Magneto-induced Modulus Research Articles

Adaptive beam with elastic support based on magnetorheological elastomers for modal modulation and vibration suppression

Owing to the wide modulation capability of their magneto-induced modulus, smart structure-based magnetorheological elastomers (MREs) show great promise for vibration control in numerous engineering applications. In conventional smart structure-based MREs, however, vibration absorption or isolation is mainly used for discrete structural systems, and the requirement for vibration control in continuous structures can limit the application of vibration absorbers and isolators. Therefore, it is necessary to resolve the dynamic properties of the continuous structure to obtain modal information. In this paper, different types of smart beams with adaptive elastic support (AES)-based MREs, containing dual-end elastic support, single-end elastic support, and the combination of a fixed end and an AES at an arbitrary location, are developed to tactically influence the dynamics through magneto-mechanical coupling. A dynamic model of thin-walled beams with AES was established by using the improved Fourier series method (IFSM). The numerical results confirm that the effective suppression bandwidth of the beam with MRE-AES can be shifted as a result of the modal modulation-induced energy transfer from low to high frequencies, which requires a decreasing trend of modal amplitude at the response location as the elastic support stiffness increases. According to the modal analysis, the beams with single-end AES and dual-end AES have a decreasing trend of modal amplitude in the global location as stiffness increases. However, the modal amplitude trend of the beam with a fixed end and an AES is not monotonic at certain locations. The experimental results demonstrate that MRE-AES can effectively attenuate the acceleration responses of the beams with single-end AES and with a fixed end and an AES under harmonic excitation. The resonance peaks in the transmission remarkably shift to higher frequencies with increasing magnetic flux.

Enhancement of Magneto-Induced Modulus by the Combination of Filler and Plasticizer Additives-Based Magnetorheological Elastomer

Filler additive is used to provide superior bonding in rubber matrix to enhance the storage modulus of magnetorheological elastomer (MRE). However, the magneto-induced modulus is reduced as the initial storage modulus increases. Therefore, this paper aims to increase the magneto-induced modulus and maintain the initial storage modulus by combining filler and plasticizer additives. Both types of additives have different functions, where cobalt ferrite (CoFe2O4) is capable of enhancing the maximum storage modulus and silicone oil (SO) reduces the initial storage modulus. Thus, four MRE samples have been fabricated using (a) no additive, (b) CoFe2O4, (c) SO, and (d) a combination of CoFe2O4 and SO. The sample’s hardness and magnetic properties were investigated via Durometer Shore A and Vibrating Sample Magnetometer (VSM), respectively. Furthermore, the rheological properties of MRE samples in terms of storage modulus were investigated upon the frequency and magnetic field sweep using a rheometer. The results demonstrated that the storage modulus of the MRE samples has increased with increasing the oscillation frequency from 0.1 to 50 Hz. Interestingly, the combination of additives has produced the largest value of magneto-induced modulus of 0.90 MPa as compared to other samples. Furthermore, their initial storage modulus was in between samples with SO (lowest) and without additive (highest). Therefore, fundamental knowledge in adding the combination of additives can offer solutions for a wide range of stiffness in MR device applications such as vibration and noise control devices, sensing devices, and actuators.

A macroscopic viscoelastic model of magnetorheological elastomer with different initial particle chain orientation angles based on fractional viscoelasticity

In this paper, a macroscopic viscoelastic modeling method for magnetorheological elastomer (MRE) based on fractional derivative model is presented to describe the dynamic viscoelastic properties of MRE with different initial particle chain orientation angles. The angle between the particle chain and the applied magnetic field is used as an indicator to describe the directionality of the particle chain. MRE samples with different initial inclination angles have been designed and fabricated. The dynamic viscoelastic properties of different MRE samples under shear working mode were measured using a parallel plate rheometer. The dynamic viscoelastic properties of MRE with different initial inclination angles are analyzed under the test conditions of different strain amplitude, frequency and magnetic flux density. The test results show that the initial inclination angle of the particle chain in the MRE has a significant effect on the dynamic viscoelastic properties of the MRE. A polynomial function is used to describe the relationship between the initial particle chain orientation angle and the magneto-induced modulus of MRE. A phenomenological model of magneto-induced modulus is established based on the fractional derivative model. The model parameters are identified using the nonlinear least square method. The predicted values of the model are in good agreement with the experimental results, indicating that the model can well describe the dynamic viscoelastic properties of MRE.

Effect of Mould Orientation on the Field-Dependent Properties of MR Elastomers under Shear Deformation.

