Mechanical Properties Of Magnetorheological Elastomers Research Articles

An Adaptive Elastic Support Seat-Based Magnetorheological Elastomer for Human Body Vibration Reduction.

This paper introduces an electromagnetic structure utilizing the controllable mechanical properties of magnetorheological elastomer (MRE) materials through magnetic flux. An adaptive elastic foundation composed of these materials is explored for vibration reduction and frequency modulation. This study investigates these effects using both a single-mass model and a coupled human-seat model. For objects supported by the adaptive elastic foundation, increasing the magnetic flux enhances the stiffness and damping, thereby significantly reducing the peak response while slightly increasing the resonance frequency. Strategies such as increasing the magnetic flux, reducing the object mass, and minimizing the system's degrees of freedom and internal damping contribute to enhancing the vibration reduction and frequency modulation in the adaptive elastic foundation. The simulation results indicate that for a seated human (weighing between 72.4 kg and 88.4 kg), the adaptive elastic foundation reduces the head peak response by approximately 15.7% and increases the resonance frequency by approximately 3.4% at a magnetic flux of 138 mT.

Experimental study and mechanism analysis on the effect of pre-curing time on the microstructure and mechanical properties of magnetorheological elastomers under compression

The effects of the pre-curing time before exposing the carbonyl iron particles (CIPs) filled liquid polydimethylsiloxane (PDMS) mixture to a preparatory magnetic field on the magnetorheological (MR) effects of the magnetorheological elastomers (MREs) were experimentally and theoretically investigated. The anisotropic MRE samples with different pre-curing time were firstly fabricated and their compressive MR effects were tested. The results showed that the longer pre-curing time induces the shorter and more irregular particle chains formed in the MREs, and the sample pre-cured for 20 min showed the maximum MR effect. Then based on the rheological characterization, a rheological model was proposed to predict the rheological property evolution of CIPs/PDMS mixture with respect to the pre-curing time, and a modified three-dimensional (3D) particle dynamics (PD) model was developed to simulate the particle structure evolution in the MRE mixtures under a preparatory magnetic field. The simulation results showed that short chains were first formed owing to the magnetic attraction between the adjacent particles. Then these short chains approached each other to form long chains and even thick chain-like clusters. The later process can be restrained by increasing the pre-curing time, thus more short and incompact particle chains are formed in the MREs. Lastly, simplified microstructure models representing the wavy chains were used to explore the effect of particle arrangement on the MR effect of the MREs under compression. It is found that the wavy chains with incompactly packed particles are beneficial for improving the MR effect owing to the strong transverse magnetic attraction between the neighboring particles. This work demonstrates that PD simulation is an efficiency method to predict the particle arrangement evolution in the MRE mixture, and the possibility to tailoring the microstructures of the MREs by adjusting the viscosity of MRE mixtures to improve their MR effects, while keeping a high zero-field modulus simultaneously.

A physics-guided deep learning model for predicting the magneto-induced mechanical properties of magnetorheological elastomer: Small experimental data-driven

Magnetorheological elastomer (MRE) is a novel intelligent material, which shows excellent potential in vibration control applications. Previous researches have fully demonstrated that the magneto-induced shear storage modulus of MRE largely determines the vibration control effect. However, both existing theoretical and experimental ways to measure the magneto-induced shear storage modulus of MRE face their own shortage. Therefore, a novel physics-guided deep learning model is proposed to efficient predict the magneto-induced mechanical properties of MRE based on Magnetic Dipole theory and data-driven methods. A small database is built by collecting the magneto-induced shear storage modulus of MRE with different material ratios tested on a special shear rheometer. The proposed model trained with small training samples and its prediction results fit well with experimental values (average R2 of 0.99) which is superior to existing constitutive models. The training only takes 25 s, which significantly shortens the time compared to the experiment. Furthermore, the proposed model effectively predicts the magneto-induced storage modulus of MRE and has good generalization and superior transfer performance.

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.

