially affects the material’s properties. However, understanding magnetic flux through magnetic particles is necessary to improve the material’s mechanical properties and to design magnetic field systems in systems using the materials. This study maps three problems affecting magnetic flux density to the properties of MRE. First, the mechanical characteristics of the MRE were presented in the frequency, amplitude, magnetic flux density, and magnetic flux inclination domains relative to the particle chain. Next, the influence of the magnetic flux on the particle chain was investigated based on the dipole interaction model and the magnetic force on iron particles. The finite element method also explored the magnetic flux distribution in the MRE material. Finally, the response of the single-degree-of-freedom damping system is tested experimentally. The results show that the influence of the magnetic flux on the iron particles in the MRE material is significant. The research results aim to improve the mechanical properties of MRE materials.

Development of a Novel Magneto-Rheological Elastomer-Based Semi-Active Seat Suspension System

Human operators in the transportation sector are exposed to whole-body vibration (WBV) while driving. Occupational exposure to WBV, predominant at low frequencies (<20 Hz), has been linked to spinal injuries and reduced functioning. This study aims at the design development of a novel semi-active seat suspension system featuring magneto-rheological elastomers (MREs) to mitigate the WBV. The proposed suspension system allows a greater range of strokes, while ensuring the MRE remains within an acceptable level of deformation. Several MRE samples were fabricated and characterized under shear mode. Afterward, a field- and frequency-dependent phenomenological model was developed to predict the viscoelastic properties of MREs as functions of both the excitation frequency and applied magnetic field. The MRE material model was subsequently used to design and optimize an adaptive seat suspension system incorporating a C-shaped MRE-based isolator in parallel and series with passive springs. The proposed adaptive seat suspension system demonstrated a frequency shift of 29% by increasing the applied current from 0 to 2 A. Finally, a 6-DOF lumped parameter model of a seated human subject combined with the proposed semi-active suspension system featuring the MRE isolator has been formulated to investigate the vibration transmissibility from the floor to the subject’s head.

Experimental study on vibration suppression for robotic milling using an MRE absorber

During the robotic milling process, vibration is one of the main factors that affect the machining accuracy and surface quality due to the low stiffness of the robot structure. Intelligent material, magneto-rheological elastomer (MRE), owns the features of adjustable stiffness, reversible and fast response, has been gradually used for vibration suppression. Therefore, to suppress the forced vibration for robotic milling, this paper used the principle of vibration absorption and combined it with MRE material to design a snubber. A series of excitation and milling experiments were carried out to evaluate its vibration attenuation characteristics. In the excitation experiment, sine signals with frequencies of 40 Hz, 42.02 Hz and 60 Hz with the same amplitude of 5 N were applied to the MRE absorber. In the milling experiment, the dominant frequencies under speeds of 800 RPM, 840 RPM and 1200 RPM were analyzed first. Then, the vibration mitigation characteristics of the MRE absorber during robotic milling of aluminum alloy were explored by adjusting the current. Experimental results showed that under the action of MRE absorber, the acceleration responses are suppressed effectively. In detail, after tuning the current, the amplitude and the root mean square of vibration acceleration in three directions of sinusoidal excitation could be suppressed by more than 19.23% and 7.35% correspondingly. The power spectral density value of the peak frequency could be reduced by more than 69.13%. In milling experiments, the MRE absorber also achieved certain vibration absorption effects. Furthermore, the surface roughness of the workpiece was also fallen by more than 16.51% which provides support for further engineering application in the field of robotic milling. Undoubtedly, the absorber needs further optimization to achieve better vibration suppression ability and a larger working bandwidth.

Theoretical and experimental research on the mechanical properties of magnetorheological elastomers based on PDMS

Magnetorheological Elastomers (MREs) are smart materials with the ability to modulate their mechanical properties by changing the external magnetic fields, offering extensive potential for applications requiring variable stiffness and damping devices. A comprehensive mechanical model that explains the influence of loading conditions on the performance of MRE is crucial for understanding their intrinsic mechanisms during operation, and for the design, analysis, and improvement of intelligent energy dissipation and vibration control devices based on MRE. In this study, a four-parameter mechanical model was established to reveal the intrinsic mechanisms about the effects of external magnetic fields, loading frequency, and strain amplitude on the storage modulus, loss modulus, equivalent stiffness, and equivalent damping of MRE materials. The dynamic mechanical properties of the MRE materials prepared from carbonyl iron powder and PDMS were tested, and parameter identification of the established model was performed. The comparison results between the theoretical model analysis and the testing results demonstrated that the proposed mechanical model effectively characterizes and predicts the mechanical behavior of MRE materials. Furthermore, based on the prepared MRE materials, a stiffness-controllable energy dissipator operating in shear mode was designed and fabricated, and the mechanical performance of the shear energy dissipator was experimentally evaluated. This research provides a basis and guidance for the design and mechanical performance analysis of devices based on MRE, confirming the feasibility of MRE materials as core components in intelligent energy dissipation devices.

