Magneto-hyper-viscoelastic simulation of MRE under uniaxial compressive loading

Magnetorheological elastomers (MREs) have excellent magnetic-control mechanical properties, which ensures its great engineering application value in the field of vibration control. In this paper, the iron–nickel foam (INF) reinforced MREs with excellent magnetorheological (MR) properties were developed. The soft magnetic properties and three-dimensional (3D) foam structure of INF ensure an effective enhancement on the magnetic-control mechanical properties of MRE. The static and dynamic mechanical properties of the MRE were tested based on a parallel plate rheometer. Among them, static compression tests were carried out to study the static mechanical properties of MREs. The test results showed that INF reinforced MREs have excellent magneto-induced compression modulus. The effects of magnetic field, shear strain, and frequency on the dynamic mechanical properties of MREs have studied by the dynamic oscillatory shear tests. The test results revealed that the MRE has excellent MR properties under small strain. In addition, several successive tests were conducted to evaluate the response behavior under transient magnetic field and hysteresis properties of MREs under periodic magnetic field, and no obvious hysteresis in the repeated test curves have been observed. The INF reinforced MRE studied in this paper has potential application prospects in the field of micro-vibration control.

Compared with most dynamic tests, point load test is widely used in engineering practice because of its wide requirements for test conditions. In offshore mining engineering, the surrounding rock is affected by dynamic load impact and corrosion of various aqueous solutions for a long time. Therefore, it is of great significance to study the influence of hydrochemical corrosion on dynamic mechanical properties of rock to ensure the stability of surrounding rock. In this paper, a large number of dynamic point load and dynamic uniaxial compression tests were carried out on the granite mined from a large mine by using the Split Hopkinson pressure bar test device after the corrosion of pH values of 2, 5, and 7 solutions, respectively. Based on the energy theory, the crushing energy consumption in the test process is analyzed, and finally the fitting formula of the dynamic compressive strength and the crushing energy consumption in the dynamic point load test is obtained through fitting analysis. The results show that when the crushing energy consumption in the dynamic point load test is used to estimate the dynamic compressive strength, a certain crushing energy consumption (the final value of this test is 70 J in this paper) is more accurate, and it can estimate the dynamic compressive strength under various corrosion conditions under this crushing energy consumption. However, with the change of crushing energy consumption in the dynamic point load test, this transformation relationship is no longer accurate, and it is necessary to modify this transformation relationship with corrosion condition as the influencing factor. This conclusion can provide reference for obtaining the dynamic compressive strength of rocks under different corrosion conditions in engineering field in the future.

The material testing machine and the split Hopkinson pressure bar (SHPB) were adopted, respectively, to conduct the static and dynamic compression tests on granite specimens heat treated by different temperatures. The effects of strain rate and heat-treatment temperature on the mechanism of energy evolution of the specimen during deformation and failure process were studied. The results show a significant strain rate effect on the granite, with the energy dissipation density increasing with increasing impact velocity (or strain rate), regardless of the treatment temperature. The specimens heat treated at 300 °C and 700 °C have the minimum and maximum energy dissipation densities, respectively. The specimen in the SHPB tests easily broke into pieces or even powder; while under static compression, only macroscopic fracture surfaces and spalling phenomenon on the specimen were detected. The energy dissipation density is inversely proportional to the compressive strength of the specimen. The rate of energy dissipation change is defined, which can be used to identify the stages in the deformation process of rock and to determine the position of the failure point in the stress-strain curve. For both the dynamic and static compression tests, the value of energy utilization ratio is relatively low, with a maximum value of about 35%.

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.