Microscopic double-chain sawtooth model and macroscopic four-parameter fractional-order derivative viscoelastic model based on magnetorheological elastomers

In order to restore the distribution of ferromagnetic particles in magneto-rheological elastomers to the greatest extent, the magnetotropic effect of magneto-rheological elastomers is more accurately represented, and the dynamic mechanical properties of magneto-rheological elastomers are more accurately reflected. In this paper, based on the dipole theory, a new microscopic model of magnetorheological elastomer, the double chain sawtooth model, is proposed based on the chain model and the main chain adsorption model, and a macroscopic viscoelastic mechanical model of magnetorheological elastomer, the four-parameter fractional order derivative improvement model, is proposed based on the classical macroscopic mechanical parametric model and the fractional order derivative model. A microscopic model of magnetorheological elastomer was combined with a macroscopic model to describe its mechanical properties. Isotropic and anisotropic magnetorheological elastomers with different mass fractions and different silicone oil contents were prepared using silicone rubber as the matrix and carbonyl iron powder as the filling phase, and dynamic shear tests were conducted to verify the validity of the model.

Magneto-mechanical properties of anisotropic magnetorheological elastomers with tilt angle of magnetic chain under compression mode

Characterization of mechanical properties of magnetorheological elastomers (MREs) is essential for the design of smart materials and devices with customized features and functionalities. While the properties of MREs under shear mode have been extensively researched, MREs with tilt angle under compression mode have been less exploited. In this study, a magneto-mechanical model of anisotropic MREs is established based on magnetic dipole theory and energy method considering the reconfiguration effect of compressive strain on the microstructure of the magnetic chain. This leads to the provision of a dynamic magneto-mechanical model of the anisotropic MREs, incorporating the magneto-induced mechanical model, by using the robust fitting method. Experiments were conducted to assess the force–deflection (stress–strain) characteristics of MREs with tilt angle under compression mode, subject to the regulation of the tilt angle of magnetic chain, magnetic flux density, and mass fraction of magnetic particles. The magnetic-induced modulus, obtained from the theoretical model, is experimentally verified through magneto-mechanical testing, alongside an analysis on the dynamic mechanical properties under different dynamic strain amplitudes and frequencies. The mean square error (MSE) in terms of magneto-mechanical storage modulus in the robust fitting ranges from 2.73% to 10.86%. Experimental results also show that the range of magneto-induced stress (typically from 178 KPa to 74.6 KPa) decrease when the tilt angle of the magnetic chain increases (from 15° to 25°) corresponding to 60% mass fraction. The compression strain of the anisotropic MREs, affecting both the spacing of adjacent magnetic particles and the tilt angle of magnetic chain, causes significant changes in the magnetic-induced modulus. In addition, the hysteresis loops under different deformation (Mullins effect) show an increasing energy dissipation with decreasing tilt angle.

Effect of Carbonyl Iron Particle Types on the Structure and Performance of Magnetorheological Elastomers: A Frequency and Strain Dependent Study.

Magnetorheological elastomers (MREs) are smart viscoelastic materials in which their physical properties can be altered when subjected to a varying magnetic field strength. MREs consist of an elastomeric matrix mixed with magnetic particles, typically carbonyl iron particles (CIPs). The magnetic field-responsive property of MREs have led to their wide exposure in research. The potential development and commercialization of MRE-based devices requires extensive investigation to identify the essential factors that can affect their properties. For this reason, this research aims to investigate the impact of CIPs’ type, concentration and coating on the rheological and mechanical properties of MREs. Isotropic MREs are fabricated with four different CIP compositions differing between hard or soft, and coated or uncoated samples. Each MRE composition have three different concentrations, which is 5%, 10%, and 20% by volume. The dynamic properties of the fabricated samples are tested by compression oscillations on a dynamic mechanical analyzer (DMA). Frequency and strain dependent measurements are performed to obtain the storage and loss modulus under different excitation frequencies and strain amplitudes. The emphasis is on the magnetorheological (MR) effect and the Payne effect which are an intrinsic characteristics of MREs. The effect of the CIPs’ type, coating, and concentration on the MR and Payne effect of MREs are elucidated. Overall, it is observed that, the storage and loss modulus exhibit a strong dependence on both the frequency excitations and the strain amplitudes. Samples with hard and coated CIPs tend to have a higher MR effect than other samples. A decrease in the storage modulus and non-monotonous behavior of the loss modulus with increasing strain amplitude are observed, indicating the Payne effect. The results of this study can aid in the characterization of MREs and the proper selection of CIPs grades based on the application.