Dynamic Compression Simulation of Magnetorheological Elastomer Using Bouc-Wen Hysteretic Model

This paper explores the versatility of Bouc-Wen hysteresis model in simulating the dynamic behaviour of magnetorheological elastomer (MRE) material. Bouc-Wen model have been used in many field of science including modelling the hysteresis phenomenon happen in magnetic material, elastomer, base isolation of structures and many more. Introduced by the Robert Bouc, this nonlinear hysteretic model has been modified by many researchers to suit different applications. Compression testing of MRE material under high strain amplitude produces nonlinear hysteresis curve based on stress-strain data. Bouc-Wen hysteretic model has been found to be able to simulate the hysteresis curve of MRE material using parameter identification method within MATLAB Simulink.

Development of magnetorheological elastomer railway pads with a tunable stiffness/damping property for railway fastening systems

The railway pad plays an irreplaceable role in isolating the vibration and noise from rail/wheel interaction in railway components. A railway pad with variable stiffness and damping properties can adapt to various railway operating conditions for suppressing of railway noise and vibration. Unfortunately, to meet the practical requirements in railway fastening systems, which the railway pad should be able to bear heavy loads with low stiffness, both the material development and structural design need to be addressed for the application of magnetorheological elastomer (MRE). In this work, an MRE railway pad is designed, developed and experimentally tested. As illustrated by experimental results, the obtained MRE materials illustrate an obvious magnetorheological effect with the highest efficiency of 171% on storage modulus and 70% on loss factor. Coupling with the magnet controlling unit, the MRE railway pad is capable to control the stiffness and damping property under high loads. By adjusting the coil’s current from 0 A to 5 A, its static stiffness exhibits an enhancement from 37.9 kN/mm to 68.4 kN/mm, and the damping property increases from 8776.3 N•s/m to 10866.3 N•s/m. These results in this study are not only a successful demonstration of delivering a tunable stiffness and damping capability of the railway pad, but also pave the way for the development of MRE materials to achieve more rational applications.

A new vibration isolator integrating tunable stiffness-damping and active driving properties based on radial-chains magnetorheological elastomer

In this study, a new vibration isolator integrating tunable stiffness-damping and active driving properties based on Magnetorheological Elastomer (MRE) embedding radial iron chains is proposed. Displacement/base excitations and periodic fluctuation current tests have been utilized to illustrate the fundamental dynamic properties and function of the proposed MRE vibration isolator. The force–displacement/velocity characteristics under different amplitudes/frequencies/currents input show the significant tunable range of the stiffness and damping and hysteresis loop area under the displacement excitation test, which is also described by the established Hyperbolic hysteresis model. Under the base excitation test with the sweep sinusoidal acceleration signals, it has been shown that the transmission properties can be adjusted by the applied current, and has a significant dependency on the amplitude of the acceleration excitation due to the Payne effect. Finally, it has been illustrated that the MRE component can drive a mass of 78 times self-weight in a 10 Hz excitation frequency under the periodic fluctuation current input. Therefore, the adjustable stiffness-damping and active driving force properties of the MRE material itself make the proposed MRE vibration isolator show great application potential in the passive, semi-active and active vibration control area with the fail-safe property.

Dynamic characterization of the magnetomechanical properties of off axis anisotropic magnetorheological elastomer

Abstract The use of magnetorheological elastomers in the mechanical and acoustic fields, by the automotive, aeronautical, and building industries, is currently developing strongly and rapidly. The perfect understanding of the capacity of smart insulation based on the absorption of the vibratory waves by magnetorheological elastomers materials passes by the knowledge of their dynamic mechanical behavior. In this present work, we have characterized the dynamic mechanical properties of the magnetorheological elastomer off axes anisotropy by the inclination, of different angles (15°, 30°, and 45°), of the pseudo-fibers of the iron particles formed by the application of a magnetic field at different intensities using an optimal loading rate of 30%. The rubber specimens were prepared by mixing micron-sized iron particles dispersed in room temperature vulcanized (RTV) silicone rubber by solution mixing. The experimental results obtained show a clear dependence of the effect of inclusion of ferromagnetic chains on the magnetomechanical properties. It is observed that the mechanical properties are better when applying a magnetic field of 0.6 T with an angle of inclination of 45°. The improvements added in this work could be useful in several industrial applications, such as automotive, aeronautic through adaptive control of damping and vibration level.