Modified silane-coated carbonyl iron/natural rubber composite elastomer and its magnetorheological performance

A review on magneto-mechanical characterizations of magnetorheological elastomers

The primary goal of this work is to test and model the magnetorheological (MR) properties of the isotropic magnetorheological elastomers (MREs) under the coupled static–dynamic compressive loads. Isotropic MREs with different contents of magnetic particles were fabricated based on the silicone elastomer. In order to apply the controllable magnetic field to the MREs and directly measure the viscoelastic force of the deformed MREs during the dynamic tests, an electromagnet with a magnetic flux density of up to 0.9 T was developed and integrated into an electric dynamic test system. The stress–strain hysteresis loops of the produced MREs were experimentally characterized under the dynamic compressive loads coupled with different static pre-strains. Effects of particle content, strain amplitude, static pre-strain and load frequency on the MR properties of the MREs were examined in terms of the characteristics of the hysteresis loops, as well as the MR effects in the storage modulus, loss modulus and pre-stress. The results revealed that irrespective of the applied magnetic field, the deformation behavior of the produced MREs was in an approximate linear viscoelastic state when the strain amplitude was less than 7.5%. Both the absolute and relative MR effects increase with the increasing particle content, and decrease with the increasing strain amplitude. Only the absolute MR effect increases with the increasing pre-strain. While varying the load frequency has almost no effect on the MR effect of the MREs. Furthermore, two empirical models were proposed respectively for predicting the storage modulus and loss modulus of the MREs as functions of the magnetic flux density, particle content, strain amplitude, pre-strain and load frequency. The graphical comparison and quantitative evaluation show that the proposed models can give effective predictions of the storage and loss moduli of the produced MREs under the applied load conditions in this work.

A Magnetorheological Elastomer (MRE) can be categorized as a smart material as it can respond when it is subjected to a magnetic field against itself. Shrinking and changing shape in MRE is due to the displacement of magnetic particle in the MRE matrix. However, the lack of understanding of the magnetic flow through magnetic particle in the elastomer matrix causes difficulties to improve the best MRE matrix type and a magnetic circuit for use in MRE devices. In this paper, a finite element magnetic method (FEMM) software has been used to investigate and to study the effect of the magnetic flow when the angle of the magnetic particle in the MRE changed. The analysis was conducted in two-dimensional cross-section (axisymmetric type) with two magnetic particles in the elastomer matrix and the magnetic core. The result shows by changing the angle of the magnetic particle, the value of the magnetic flow and magnetic flux density also change. As a conclusion, the magnetic particle arrangement in the elastomer matrix plays a vital role in designing the MRE matrix layer and MRE device. By understanding the magnetic flow through the magnetic particle, one can improve the method in the preparation of MRE matrix and MRE magnetics circuit.

This study presents the dynamic numerical model of magneto-rheological elastomers (MREs) along with the dynamic testing of the material under various loading conditions. Primarily the loading in shear mode is considered in this study because many civil engineering structures are subjected to shear loading. Experimental tests were carried out in order to characterize the dynamic behavior of MREs. A test setup was designed and fabricated to load the MRE samples in shear mode with varying magnetic fields. A series of shear tests of MRE samples were performed under various magnetic field values, amplitudes and frequencies of loading. The test results show that the material stiffness is increased with increasing magnetic field and loading frequency within the ranges of the magnetic field and exciting frequency considered in this work. Based on the experimental results, a dynamic model was developed to capture the dynamic behavior of the MRE.

Magnetorheological Elastomer (MRE) is a type of smart composite material consisting of a polymer matrix embedded with ferromagnetic particles. In the presence of an external magnetic field, its mechanical properties, such as stiffness, changes make it attractive in vibration isolation applications. Unwanted vibration in machines can cause severe damage and machine breakdown. In Qatar, the extraction of the natural gas from the ground requires sophisticated drilling machines. In this work, a semi-active vibration isolator using MRE is proposed for a potential application in a drilling system to isolate the torsional vibration. MRE was fabricated with a 35% mass fraction (MF) consisting of silicon rubber and iron particles. It was fitted with aluminum couplers and attached to the shaft (drill string) to study its efficiency in vibration isolation under a magnetic field. Two tests were conducted on the drilling prototype setup used in this work; the first test was a hammer impact test. The torsional transfer function TTF analysis showed that the system's natural frequency has shifted from 13.9 Hz to 17.5 Hz by the influence of increasing magnetic field around the MRE. The results showed that the continuous rotational vibration amplitude of the prototype is attenuated by more than 40%.

