Journal of Intelligent Material Systems and Structures

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

In order to investigate the magnetic-induced friction properties of magneto-rheological elastomers, isotropic and anisotropic magneto-rheological elastomers are fabricated, tribological testing setup is built, and the friction experiment is carried out. The experimental results show that the isotropic magneto-rheological elastomer has a decreasing friction coefficient with magnetic field applied, which is also affected by particle volume fraction. The influence of magnetic field on friction coefficient of the anisotropic magneto-rheological elastomers is not monotonic. The experimental results also show that the friction coefficient of magneto-rheological elastomers decreases with the increase in load for both isotropic and anisotropic magneto-rheological elastomers in most circumstances. The volume fraction of carbonyl iron powders being around 10% is the best for magneto-rheological elastomers in tuning friction. The tunable range of friction could be as high as 25% under a magnetic field of 0.25 T. Images of the magneto-rheological elastomer interfaces show that the surface roughness is reduced by about 20.7% when a magnetic field of 0.5 T is applied. The aggregation phenomenon is observed on the surface of the magneto-rheological elastomer under a magnetic field. On the basis of three-dimensional surface topography, a preliminary model for the aggregation of micro asperities on the surface of the magneto-rheological elastomer is built to interpret the influence of the magnetic field on the tribological properties of magneto-rheological elastomers.

In this article, we proposed a study on the performance of a magneto-rheological elastomer isolator for the vibration isolation of a scaled bridge system. Based on dimensionless analysis of dynamic characteristics of real bridge system, the vibration acceleration and displacement of bridge deck are considered as evaluation indexes. According to the parameters of a scale model for the three-span bridge, a scaled magneto-rheological elastomer isolator prototype is designed and manufactured, and a small-scale test bench is set up to test the performance of magneto-rheological elastomer device for bridge vibration control. The experimental study shows that the bench testing results are consistent with that of theoretical model in terms of the vibration displacement and acceleration. Therefore, the small-scale study of bridge vibration system with magneto-rheological elastomer isolator based on similarity theory reveals the performance of a real bridge system. It shows that the scaled platform can model the vibration performance of a three-span bridge, which provides a fundamental understanding of the MRE isolator in the applications for the full-scale bridge system.

This work is focused on the study of the dynamic behavior of thick magnetorheological elastomers at high frequencies. Experimental and theoretical studies are conducted to investigate the dynamic shear properties of magnetorheological elastomers which are affected by increasing the thickness, as well as the percentage of iron particles contained in magnetorheological elastomers. A double-shear test setup is designed and built to test the magnetorheological elastomer samples over a range of frequencies from 200 to 800 Hz. The results demonstrate that the thickness of magnetorheological elastomer significantly affects the material properties in the off-state, that is, when no magnetic field is applied. However, for the on-state, when the material is activated by a magnetic field, the thickness of the sample does not show a significant effect on the change in storage modulus induced by a magnetic field. The theoretical analysis includes a macro-mechanical model for the storage modulus and loss modulus of magnetorheological elastomer as a function of thickness, percentage of iron particles, and applied magnetic field. Comparisons between the theoretical and experimental results show that the model reasonably predicts the dynamic behavior of thick magnetorheological elastomers.

The resonance shift property of magnetorheological elastomer is important for developing adaptive absorbers. However, it is well-known that passive nonlinear absorbers have wider effective frequency bandwidths. This article combines these two characteristics in order to develop a hybrid magnetorheological elastomer absorber which can shift its natural frequency and has a wider absorption bandwidth under each constant current. The adaptability and nonlinearity were fully verified experimentally. Afterwards, the absorption ability of the hybrid magnetorheological elastomer absorber was investigated and analyzed. The results show that the effective bandwidth of this absorber is broadened under certain levels of current than linear absorber, and this is caused by the presence of nonlinearity; and the adaptability induced by the magnetorheological elastomer undoubtedly empowers the absorber possible to trace the excitation frequency changing in real time. A short-time Fourier transform was finally used to control the magnetorheological elastomer absorber to verify its controllability, showing that an optimal absorption transmissibility was achieved by the controlled hybrid absorber.