Multiscale numerical modeling of magneto-hyperelasticity of magnetorheological elastomeric composites

Mechanical properties of magnetorheological elastomers (MREs) are essential for their engineering applications. While the magneto-elastic responses of MREs under large deformation are obtained with experimental methods, microstructure-based modeling and simulation can indicate the physical mechanisms that further provide guidelines for engineering design. We herein propose a computational micromechanics-based multiphysics coupling model to reveal the overall magneto-hyperelastic properties of MREs. Interactions among ferromagnetic particles in MREs are defined in terms of magnetic body forces. The coupled magnetic and mechanical fields are solved in the three-dimensional representative volume elements with chained microstructures under large deformation. The macroscopic stresses are obtained by the computational homogenization procedures with consideration of the microscopically coupled fields of stresses and magnetic body forces. Effects of demagnetizing field and microstructures on the overall magnetic stresses are particularly emphasized. The mechanical properties obtained from several groups of experiments are quantitatively predicted and interpreted which further verifies the applicability and correctness of the proposed method.

Study on the dynamic mechanical properties of magnetorheological elastomer (MRE) with Fe@C

Magnetorheological elastomer (MRE) is a promising type of smart material, suitable for shock absorbers in tank engine mount systems. In order to improve the performance of the shock absorber, we improve the magnetorheological (MR) effect of the MREs and reduce its loss factor by enhancing the interaction force between the particles and the substrate. In this work, a novel carbon-coated iron material was prepared by heat treatment, and then carbon-coated iron (Fe@C) of different proportions was added to natural rubber to prepare MRE samples. The tensile strength and elongation at break of the MRE samples were tested by a universal electronic tension machine. The results indicated that better bonding strength between the particles and the matrix increased in tensile strength. The MR effect and the loss factor of the MRE samples were tested by a rheometer. The results demonstrated that the MR effect of MREs modified with Fe@C was significantly improved, and the loss factor of this kind of MRE decreased markedly.

The study on the mechanical properties of magnetorheological elastomers under triaxial compression

In order to design magnetorheological elastomers (MREs) based craftsmanship for metal forming, a comprehensive study on the mechanical properties of MREs under triaxial compression is required. An experimental setup integrating free compression and triaxial compression is designed to characterize isotropic MREs specimens under compression mode. The results showed that the MREs specimen in mold had successively experienced free compression stage, transition stage and triaxial compression stage during the experiment. The stress-strain curves of the MREs specimen changed when the concentration of magnetic particles increased from 0 to 44.7%, and the strain required to reach the transition stage was reduced. The effect of magnetic flux density on the stress-strain curves of the MREs specimen depended on the concentration of magnetic particles. The measured data obtained at different strain rates revealed maximum changes of 15.7% and 0.096% in volume compression modulus and Poisson ratio, respectively, which occurred under the magnetic flux density of 200 mT and CIP concentrations of [Formula: see text]. In this study, through a set of experiments, the stress-strain curves of the MREs specimen under different concentrations was elucidated, and their effects on the volume compression modulus and Poisson ratio were discussed.

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.

Effect of abrasive particles on mechanical properties of magnetorheological elastomer

This work reported a novel magnetorheological elastomer (MRE) with different concentrations and sizes of abrasive grains, and its mechanical properties were investigated with or without magnetic field. Firstly, the MRE polishing wheel was prepared by molding with magnetic field, the microstructures of these MRE polishing wheels were observed, the magnetostrictive distribution of abrasive grains and ferromagnetic grains were discussed, and the magnetic properties was tested. Then, the magnetic hardness testing, magnetic compression experiments, and friction performance testing were conducted to investigate its mechanical properties and friction properties. Finally, a polishing experiment was designed to study the polishing performance of MRE polishing wheels. The results showed that the magnetic hardness, Young's modulus, and friction reduction of MRE polishing wheels were increased by adding abrasive grains, and the surface quality of workpiece after polishing was improved.