In this study, magnetorheological elastomer (MRE) was fabricated using an electromagnetic device with a new configuration mold at the orientation of 0°, 45° and 90°. This new curing concept enhanced the alignment of carbonyl iron particles (CIPs) within the silicone matrix in the presence of silicone oil (SO) during solidifying, by eliminating air gaps to prevent magnetic flux losses. Using a mold made of steel, which is a magnetic material, the mold functions as a guide for concentrated magnetic flux of 0.315 T to pass through the MRE sample. Scanning electron microscopy (SEM) was used to observe the surface morphology of the fabricated MRE samples particularly the alignment of the CIPs. The field-dependent dynamic properties of the MREs were measured using a rheometer. The analysis implied that the effectiveness of the MRE operating under shear deformation with this curing concept provided the highest magneto-induced modulus of 1.01 MPa when a 45° orientation mold is used, with relative magnetorheological (MR) effect value up to 918%, followed by 0° mold orientation with 0.79 MPa magneto-induced modulus and 646% relative MR effect. The high modulus properties offered by this MRE are believed to be potentially useful in industrial applications where a high range of stiffness is required particularly in the shear direction.

Magneto-Sensitive Rubber in a Vehicle Application Context – Exploring the Potential

The application of magneto-sensitive (MS) rubber in a vehicle vibration control area is likely to be expected. This conclusion is based on the following two reasons: the maturity of fabrication of MS rubber which meets the application requirement and the feasibility of the constitutive model of MS rubber that accurately reflects its mechanical performance. Compared with the traditional rubber, small ferromagnetic particles are embedded in the elastomer of MS rubber, leading to a change of mechanical properties when an external magnetic field is applied. Therefore, devices with MS rubber, can be viewed as a semi-active actuator. In this study, MS rubber with a relative high increase in the magneto-induced modulus is fabricated and characterized. Furthermore, a one-dimensional constitutive model to depict the magnetic field-, frequency-, and strain amplitude-dependent dynamic modulus of MS rubber is applied. Finally, simulations of a MS rubber semi-active suspension under a bump and a random ground excitation with different control strategies on a quarter vehicle model are conducted to illustrate the feasibility of the MS rubber in the vehicle vibration control application context.

A Magneto-Hyperelastic Model for Silicone Rubber-Based Isotropic Magnetorheological Elastomer under Quasi-Static Compressive Loading.

A new magneto-hyperelastic model was developed to describe the quasi-static compression behavior of silicone rubber-based isotropic magnetorheological elastomer (MRE) in this work. The magnetization property of MRE was characterized by a vibrating sample magnetometer (VSM), and the quasi-static compression property under different magnetic fields was tested by using a universal testing machine equipped with a magnetic field accessory. Experimental results suggested that the stiffness of the isotropic MRE increased with the magnetic flux density within the tested range. Based on experimental results, a new magneto-hyperelastic model was established by coupling the Ogden hyperelastic model, the magnetization model and the magneto-induced modulus model based on a magnetic dipole theory. The results show that the proposed new model can accurately predict the quasi-static compression property of the isotropic MRE under the tested magnetic flux density and strain ranges using only three model parameters.

The magneto-mechanical properties of off-axis anisotropic magnetorheological elastomers

Off-axis anisotropic magnetorheological (MR) elastomers with different particle chain orientations were investigated. Under the quasi-static and oscillatory shear excitation, the internal structure has significant effects on the mechanical response (initial modulus, magneto-induced modulus and magneto-deformation). The MR effect of the anisotropic MR elastomers could be increased by 127% through simply changing the particle chain orientation by 15° during the fabrication process. The experimental results were verified by using a modified magnetic dipole theoretical model. The magneto-induced torque and normal force of the anisotropic MR elastomers could be significantly affected by the orientation of particle chain, which had great guiding significance for practical applications. Moreover, the MR elastomer composites could achieve complex three-dimensional origami deformations under the external magnetic field. The capability to control the shape morphing of this off-axis anisotropic MR elastomer might open new opportunities for programming complex soft structures.

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.

The impact of CIP content on the field-dependent dynamic viscoelastic properties of MR gels

Magnetorheological (MR) gels are one of the categories of magnetic smart materials, whose mechanical properties changed significantly in the presence of a magnetic field. This paper present dynamic viscoelastic properties of MR gel under various of magnetic flux density and Carbonyl iron powders (CIPs) weight fraction. The test to understand the dynamic rheological properties are carried out using oscillatory shear. Firstly, the MR gels are prepared by dispersing the CIPs into polyurethane (PU) matrix with a mechanical stirrer. Experimental data are obtained by changing the magnetic flux density from 0 mT to 480 mT at room temperature of 25 ℃. The elastic stress of MR gels with different CIPs content was studied under different magnetic flux density in oscillating test environment. The study results display that the elastic stress increases with strengthening extra magnetic flux density and the shape of elastic stress—strain curves are different under various magnetic flux density. Initial modulus, magneto-induced modulus and MR effect of MR gels with different contents of CIPs were obtained by magnetic field scanning. The results show that a higher magnetic-induced storage modulus can be obtained at higher CIPs weight fraction. The critical values and static elastic yield stress of MR gels with different CIPs content are also obtained by shear stress vs shear strain curves at the different magnetic flux density.

