Investigation on Magnetorheological Effect of Novel Self-healing Magnetorheological Elastomers

Magnetorheological elastomers(MREs)hold significant promise in various fields such as automotive engineering,and civil engineering,where they serve as intelligent materials.Depending on the application of an external magnetic field,these materials exhibit varying magnetorheological and viscoelastic properties,including shear stress,yield stress,dynamic moduli,and damping.In this work,a new type of MRE,termed self-healing MREs(SH-MREs),has been developed by adding a novel self-healing agent into existing MREs.The dynamic modulus and loss factor of SH-MREs with different compositions have been characterized under various conditions of frequency,temperature,and strain.The results show that as the strain value increases,the loss factor also increases.Moreover,the loss factor initially increases and then decreases with increasing magnetic field strength.Although higher concentrations of ferromagnetic particles increase the loss factor,they enhance the operational range due to their better responsiveness to magnetic fields.SH-MREs demonstrate improved damping capabilities,attributed to the formation of coordination bonds between ferromagnetic particles and the self-healing agent.The stable structure increases the viscosity of MREs.The results of the regression model suggest a direct proportionality between sensitivity to the magnetic field and the ferromagnetic particle concentration.

Numerical Analysis on Magnetic-induced Shear Modulus of Magnetorheological Elastomers Based on Multi-chain Model

Based on the magnetic interaction energy, using derivative of the magnetic energy density, a model is proposed to compute the magnetic-induced shear modulus of magnetorheological elastomers. Taking into account the influences of particles in the same chain and the particles in all adjacent chains, the traditional magnetic dipole model of the magnetorheological elastomers is modified. The influence of the ratio of the distance etween adjacent chains to the distance between adjacent particles in a chain on the magnetic induced shear odulus is quantitatively studied. When the ratio is large, the multi-chain model is compatible with the single chain model, but when the ratio is small, the difference of the two models is significant and can not be neglected. Making certain the size of the columns and the distance between adjacent columns, after constructing the computational model of BCT structures, the mechanical property of the magnetorheological elastomers composed of columnar structures is analyzed. Results show that, conventional point dipole model has overrated the magnetic-induced shear modulus of the magnetorheological elastomers. From the point of increasing the magnetic-induced shear modulus, when the particle volume fraction is small, the chain-like structure exhibits better result than the columnar structure, but when the particle volume fraction is large,the columnar structure will be better.

Effect of Cyclic Deformation on Magnetorheological Elastomers

Fatigue properties of magnetorheological elastomer （MRE） samples were investigated based on cis-polybutadiene rubber by using a fatigue test machine. Three MRE samples with iron particles mass fraction of 60%, 70%, and 80% were fabricated, and their properties dependence of three strain amplitudes （50%, 75%, and 100%） were measured. The absolute magnetorheological （MR） effect, storage modulus, and loss modulus of MRE samples after fatigue were evaluated by a modified dynamic mechanical analyzer. The results revealed that MR effect, storage modulus, and loss modulus of MREs containing 80% iron particles depended strongly on the strain amplitudes and the number of cycles, while storage mod-ulus and loss modulus of MREs containing 70% iron particles also depended on the strain amplitudes and the number of cycles but not as strongly as sample which contains 80% iron particles, but the properties of MREs containing 60% iron particles after cyclic deforma-tion were almost independent of the fatigued conditions. In order to investigate the fatigue mechanism of MREs, the sample was carried out with a quasi-static tensile testing and its surface morphology during testing was observed in situ by scanning electron microscopy.

Experimental investigation on vibration characteristics of sandwich beams with magnetorheological elastomers cores

A sandwich beam specimen was fabricated by treating with MR elastomers between two thin aluminum face-plates.Experiment was carried out to investigate the vibration responses of the sandwich beam with respect to the intensity of the magnetic field and excitation frequencies.The results show that the sandwich beams with MR elastomers cores have the capabilities of shifting natural frequencies and the vibration amplitudes decrease with the variation of the intensity of external magnetic field.

Damping of magnetorheological elastomers

The damping property of magnetorheological elastomers(MREs) is characterized by a modified dynamic mechanical-magnetic coupled analyzer.The influence of external magnetic flux density,damping of matrix,content of iron particles,dynamic strain and driving frequency on the MREs' damping was investigated experimentally.The results indicate that the MREs' damping property depends on the interfacial slip between the inner particles and the matrix.Different from the general composite materials,the interfacial slip in MRE is affected by the external applied magnetic field.