Magnetorheological elastomer is a smart magnetic-control polymer material. The aim of this work is to study the stress relaxation behavior of magnetorheological elastomer and expected to improve the anti-stress-relaxation property of magnetorheological elastomer. As a consequence, in this article, we developed an excellent magnetorheological elastomer based on the polyurethane/epoxy interpenetrating polymer networks matrix. The influences of constant strain level, matrix, magnetic field, and temperature on the stress relaxation behavior of magnetorheological elastomer were carefully measured. As expected, results suggested that the incorporation of interpenetrating polymer networks improved the anti-stress-relaxation property of magnetorheological elastomer. In addition, results revealed that the stress relaxation behavior of magnetorheological elastomer was highly dependent on magnetic field and temperature. In order to obtain a deeper insight into the influence mechanism of matrix and magnetic field, the power law model and stretched-exponential Kohlrausch equation were used to fit the experimental relaxation curves. Results showed that the experimental curves fitted well with these theoretical models. The influences of content of epoxy and magnetic field on fitting parameters were discussed, and relevant physical mechanism was proposed to explain it qualitatively.

The conflict requirement between high-speed stability and curving trafficability has been always a critical issue of train. This article proposed an innovative stiffness variable magnetorheological elastomer rubber joint, which contains two sets of electromagnetic coil, magnetorheological elastomer, and three iron flanks to overcome the conflict requirement. To characterize the proposed magnetorheological elastomer rubber joint, an MTS machine was used to test the field-dependent property, the amplitude-dependent performance, and the frequency-dependent response. The test results verified the stiffness variation capability of the proposed magnetorheological elastomer rubber joint. After the characterization, the magnetorheological elastomer rubber joint was then embedded onto a train model. In the simulation, different curve tracks and different train speeds were simulated to evaluate the effectiveness of the magnetorheological elastomer rubber joint on reducing the angle of attack. Additionally, the critical speeds of the train models were tested and compared when the magnetorheological elastomer rubber joint was working in softened and stiffened mode, respectively. The simulation results demonstrated that the magnetorheological elastomer rubber joint can offer soft and hard wheelset positioning stiffness under different requirements so that both the high-speed stability and curve trafficability of the train can be guaranteed.

The use of a patterned electrode on one side only is expected to be a suitable solution for omitting the wiring to the movable electrode using electrorheological gel. Electrorheological gel is a functional material that changes the force absorbance and frictional force characteristics of its surface in response to the magnitude of an applied electric field. One problem in both the design and the application of electrorheological gels is the wiring of the electrodes that must sandwich the electrorheological gel. Thus, a one-side patterned electrode can be a desirable solution. We investigated the shear stress produced by electrorheological gel applied to such a patterned electrode during rotational and translational motion. Variation of the material of the opposing part reveals that the mechanical and electric characteristics of the electrode meaningfully affect the experienced shear stress.

Core/shell-like structured nanocomposites of polypyrrole and sodium alginate were synthesized through an in situ oxidative polymerization. The morphology of the samples was studied by scanning electron microscopy and transmission electron microscopy. The structure and chemical components were investigated by X-ray diffraction, Fourier-transform infrared spectroscopy, and Raman spectra. These polypyrrole and sodium alginate nanocomposites exhibited better thermal stability than that of polypyrrole as confirmed by thermogravimetric analyzer. Afterward, the electrorheological characteristics of these as-obtained samples dispersed in silicone oil were examined by a rotational rheometer. The typical electro-responsive properties were observed under an external electric field. Furthermore, compared with polypyrrole, the core/shell-like structured polypyrrole and sodium alginate nanocomposites exhibited enhanced electrorheological behaviors, providing potential application in smart automatic control systems.

In this article, we present the results of creation of fillers for electrosensitive rheological fluids, the rheological characteristics of which depend only on the electric field strength and are independent of the change in temperature. The material of the electrorheological fluid filler, nanosized titanium dioxide modified by aluminum cation, was synthesized by the sol-gel method. The rheological properties of electrorheological fluids on the base of synthetic MOBIL oil with TiO₂ particles alloyed with 7, 9, and 12 mol% of Al were investigated in the electric field strength varying from 0 to 3.5 kV/mm. The shear stress (τ > τ₀) of electrorheological fluids was determined by a Physica MCR-301 rheometer. The highest shear stress at T = 20°C was reached in electrorheological fluid with TiO₂ particles alloyed with 12 mol% of Al. Comparison of shear stress for electrorheological fluids with TiO₂ particles (12 mol% Al) annealed at T_an = 600°C, 700°C, and 800°C shows that the highest result was obtained for electrorheological fluid-3 (T_an = 700°C). The most stable values of shear stress in the temperature range from 5°C to 80°C were obtained for electrorheological fluid with TiO₂ particles alloyed with 12 mol% Al annealed at T_an = 800°C.