Characterization of a magneto-active membrane actuator comprising hard magnetic particles with varying crosslinking degrees

We developed membrane actuators from magnetorheological elastomers (MREs) with hard magnetic particles using a novel mold-free fabrication procedure. The fabrication method improved the manufacturing efficiency via doctor blading and the two-stage curing process. To evaluate the performances of the membrane actuators, we monitored changes in the properties of the MREs in terms of the crosslinking degree in their polymeric matrices. The microstructure, curing behavior, magnetic properties, and mechanical properties of MREs were measured using a scanning electron microscope, vibrating sample magnetometer, rheometer, uniaxial tensile testing system. Deflection of the membrane actuators was measured using a custom-designed deflection system. The saturation magnetization (Ms) and remanence (Br) of MREs decreased as the crosslinking degree of matrices increased. Their elastic moduli (E) also decreased as the crosslinking degree increased. Meanwhile, in case of integrated analysis, an anisotropic sample with an initial curing time of five minutes exhibited the largest actual deflection, although the particles were aligned with the magnetic fields after crosslinking of 6.01% was achieved. By identifying the relationship between the properties of MREs and the crosslinking degree in its polymeric matrix, the MREs used to fabricate membrane actuators can be tailored for specific applications: pumps, valves, microlenses, and cell stimulators.

The dynamic mechanical properties of magnetorheological elastomer: Catalytic effect of carbonyl iron powder

The vulcanization time of the natural rubber–based magnetorheological elastomers and natural rubber was tested by the rotor-less vulcanizer. Result shows that the magnetorheological properties were best after adding 190 copies of carbonyl iron powder. From the test of rotor-less vulcanizer and equilibrium swelling method, it could be found that, after adding 190 copies of carbonyl iron powder, the crosslink density was increased by 11% and the vulcanization time was shortened by 20%. The catalytic activity of accelerator mainly originated from its ability of forming active vulcanizing agent with sulfur atom, and the possible mechanisms had been given. The carbonyl iron powder in magnetorheological elastomers improved the magnetorheological properties and the efficiency of vulcanization.

The study of mechanical properties of magnetorheological elastomers under compressive stress

The study of magnetorheological elastomers is one of the major areas of searching for construction materials with unique properties. These are smart composite materials which constantly find new areas of use because they combine the advantages of elastomers and ferromagnetic materials. This article presents the results of study of the mechanical properties of magnetorheological elastomers under compressive stress. As part of the study, a series of compression cycles was performed at different magnetic induction values, strain amplitude and input frequency. The influence of each parameter on the material characteristics was determined utilizing a rheological model of a viscoelastic material. The presented results were supplemented with methodology of measurement and sample preparation as well as information related to the construction of the testing station.

Modeling selected mechanical properties of magnetorheological elastomers

Magnetorheological elastomers are an important group of non-classical engineering materials. The aim of the works carried out is to study the influence of magnetic field on a series of mechanical properties of composite materials in this group. Based on prior analyses, a limited usability of the viscoelastic material model was identified for the purpose of describing the stress-strain relationship in magnetorheological elastomers. Therefore, it has become necessary to propose changes to this rheological model. The present article includes theoretical considerations in relation to the mathematical derivation of functions allowing to account for the influence of strain amplitude on the progressive character of the mechanical hysteresis loops in the materials under discussion. It also provides a detailed analysis of the derived formulas together with a discussion, supplemented with the description of employed simplifying assumptions.