Radiation Vulcanization of Magnetorheological Elastomers Based on Silicone Rubber

The fabrication of magnetorheological （MR） elastomers was studied by two vulcanization methods, including heat vulcanization （HV） and radiation vulcanization （RV）, were employed to fabricate MRE samples. The dynamical mechanical properties were characterized by using a dynamic mechanic analyzer. In particular, both the MR effect and its durability were investigated. The experimental results showed that RV samples have large magnetoinduced modulus, large zero-field modulus, and good durability property of MR effect. To explain these results, cubic deformation and plasticizer migration were analyzed. Large magneto-induced modulus of RV sample results from cubic deformation during vulcanization process. And the plasticizer migration results in better durability of MR effect.

Magnetic field-dependent inductance properties based on magnetorheological elastomer

Magnetorheological(MR)materials are a class of smart material,whose the mechanical/rheological state can be controlled under a magnetic field.Magnetorheological materials are typically fluids,gels,or elastomers.In this study,anisotropic and isotropic magneto-rheological elastomer(MRE)samples were fabricated using a silicone rubber matrix with carbonyl iron particles as filler particles.The magnetic field-dependent inductance properties of these samples were studied using inductors specially designed for the analysis.The effect of the filler particle content,fabrication conditions,and inductance properties were characterized using a self-built system in both constant and transient magnetic fields.These factors show a significant effect on the inductance properties of the MRE inductor under an applied magnetic field.The anisotropic MRE inductor was more sensitive than the inductor based on an isotropic MRE.Owing to the presence of a constant magnetic field,the inductance value of the MRE inductor decreased with an increase in the external magnetic field.An attempt in elucidation of the mechanism is reported here.This study may enable the MRE to be widely used in practical applications such as monitoring magnetic field or detecting the filler particle content inside MR materials.

Damping of Magnetorheological Elastomers

The damping property of magnetorheological （MR） elastomers is characterized by a modified dynamic mechanical-magnetic coupled analyzer. The influences of the external magnetic flux density, damping of the matrix, content of iron particles, dynamic strain, and driving frequency on the damping properties of MR elastomers were investigated experimentally. The experimental results indicate that the damping properties of MR elastomers greatly depend on the interfacial slipping between the inner particles and the matrix. Different from general composite materials, the interracial slipping in MR elastomers is affected by the external applied magnetic field.

Enhancement in Magnetorheological Effect of Magnetorheological Elastomers by Surface Modification of Iron Particles

In order to obtain magnetorheological （MR） elastomers with high magnetorheological effect, a family of anisotropic rubber-based MR elastomers was developed using a new form of chemical modification. Three different kinds of surfactants, i.e. anionic, nonionic and compound surfactants, were employed separately to modify iron particles. The MR effect was evaluated by measuring the dynamic shear modulus of MR elastomer with a magneto-combined dynamic mechanical analyzer. Results show that the relative MR effect can be up to 188% when the iron particles are modified with 15% Span 80. Besides the surface activity of Span 80, however, such high modifying effect is partly due to the plasticizing effect of Span 80. Compared with the single surfactant, the superior surface activity of compound surfactant makes the relative MR effect reach 77% at a low content of 0.4%. Scanning electron microscope observation shows that the modification of compound surfactant results in perfect compatibility between particles and rubber matrix and special self-assembled structure of particles. Such special structure has been proved beneficial to the improvement of the relative MR effect.

Analysis and Verification on the Chain-like Model with Normal Distribution of Magnetorheological Elastomer

Magnetorheological elastomer （MRE） is a new kind of smart materials, the rheological properties can be controlled rapidly by the external magnetic field. It is mainly composed of rubber and micron-sized ferromagnetic particles, which forms a chain-like structure. Therefore its mechanical, electric, and magnetic properties can be changed by the applied magnetic field, which is called as the magneto-induced effect. But this effect is not remarkable enough currently for the engineering application. So it is important for material preparation to optimize parameters to enhance the magneto-induced effect. In this work, based on chain-like model, some factors influencing the magneto-induced effect of MRE were analyzed theoretically by using dipole method with the normal distribution of chain＇s angle introduced. The factors included the oblique angle of particles chains, magnetic field intensity, and shear strain, etc. Some experiments were also carried out.

Dynamic damping property of magnetorheological elastomer

Magnetorheological elastomer(MRE) is a new kind of smart materials,its dynamic mechanic performances can be controlled by an applied magnetic field.MRE is usually used as a stiffness-changeable spring in the semi-active vibration absorber.In order to get perfect vibration control effect,low dynamic damping of MRE is need.But the dynamic damping of MRE was not studied deeply in the past.The dynamic damping of MRE was studied and analyzed.The influences of different test conditions including test strain amplitude,test frequency and test magnetic field were deeply studied.MRE sample and pure silicone rubber sample were prepared and tested under different conditions.The test results show that the main source of dynamic damping is the friction between iron particles and rubber matrix.And the friction is mainly influenced by the strain amplitude and test magnetic field.