Vibration control of jacket offshore platform through magnetorheological elastomer (MRE) based isolation system

Undesirable vibrations in offshore platforms due to ocean loadings may reduce platform productivity and increase the fatigue failure. This study proposes a magnetorheological elastomer (MRE) based isolation system to control the jacket platform oscillations and its effectiveness is numerically evaluated. The working principle and design method of MRE-based isolation system are proposed, and MRE materials with high magnetorheological effects are conceptually designed. Practical jacket offshore platforms are selected for case studies. Semi-active fuzzy controller (SFC) is utilized to achieve real-time non-resonance vibration control. The proposed fuzzy core is constructed conceptually by the dynamic analysis of object structure. Numerical results demonstrate that MRE isolation system with SFC significantly reduces the maximum, minimum and RMS of the deck displacement and acceleration under realistic irregular waves at different sea states. MRE system could also reduce the response spectrum peaks and present robustness under various deck's mass. The present study proves the feasibility of MRE isolation systems in the application of vibration control for marine structures.

Magnetorheological Elastomers–Material Properties and Actuation Capabilities

Magnetorheological elastomers (MRE) are composite materials, which consist of a soft elastomer matrix filled with soft-magnetic particles. Mechanical and magnetic properties of silicone-based MRE with iron particles in different concentrations as well as their alteration in a magnetic field with variable strength are described in this paper. By applying a magnetic field already during the preparation of MRE bodies, magnetic elastomer materials with anisotropic properties are generated. The mechanical, magnetic and electric properties of such anisotropic MRE materials were studied as well. Beside the exploitation of MRE for applications of vibration reduction, these materials can also be utilized for actuation purposes. The working principles of linear and radial MRE actuators are described. Moreover, some possible applications of linear MRE actuators for haptic feedback and precisely controllable pumps as well as the possible use of radial MRE actuators for proportional valves and for locking devices are outlined in the paper as well.

Experiments and Numerical Implementation of a Boundary Value Problem Involving a Magnetorheological Elastomer Layer Subjected to a Nonuniform Magnetic Field

Abstract This study investigates experimentally and numerically the response of a magnetorheological elastomer (MRE) layer placed atop an electromagnetic coil. The MRE layer is deflected upon application of a current in the coil, which creates highly nonuniform magnetic fields. Isotropic and transversely isotropic layers (i.e., containing chains of magnetic particles) are tested experimentally, and the isotropic layer exhibits the largest deflection. To enhance the energetic efficiency of the model device, an iron core is introduced inside the electromagnetic coil, thereby leading to an increase in the resulting magnetic field near the center of the MRE layer. In parallel, the boundary value problem —including the MRE layer, the coil, the core (if present) and the surrounding air—is modeled numerically. For this, a magneto-mechanical, vector potential-based variational formulation is implemented in a standard three-dimensional finite element model at finite strains. For the material description, a recently proposed analytical homogenization-guided model is used to analyze the MRE in the “coil-only” configuration. It is then employed to predict the response of the layer in the “coil plus core” configuration, thus circumventing the need for a separate material characterization procedure. The proposed numerical simulation strategy provides a deeper understanding of the underlying complexity of the magnetic fields and of their interaction with the MRE layer. This study also reveals the importance of modeling the entire setup for predicting the response of MRE materials and, as a result, constitutes a step toward designing more efficient MRE-based devices.

Magnetorheological elastomers — An underestimated class of soft actuator materials

In this paper, the results of various investigations on the viscoelastic and magnetic properties of magnetorheological elastomers (MRE) in magnetic fields of variable strength, are reported. These characteristics have a strong influence on the behavior of MRE in various applications such as vibration damping and tunable vibration absorbers. Moreover, the actuation capabilities of MRE with different kinds of deformation in a magnetic field are considered. The degree of deformation depends on the magnetic field strength and its gradient and can reach about 10%. When removing the magnetic field, the MRE body relaxes back to its initial shape. MRE materials can be used for linear actuators, where the MRE body is deformed due to the attraction by a magnetic circuit acting from one side. Such linear actuators may be applied for haptic feedback and pumps. However, ring-shaped MRE bodies can also deform radially around their cylindrical axis, if the magnetic field is oriented correspondingly. This unusual type of deformation allows the realization of a proportional valve, whose opening is controlled by the magnetic field strength. Similar configurations can be used for controllable seals, for locking devices and even for inchworm drives. Various versions of this actuation principle are discussed in the paper.