Magnetorheological elastomers (MREs) are polymers reinforced by ferromagnetic particles that show magnetic dependent behavior. Mixing MREs with reinforcing fibers can create a new class of material so-called “MRE composites, MRECs” with additional functionalities and properties. Here, using a Generalized Maxwell model, we proposed a new magnetic-dependent rheological model by considering the hysteresis phenomenon for MREs to predict the dynamic damping responses of MREC plates reinforced by fibers in the frequency domain. We also investigated the influence of magnetic flux intensity, the volume fraction of the fiber, the orientation angle of the fibers, the number of layers, as well as the fiber-to-matrix stiffness ratio on the natural frequency, loss factor, and mode shapes of MRECs plates. Our results suggest that homogenously increasing the elastic properties of the MRECs through the spatial distribution of fibers and changing the fiber-to-matrix stiffness ratio can effectively tailor the dynamic properties of MRECs. Tailoring these properties can provide additional freedom for the fabrication of 4D-printed MRE-based composites.

This paper presents a numerical investigation of a smart base isolation system employing magneto-rheological (MR) elastomers or an MR elastomer-based base isolation system. MR elastomers are a new class of smart materials whose elastic modulus or stiffness can be adjusted depending on the magnitude of the applied magnetic field. Hence, they can be used as controllable stiffness elements in engineering systems. The primary goal of this study is to investigate the dynamic performance of the smart base-isolation in mitigating excessive vibrations of a building structure under earthquake loadings. To this end, a five-story shear building model coupled with a smart base-isolation is developed. Using this model, a series of numerical simulations is performed to evaluate the effectiveness of the MR elastomer-based base isolation system under several historic seismic excitations. The results show that the proposed base isolation system outperform the conventional passive-type base isolation system in reducing the responses of the building structure for all seismic excitations considered in this study.

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.

Magnetorheological (MR) materials are a group of smart materials used in new technologies with controlled reliability. The development of these materials is expanding, starting from MR fluids, elastomers, grease, and gel. This large number of material types further expands the various applications of MR materials as a creative technology to support performance enhancement. For example, MR fluid is used to improve the performance of shock absorbers such as vehicle suspension, the damping of building structures, and polishing of the workpiece. MR elastomers are used for engine mounting, insulation base, and many other applications with intelligent material properties such as stiffness controllability. However, there are still complexities in the practical implementation of the control system beyond reliability. Many previous studies have focused on the performance improvement and reliability of MR materials as smart materials for application devices and systems. In this review article, the specific discussion related to vibration control strategies in MR material-based systems was thoroughly investigated. To discuss this point, many MR applications including transportation system and vibration isolation were adopted using different types of control strategies. Many different control strategies that have been used for MR applications such as fuzzy logic control, optimal control, and skyhook control are discussed in-depth in terms of the inherent control characteristics of merits and demerits.

Magnetorheological elastomers (MREs) are intelligent materials that exhibit changes in their properties when exposed to a magnetic field. By applying a magnetic field during the curing process, MRE can be made anisotropic. This study focuses on optimizing the fabrication process parameters using the design of an experimental approach, namely the Taguchi method. The parameters to be optimized for MRE fabrication include the number of coil turns, coil diameter, curing current, and curing time. Twenty-five sets of anisotropic MRE were fabricated and subjected to drop impact testing to evaluate their impact absorption capability. The results were further examined for a more comprehensive analysis using the signal-to-noise ratio, analysis of means, and analysis of variance. This rigorous examination aimed to pinpoint the optimal parameters and the key factors influencing the fabrication of the MRE. From the analysis result, it can be seen that the number of coil turns contributed to 63.36% of the entire MRE fabrication process. Furthermore, a well-defined composition for the MRE was identified, consisting of 200 coil turns, a coil diameter of 1.0 mm, an applied current of 1.2 A, and a curing time of 20 min.