The high price and less content of current Braille displays keep most of visually impaired persons from using them. The compact arrangement of Braille dots regulated by Braille standard presents a rigid limitation to develop a full-page Braille display. Electrorheological valve gives a possibility to meet these severe demands, and its pressure drop is a key parameter to design a full-page Braille display. A giant electrorheological valve in DC field and square waveform AC field with different frequencies was investigated. It was shown that the pressure drop of valve increases with the electric field strength, and decreases with increasing frequency of square waveform AC field. The pressure drop of the giant electrorheological valve is high enough for the purpose in application of a full-page Braille display. The results also show that only square waveform AC field with low frequency can provide higher pressure drops. A forcing flow of giant electrorheological fluids in channel of valve may be a solution of solving the aggregations of nanoparticles on the electrodes.

This article attempts to clarify the question of what the essential difference between the optimal and “clipped-optimal” control is that the Hamilton–Jacobi–Bellman or Hamilton–Jacobi–Isaacs partial differential equation is linear or nonlinear. An adaptive optimal control based on policy iteration to the constrained semi-active vehicle suspension system with a magnetorheological damper is presented. The problem of improving the optimal performance of semi-active control suspension system is converted to L₂-gain optimal control problem. A two-player policy iteration scheme is employed to solve the Hamilton–Jacobi–Isaacs equation by use of neural networks to approximate optimal policies and value functions in the admissible global region. Simulation results demonstrate that the adaptive optimal controlled semi-active vehicle suspension system outperforms greater than that of the clipped-LQR controlled.

This article reports means to significantly enhance the adaptation of static and dynamic properties using magnetorheological elastomers and demonstrates the enhancements experimentally. The tunability of traditional magnetorheological elastomers is limited by magnetic field strength and intrinsic magnetic–elastic coupling. This contrasts with recent efforts that have revealed large static and dynamic properties change in elastomeric metamaterials via exploiting internal void architectures and collapse mechanisms, although design guidelines have not been developed to adapt properties in real-time. Considering these benchmark efforts, this research integrates concepts from topologically controlled metamaterials and active magnetorheological elastomers to create and study magnetoelastic metamaterials that mutually leverage applied magnetic fields and reconfiguration of internal architectures to achieve real-time tuning of magnetoelastic metamaterial properties across orders of magnitude. Following detailed descriptions of the manufacturing procedures of magnetoelastic metamaterials, this article describes experiments that characterize the static and dynamic properties adaptation. It is found that by the new integration of internal collapse mechanisms and applied magnetic fields, magnetoelastic metamaterials can be reversibly switched from near-zero to approximately 10 kN/m in one-dimensional static stiffness and tailored to double or halve resonant frequencies for dynamic properties modulation. These ideas may fuel new research where geometry, magnetic microstructure, and structural design intersect, to advance state-of-the-art utilization of magnetorheological elastomers.

In this article, an existing railway vehicle is modelled as a full-scale nine-degree-of-freedom system considering lateral, yaw and roll motions of the car body and the front and rear bogies. Moreover, nonlinear stiffness and damping functions of passive suspension systems are extracted from experimental data. In order to improve the ride quality of the rail vehicle, a magnetorheological damper is integrated into the secondary lateral suspension system. Parameters of the magnetorheological damper depend on current, amplitude and frequency of excitations. Tracks with five different types of irregularity are considered for train speeds of 160 and 200 km/h. The track input is given to the multibody system in VI-Rail software and the wheel response is generated. The wheel motions are input to the mathematical model represented in MATLAB/Simulink. Four types of analyses are performed with (1) conventional passive lateral damper, (2) semi-active low, (3) semi-active high and (4) semi-active controlled MR lateral damper in the secondary suspension. Disturbance rejection and force-tracking damper controller algorithms were applied to control the desired force to reduce the lateral vibration. The results clearly imply that the proposed semi-active suspension system improves the vibration attenuation and ride quality of the vehicle.