Development and dynamic performance test of magnetorheological material for recoil of gun

As a kind of new MR material, MR gel (MRG) can be regard as the analog of MRF, which can overcome the iron particles sedimentation and unstable application of MRF especially in recoil of gun. However, some major parameter of this kind of MRG, such as the initial modulus, magneto-induced shear storage modulus and relative MR effect are relatively small, which cannot meet the need the application in recoil of gun. In this work, an MRG with high magneto-induced shear storage modulus, relative MR effect and suitable initial modulus has been fabricated by controlling the mass fraction of carbonyl iron powder (CIP) under specific crosslinking degree of polyurethane (PU) matrix. And several PU-based MRG composites with the CIP mass fraction of 40, 60, 80% were prepared. The dynamic mechanical property of those MRG samples ware researched through an advanced commercial rheometer. The experimental results indicated that magneto-induced modulus and relative MR effect in sample 2 (containing 60 wt% of CIP) were approximately 2.87 and 2.32 times than sample 1 (containing 40 wt% of CIP), 1.67 and 2.97 times than sample 3 (containing 80 wt% of CIP). Moreover, the samples have good consistency in transient response under the step magnetic field. The high magneto-induced modulus of sample 2 can be mainly attributed to the following point. Appropriate amount of PU polymer chain can reinforce the binding force between CIPs in the chain and better constrained particle motion under magnetic field. It is concluded that this study provides a meaningful way to improve the mechanical properties of MRG and expected to promote the application of MRG in recoil of gun.

Stretchable and magneto-sensitive strain sensor based on silver nanowire-polyurethane sponge enhanced magnetorheological elastomer

This work reported a stretchable, compressible and magneto-sensitive strain sensor based on conductive magnetorheological elastomer (MRE) containing silver nanowires (AgNWs) dip-coated polyurethane sponge, carbonyl iron particles and polydimethylsiloxane (PDMS) matrix. The mechanic-electric-magnetic coupling properties of conductive MRE were investigated and they were significantly influenced by mechanical properties of PDMS matrix and the AgNWs content. By increasing curing agent weight ratio, the cross-linking density of the PDMS increased thus the magneto-induced modulus decreased. The MRE was able to be used in the strain sensors, because its relative resistance variation reached 91.8% and 67.6% when 20% tensile strain and 10% compressive strain were applied. By applying a 428 mT magnetic field, the relative resistance of MRE sensor increased to 200%. Based on the experimental results, a possible mechanism was proposed to investigate the mechanic-electric-magnetic coupling sensing characteristics. Finally, the MRE sensors can be integrated on a shoe to detect the foot motion, demonstrated this material was promising in the intelligent devices like artificial skin, composite electrodes and soft sensor.

Linear magneto-viscoelastic model based on magnetic permeability components for anisotropic magnetorheological elastomers

A new magneto-viscoelastic model is presented for anisotropic magnetorheological elastomers (MREs), which combines the dynamic behaviour and magnetic permeability components. Five samples were synthesised with different particle contents. Dynamic properties were measured using a rheometer equipped with a magnetorheological cell. A four-parameter fractional derivative model was used to describe MRE viscoelasticity in the absence of a magnetic field. The magnetic permeability of each sample was measured with a vibrating sample magnetometer. From experimental measurements of longitudinal and transverse components of the magnetic permeability, the dependency with magnetic field was modelled. The new magneto-induced modulus model proposed in this work is based on the model developed by López-López et al. [19] for magnetorheological fluids, and was adapted for anisotropic MREs. The proposed model includes the longitudinal and transverse components of magnetic permeability, and it is valid for the linear viscoelastic region of anisotropic MREs. The errors between experimental values and the values predicted by the model do not exceed 10%. Hence, a new linear magneto-viscoelastic model for anisotropic MREs is developed, which predicts the effect of magnetic field on the dynamic shear modulus as a function of magnetic field intensity and frequency.

A new three-dimensional magneto-viscoelastic model for isotropic magnetorheological elastomers

In this work, a four-parameter fractional derivative viscoelastic model was developed to describe the dynamic shear behaviour of magnetorheological elastomers (MREs) as a function of the matrix, particle content and magnetic field. The material parameters were obtained from experimental data measured with a Physica MCR 501 rheometer from the Anton Paar Company, equipped with a magnetorheological cell. The synthetised isotropic MRE samples were based on room-temperature vulcanising silicone rubber and spherical carbonyl iron powder micro particles as fillers, and seven volumetric particle contents were studied. The influence of particle contents was included in each parameter of the four-parameter fractional derivative model. The dependency of the storage modulus as a function of an external magnetic field (magnetorheological (MR) effect) was studied, and a dipole–dipole interaction model was used. A new three-dimensional magneto-viscoelastic model was developed to couple the viscoelastic model, the particle-matrix interaction and the magneto-induced modulus model, which predicts the influence of the magnetic field and the particle content in the MR effect of isotropic MREs.