The study of enhancement of magnetorheological effect based on natural rubber/thermoplastic elastomer SEBS hybrid matrix

Magnetorheological elastomers are one kind of smart materials which consist of matrix materials and magnetic particles. The mechanical properties of magnetorheological elastomers were controllable under an external magnetic field. Applications of magnetorheological elastomers are limited as a result of their poor magnetorheological effect and mechanical performance, so enhancing the magnetorheological effect of them is critical for their application. Styrene-ethylene-butylene-styrene based thermoplastic elastomer was added to natural rubber to fabricate hybrid matrix–based magnetorheological elastomers. Zero modulus of magnetorheological elastomers increased from 0.50 to 0.64 MPa and magnetorheological effect increased from 28.00% to 43.75% with the addition of styrene-ethylene-butylene-styrene based thermoplastic elastomer. The contact angle of carbonyl iron particles with the matrix showed that styrene-ethylene-butylene-styrene based thermoplastic elastomer can improve the compatibility of carbonyl iron particles with the matrix. Fourier-transform infrared spectroscopy analysis has been carried out to investigate the internal structure of hybrid matrix–based magnetorheological elastomers.

Effect of Electromagnetic Force on Dynamic Mechanical Properties of the Magnetorheological Elastomer Under Compression Mode

Abstract Under the compression mode, the direction of force on the magnetorheological elastomer (MRE) is parallel to the direction of electromagnetic force, so the effect of electromagnetic force on its dynamic mechanical properties cannot be ignored. Therefore, this paper focuses on the effect of electromagnetic force on the dynamic mechanical properties of MRE under compression mode. A new type of testing device was designed and processed. Under a different loading frequency, strain amplitude and external magnetic field, dynamic mechanical properties of MRE were tested, respectively. The result shows that the stiffness and energy dissipation capacity of MRE increase with the current and loading frequency. The stiffness of MRE decreases with the increase in the strain amplitude, but the energy dissipation capacity increases. Comparing the force-displacement curve of MRE with or without the effect of the electromagnetic force, it shows that the electromagnetic force has a great effect on the stiffness of MRE and little effect on its energy dissipation capacity. When the electromagnetic force is removed, the stiffness of MRE decreases, and the change rate of stiffness increases with current. The maximum change rate of stiffness is 5.65%.

A novel approach for fabricating adjustable zero field-modulus magnetorheological elastomer based on IPN matrix

Toughening modification of magnetorheological elastomer (MRE) is crucial necessity for developing intelligent MRE based devices. To prepare high performance MRE, the thermoplastic elastomer styrene-ethylene butylene-styrene triblock copolymer (SEBS) was added into polybutadiene rubber (BR) to prepare BR/SEBS interpenetrating network (IPN) matrix based MRE. The anisotropic samples were prepared by different vulcanization method under a magnetic field. The mechanical properties of MRE was measured by rheometer. The experimental results showed that the zero-field modulus of MRE was increased with the addition of SEBS. The measurement result of dynamic thermomechanical analysis (DMA) showed that the two-phase heterogeneous system was formed in matrix. The zero-field modulus of this MRE can be adjusted by the content of SEBS and vulcanization time and temperature since the SEBS does not participate in the vulcanization reactions and possess fluidity at high temperature. The MRE with adjustable zero-field modulus have promising advantages in the application of adaptive tuned vibration absorbers.

Magnetorheological elastomers with particle chain orientation: modelling and experiments

This work describes a new model of the magneto-induced shear storage modulus to simulate the shear behavior of magnetorheological elastomers (MRE) with particle chain orientation. The directionality of the chains is here described by using as a parameter the tilt angle with the external magnetic field. The magnetized particles within the MRE are described as magnetic dipoles. The model takes into consideration the dipole–dipole interaction and the magnetic field coupling between the particles in the chain. Magneto-rheological samples with different particle sizes and initial inclination angles have also been prepared and subjected to shear tests in a rheometer facility. The simulations from the model show that the magneto-induced modulus strongly depends on the initial inclination angle of the particle chain. The experimental data are also consistent with the results provided by the model, and confirm that the change of the initial tilt angle of the particle chain is an effective tool to improve the mechanical properties of magneto-rheological elastomers.