Investigate the Effect of the Magnetic Field on the Mechanical Properties of Silicone Rubber-Based Anisotropic Magnetorheological Elastomer during Curing Process

In this investigation,a new silicone rubber-based MRE material was prepared to be used as a forming medium in manufacturing thin-walled complexshaped Ni-based tubes through the bulging process.Thus,it is significant to investigate the effect of magnetic field intensity,magnetic field loading time,and angle on the mechanical properties of the prepared MRE material during the curing process.The obtained results showed that increasing the magnetic field intensity during the curing process can improve the orientation of the chain structure in the elastomer matrix effectively.However,its mechanical properties are the best under the corresponding magnetic field intensity of 321 mT.Besides,by extending the magnetic field loading time in the curing process,the orientation of the chain structure was optimized,at the same time,the mechanical properties were also improved,and the best loading time is about 20–25 min.By changing the loading angle of the magnetic field during the curing process,the mechanical properties of the MRE were improved.When the loading angle of the magnetic field is 90°,the elastomer showed the best compression mechanical properties and excellent compression reversibility.Besides,for the anisotropic MRE material,the performance with magnetic compression is always better than that without magnetic compression.

Performance of magnetorheological elastomer based torsional vibration isolation system for dynamic loading conditions

Vibration isolation is an effective method to mitigate unwanted disturbances arising from dynamic loading conditions. With smart materials as suitable substitutes, the conventional passive isolators have attained attributes of semi-active as well as the active control system. In the present study, the non-homogenous field-dependent isolation capabilities of the magnetorheological elastomer are explored under torsional vibrations. Torsional natural frequency was measured using the serial arrangement of accelerometers. Novel methods are introduced to evaluate the torsional stiffness variations of the isolator for a semi-definite and a motor-coupled rotor system. For the semi-definite system, the isolation effect was studied using the frequency response functions from the modal analysis. The speed-dependent variations for motor-coupled rotor system were assessed using the shift in frequency amplitudes from torque transducers. Finite element method magnetics was used to study the variations in the non-homogenous magnetic field across the elastomer. The response functions for the semi-definite rotor system reveal a shift in the frequency in the effect of the magnetic field. Speed-dependent variations in the frequency domain indicate an increment of 9% in the resonant frequency of the system.

A novel approach to investigate effect of magnetic field on dynamic properties of natural rubber based isotropic thick magnetorheological elastomers in shear mode

The preparation of natural rubber based isotropic thick magnetorheological elastomers(MRE) was focused on by varying the percentage volume concentration of carbonyl iron powder and developing a test set up to test the dynamic properties. Effect of magnetic field on the damping ratio was studied on the amplification region of the transmissibility curve. The viscoelastic dynamic damping nature of the elastomer was also studied by analyzing the force-displacement hysteresis graphs. The results show that MR effect increases with the increase in magnetic field as well as carbonyl iron powder particle concentration. It is observed that softer matrix material produces more MR effect. A maximum of 125% improvement in the loss factor is observed for the MRE with 25% carbonyl iron volume concentration. FEMM simulation shows that as carbonyl iron particle distribution becomes denser, MR effect is improved. FEMM analysis also reveals that if the distance between the adjacent iron particles are reduced from 20 μm to 10 μm, a 40% increase in stored energy is observed.

高竖向承载力MRE支座的试验和力学模型研究

磁流变弹性体(magneto-rheological elastomer,MRE)隔震支座竖向承载力低,竖向荷载对支座力学性能影响显著,限制了MRE支座的工程应用。通过增设竖向连杆承担竖向荷载,永磁铁提供恒定磁场,研发了MRE片与钢板交替叠合、剪切刚度双向可调的隔震支座。采用有限元方法分析了MRE片厚度、永磁铁厚度和永磁铁放置位置等对支座磁路的影响,设计制作了芯体直径为60 mm,由26片MRE和25片钢板组成的MRE叠层隔震支座。开展了不同频率、振幅、电流大小和配重下支座力学性能试验,基于试验结果,采用粒子群算法对支座的Bouc-Wen模型进行参数识别,建立了支座的Bouc-Wen模型。结果表明,所设计的MRE支座竖向承载力高,力学性能稳定,Bouc-Wen模型可以准确地描述支座的滞回特性,拟合数据与试验结果吻合较好。