A study of the effect of mechanical preloads on hysteresis loop of magnetorheological elastomers

In this work, an investigation of the effect of mechanical preloads on the hysteresis loop of composite soft magnetorheological elastomer (MRE) was carried out. MRE is a “smart” composite material that consists of magnetically permeable particles in a non-magnetic polymeric elastomer. When subjected to an external magnetic field, a large deformational change occurs in the mechanical properties of these materials. Due to their coupled magnetomechanical response, these materials have been found suitable for various engineering applications. Inspired by experimental work, we present a model of the effect of mechanical preloads on the magnetization response of MRE based on a general continuum formulation. Using the Jiles - Atherton (JA) model parameters derived from the fitting of experimental measurement, the hysteresis loop of isotropic MRE was numerically resolved, which was then coupled to mechanical fields based on an energetically constitutive model valid for finitely strained MREs. Simulation analysis is performed for uniaxial stresses parallel to the direction of the applied magnetic field. For the applied tensile and compressive stresses, only a small change is observed in the hysteresis loop of these materials. Additionally, microscale modeling of the magnetization behavior of the isotropic MRE based on experimental results was performed. Considering the interaction between the magnetic particles, the magnetic and mechanical fields are resolved explicitly inside the composite material. A computational homogenization scheme was utilized to relate the microscopic behavior to the effective macroscopic properties of the MRE. In principle, the predicted effective magnetization behavior is observed to agree with the measured hysteresis loop of MRE materials.

Novel high efficiency deterministic polishing method using magnetorheological elastomer

Magnetorheological elastomer (MRE) is a kind of intelligent material with excellent magnetic-induced rheological features. It has been widely applied in fields like vibration control, soft robots, smart sensing, electromagnetic shielding, etc. In theory, MREs have flexible and controllable rheological properties, which make it possible to become a high efficient deterministic polishing medium as that of magnetorheological fluids. In this paper, a novel polishing method using MRE material as the deterministic polishing tool is proposed. This method utilizes the magnetorheological effect of MRE to generate stronger instantaneous shear force which has advantages over that of traditional magnetorheological fluid finishing. First, a new MRE material suitable for magnetorheological principle finishing is prepared, and the mechanical properties of MRE are characterized. In order to make sure that the polishing fluid can run into the polishing zone and improve the polished surface quality, special pattern and micro structures are well designed and engineered on the MRE surface. Compression and wear property are investigated to understand the nature of this novel tool. Then, a mathematic model considering the contribution weights of shear stress and normal pressure of MRE polishing is established and discussed. Finally, polishing experiments are carried out on an optical glass, and a stable removal function is obtained. Results demonstrate that this novel MRE polishing can achieve high efficiency and determinability in optical manufacturing, which proves the feasibility of the novel polishing method using MRE tool.

Dynamic stability analysis of a sandwich beam with magnetorheological elastomer core subjected to a follower force

In the present study, the effect of using magnetorheological elastomer materials and a magnetic field on the dynamic stability of a sandwich beam under a follower force has been investigated for various boundary conditions. The considered sandwich beam consists of a magnetorheological elastomer core constrained by elastic layers. The structural governing equations are derived using Hamilton’s principle and solved by the finite element method. The validity of the result is examined by comparison with those in the literature. The effects of variation in the parameters such as magnetic field intensity and the thickness of the layers on the stability of the sandwich beam are studied. Finally, some conclusions for the effects of the magnetic field intensity on the magnetorheological elastomer sandwich beam subjected to the follower force are discussed.

A mechanical characterization of electroconductive magnetorheological elastomer and semi-analytical modeling of magnetic force

Materials with novel properties and compounds of intelligent material combinations are a key to innovation in various successful sectors of the global industry as well as for its export. Magnetorheological elastomer materials have interesting physical properties; most of these properties are modified and adapted under the influence of external parameters such as the magnetic field. In this work, an experimental characterization of the magnetorheological elastomers (MRE) loaded with 20% of the iron particles was made. The results showed that the properties of these materials can be modified very selectively and reversibly under the influence of magnetic field, where the stiffness of the material varies depending on the magnetic field intensity that influences the attractive force between iron particles.