Ni-coated multi-walled carbon nanotubes enhanced the magnetorheological performance of magnetorheological gel

As a kind of new Magnetorheological (MR) material, MR Gel (MRG) can be regarded as the analog of MR fluid (MRF), which can overcome the iron particles sedimentation and unstable application of MRF. Normally, the storage modulus of conventional MRG is relatively small, although it has a very high relative MR effect. Therefore, practical engineering application of conventional MRG has been restricted more or less. In this work, an MRG with high magneto-induced shear storage modulus and excellent relative MR effect has been fabricated by incorporating Ni-coated multi-walled carbon nanotubes (Ni-coated MWCNTs). And several polyurethane-based MRG composites with the addition of Ni-coated MWCNTs were prepared. The dynamic mechanical property of those MRG composites with applying magnetic field is researched through an advanced commercial rheometer. The experimental results indicated that the initial storage modulus and magneto-induced modulus in sample 4 (containing 6 wt% of the Ni-coated MWCNTs) were approximately 4.45 and 2.27 times than that in the sample 1 (without Ni-coated MWCNTs). Moreover, the relative MR effect of sample 4 can reach 3427 %. The high modulus of sample 4 can be mainly attributed to the following points. One is the Ni-coated MWCNTs can be aligned along the direction of the magnetic field within the matrix which provided a better reinforcing efficiency. The other is Ni-coated MWCNTs can be made to form a better bonding between the iron particles and the matrix. It is concluded that this study provides a meaningful way to improve the mechanical properties of MRG and expected to promote the application of MRG in practice.

The prestress-dependent mechanical response of magnetorheological elastomers

Magnetorheological elastomers (MREs) are intelligent materials consisting of a rubber matrix filled with magnetizable particles. In many engineering applications, MREs are usually pre-confined and work with constraint-induced prestress. The prestress can significantly change the mechanical properties of MREs. In this work, the influence of prestress on the mechanical response of MREs is studieds both experimentally and theoretically. The storage modulus as well as the magneto-induced modulus change non-linearly with increasing prestress and three regions can be found in the non-linear change. In the non-full contact region, the MREs present poor mechanical properties at small prestress due to the unevenness of the sample surface. In the full contact region, the MREs are under suitable prestress, thus they present good mechanical properties. In the overload region, the pre-configured microstructure of the MREs is destroyed under the large prestress. Moreover, an analytical model is proposed to study the prestress-dependent mechanical properties of MREs. It is revealed that the prestress can change the inter-particle distance, thus further affecting the mechanical response of MREs.

Effect of Cross-Link Density of the Matrix on the Damping Properties of Magnetorheological Elastomers

The effect of cross-link density of the matrix on the controllable damping properties of magnetorheological elastomers (MREs) has been investigated. MRE samples with different cross-link densities and plasticizer contents were fabricated and their microstructures were observed using an environmental scanning electron microscope (SEM). The dynamic performances of these samples were measured using a modified dynamic mechanical analyzer (DMA). The experimental results indicated the magneto-induced change of loss factor was enhanced by decreasing the cross-link density. The plasticizer and the frequency markedly influenced the magneto-induced change of loss factor when the cross-link density of the matrix was low. In addition, by reducing cross-link density, the magneto-induced modulus and the relative MR effect increased. A mechanism for the magneto-induced change of loss factor was proposed and the analysis implied that the rearrangement of particles is an important influence on controlling the damping prop...

Control of the Damping Properties of Magnetorheological Elastomers by Using Polycaprolactone as a Temperature-Controlling Component

A novel kind of magnetorheological elastomers (MREs) with controllable damping properties was developed in this study. Polycaprolactone (PCL) was selected as the temperature-controllable component in the cis-polybutadiene rubber (BR) based MREs. Several samples with different BR/PCL mass ratio matrixes were prepared. The dynamic performances of the samples, including loss factor, shear storage modulus, and loss modulus, were measured with a rheometer. Differential scanning calorimetry (DSC) analysis indicated that PCL is a phase change material and it can transform from a semicrystalline solid to a liquated soft material by increasing the surrounding temperature above the PCL melting point. Experimental results showed that the damping properties of the MREs can be controlled by varying the PCL weight ratio, the temperature, and the magnetic field. The controlling mechanism was proposed and the influence factors were analyzed. Last, it was also observed that the magneto-induced modulus and the MR effect of the MREs were changed remarkably by the added PCL under different temperatures.

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 magneto-induced 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.