MRE耗能阻尼器力学性能及半主动控制分析

根据磁流变弹性体(magnetorheological elastomer,简称MRE)的可调力学特性提出了基于MRE的新型耗能阻尼器,并对制备完成的硅橡胶基磁流变弹性体及阻尼器分别进行力学性能试验。利用Matlab/Simulink对各层均装有MRE阻尼器的7层框架结构进行建模仿真分析,将被动控制与基于半主动控制策略的经典最优控制和序列最优控制进行比较。力学测试结果表明:MRE在0~500 mT磁感应强度下其剪切模量变化值达到132.43 kPa,磁流变效应约提高274%;增大加载幅值和加载速率,均能提高MRE阻尼器的力学性能;对阻尼器施加电流激励,在0~10 A增大过程中其等效刚度和阻尼可以实现连续可调。仿真结果表明:基于MRE阻尼器的半主动控制系统可以有效减小结构在地震作用下的响应,3种控制均能对结构动力响应起到良好的控制效果,其中序列最优控制算法的控制效果最为显著且精确度更高;系统在实际测试中需考虑多方面因素影响,尽可能减小误差。

Magneto-rheological elastomer (MRE) based composite structures for micro-vibration control

Magneto-rheological elastomers （MILEs） are used to construct composite structures for micro-vibration control of equipment under stochastic support-motion excitations. The dynamic behavior of MREs as a smart viscoelastic material is characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. Frequency-domain solution methods for stochastic micro-vibration response analysis of the MRE-based structural systems are developed to derive the system frequency-response function matrices and the expressions of the velocity response spectrum. With these equations, the root-mean-square （RMS） velocity responses in terms of the one-third octave frequency band spectrum can be calculated. Further, the optimization problem of the complex moduli of the MRE cores is defined by minimizing the velocity response spectra and the RMS velocity responses through altering the applied magnetic fields. Simulation results illustrate the influences of MRE parameters on the RMS velocity responses and the high response reduction capacities of the MRE-based structures. In addition, the developed frequency-domain analysis methods are applicable to sandwich beam structures with arbitrary cores characterized by complex shear moduli under stochastic excitations described by power spectral density functions, and are valid for a wide frequency range.

大部件装配中的MRE被动柔顺装置研究

随着我国航天制造领域智能化要求的不断提升,利用工业机器人实现大部件的柔顺辅助装配对实现航天器的智能制造具有重要意义。然而在进行大部件的高精度装配时,机器人易受限于本体性能而难以弥补物理上的机械设计误差。据此,基于磁流变弹性体(Magnetorheological Elastomer,MRE)设计了一种可变刚度的被动柔顺装置置于机器人末端,并对其进行了仿真及实验测试,结果表明,升高通入电流可提高装置刚度,且装置在1 A电流差下的位移差约为20%,适配柔顺辅助装配的不同过程。

Magnetorheological elastomer and smartphone enable microfluidic biosensing of foodborne pathogen

Rapid detection of foodborne pathogens is crucial to prevent the outbreaks of foodborne diseases.In this work,we proposed a novel microfluidic biosensor based on magnetorheological elastomer(MRE)and smartphone.First,micropump and microvalves were constructed by deforming the MRE under magnetic actuation and integrated into the microfluidic biosensor for fluidic control.Then,the micropump was used to deliver immune porous gold@platinum nanocatalysts(Au@PtNCs),bacterial sample,and immunomagnetic nanoparticles(MNPs)into a micromixer,where they were mixed,incubated and magnetically separated to obtain the Au@PtNC-bacteria-MNP complexes.After 3,3',5,5'-tetramethylbenzidine and hydrogen peroxide were injected and catalyzed by the Au@PtNCs,smartphone was used to measure the color of the catalysate for quantitative analysis of target bacteria.Under optimal conditions,this biosensor could detect Salmonella typhimurium quantitatively and automatically in 1 h with a linear detection range of 8.0×10^(1) CFU/mL to 8.0×10^(4) CFU/mL and a detection limit of 62 CFU/mL.The microfluidic biosensor was compact in size,simple to use,and efficient for detection,and might be used for in-field screening of foodborne pathogens to prevent food poisoning.

磁流变弹性体及其振动控制应用综述

磁流变弹性体是将磁性颗粒(微米级)分散到聚合物弹性体中制备而成的一种磁控智能材料,其不仅拥有颗粒增强复合材料的优异力学特性,还具备迅速、连续且可逆的磁控特性,在智能传感、电磁屏蔽及缓冲减振等领域具有广泛的前景。为了促进磁流变弹性体及其振动控制技术的发展,综述了磁流变弹性体的材料组成,制备方法。总结了磁流变弹性体在振动控制领域的应用现状及对应用前景进行了展望。