nan Ubaidillah

A high performance magnetorheological valve with a meandering flow path

The huge developments in the field of magnetorheological (MR) fluid-based devices will have a great influence on the future of mechatronic applications due to the ease of interfacing between electronic controls and the mechanical components that they provide. Among various MR fluid-based devices, an MR valve would be particularly significant for the development of other devices, if it could be successfully achieved. One of the most challenging obstacles to MR valve development is the difficulty of achieving device miniaturization while, at the same time, improving the achievable performance. This study demonstrates a novel design for an MR valve, using the meandering flow path approach in order to increase the effective area so that the MR fluid can be regulated within a small-sized valve. The meandering flow path is formed by combining multiple annular, radial and orifice flow channels. In order to analyze the valve performance, a mathematical model of the proposed MR valve is derived and combined with numerical simulation using the finite element method, with the intention of predicting the achievable pressure drop that can be generated by the valve. The predicted MR valve performances are then experimentally evaluated using an oscillation-disturbed bypass hydraulic cylinder. The simulation results show that the proposed MR valve design could yield substantial pressure drop improvement, which is confirmed by the experiment.

A new class of magnetorheological elastomers based on waste tire rubber and the characterization of their properties

This paper proposes a new type of magnetorheological elastomer (MRE) using rubber from waste tires and describes its performance characteristics. In this work, scrap tires were utilized as a primary matrix for the MRE without incorporation of virgin elastomers. The synthesis of the scrap tire based MRE adopted a high-temperature high-pressure sintering technique to achieve the reclaiming of vulcanized rubber. The material properties of the MRE samples were investigated through physical and viscoelastic examinations. The physical tests confirmed several material characteristics - microstructure, magnetic, and thermal properties-while the viscoelastic examination was conducted with a laboratory-made dynamic compression apparatus. It was observed from the viscoelastic examination that the proposed MRE has magnetic-field-dependent properties of the storage modulus, loss modulus, and loss tangent at different excitation frequencies and strain amplitudes. Specifically, the synthesized MRE showed a high zero field modulus, a reasonable MR effect under maximum applied current, and remarkable damping properties.

Development of a modular MR valve using meandering flow path structure

The extensive development of the magnetorheological (MR) valve has successfully introduced a new high-performance compact-class MR valve using a meandering flow path structure. Aside from the performance improvement, in real applications, the ease of performance adjustment also needs to be improved. This study focused on the development of a new design of a modular MR valve using a meandering flow path to improve the adjustability of the valve performance. The approach is proposed based on the high-performance advantages of a meandering flow path structure, while at the same time utilizing the benefit of the modular structure in terms of performance flexibility. In order to evaluate the performance of the modular structure, the analytical assessment was conducted for three different module stages: the single-stage module, the double-stage module, and triple-stage module. To predict the strength of the magnetic field in the effective area, the magnetic simulation was conducted through an open-source software called the FEMM (Finite Element Method Magnetics). The quasi-steady mathematical model of the proposed valve was also derived to conduct the analytical assessment as well as to predict the valve performance. In order to validate the simulation results, the prototypes of the proposed valve are experimentally tested with the aid of the hydraulic cylinder on a dynamic test machine. The results of the MR valve assessment from both the simulation and experimental test demonstrated that the pressure drop rating of the meandering type MR valve can be easily modified using modular structure by changing the number of module stages.

Rheological properties of isotropic magnetorheological elastomers featuring an epoxidized natural rubber

This study presents principal field-dependent rheological properties of magnetorheological elastomers (MREs) in which an epoxidized natural rubber (ENR) is adopted as a matrix (in short, we call it ENR-based MREs). The isotropic ENR-based MRE samples are fabricated by mixing the ENR compound with carbonyl iron particles (CIPs) with different weight percentages. The morphological properties of the samples are firstly analysed using the microstructure assessment. The influences of the magnetic field on the viscoelastic properties of ENR-based MREs are then examined through the dynamic test under various excitation frequencies. The microstructure of MRE samples exhibits a homogeneous distribution of CIPs in the ENR matrix. The dramatic increment of storage modulus, loss modulus and loss tangent of the ENR-based MREs are also observed from the field-dependent rheological test. This directly demonstrates that the stiffness and damping properties of the samples can be adjusted by the magnetic field. It is also seen that the CIP content, exciting frequency and the magnetic field essentially influence the dynamic properties of the ENR-based MREs. The strong correlation between the magnetization and the magneto-induced storage modulus could be used as a useful guidance in synthesizing the ENR-based MREs for certain applications.

The Field-Dependent Rheological Properties of Magnetorheological Grease Based on Carbonyl-Iron-Particles

This paper presents dynamic viscoelastic properties of magnetorheological (MR) grease under variation of magnetic fields and magnetic particle fractions. The tests to discern the field-dependent properties are undertaken using both rotational and oscillatory shear rheometers. As a first step, the MR grease is developed by dispersing the carbonyl iron (CI) particles into grease medium with a mechanical stirrer. Experimental data are obtained by changing the magnetic field from 0 to 0.7 T at room temperature of 25 °C. It is found that a strong Payne effect limits the linear viscoelastic region of MR grease at strains above 0.1%. The results exhibit a high dynamic yield stress which is equivalent to Bingham plastic rheological model, and show relatively good MR effect at high shear rate of 2000 s-1. In addition, high dispersion of the magnetic particles and good thermal properties are proven. The results presented in this work directly indicate that MR grease is a smart material candidate that could be widely applicable to various fields including vibration control.

Fabrication and investigation on field-dependent properties of natural rubber based magneto-rheological elastomer isolator

This study presents a laminated magnetorheological elastomer (MRE) isolator which applies to vibration control in practice. The proposed isolator is fabricated with multilayer MRE sheets associated with the natural rubber (NR) as a matrix, and steel plates. The fabricated MRE isolator is then magnetically analysed to achieve high magnetic field intensity which can produce high damping force required for effective vibration control. Subsequently, the NR-based MRE specimen is tested to identify the field-dependent rheological properties such as storage modulus with 60 weight percentage of carbonyl iron particles. It is shown from this test that the MR effect of MRE specimen is quantified to reach up to 120% at 0.8 T. Following the design stage, the electromagnetic simulation using the finite element method magnetic (FEMM) software is carried out for analysing the magnetic flux distribution in the laminated MRE isolator. The laminated MRE isolator is then examined to a series of compression for static and dynamic test under various applied currents using the dynamic fatigue machine and biaxial dynamic testing machine. It is shown that the static compression force is increased by 14.5% under strong magnetic field compared to its off-state. Meanwhile, the dynamic compression test results show that the force increase of the laminated MRE isolator is up to 16% and 7% for low and high frequency respectively. From the results presented in this work, it is demonstrated that the full-scale concept of the MRE isolator can be one of the potential candidates for vibration control applications by tunability of the dynamic stiffness.

Potential applications of magnetorheological elastomers

Magnetorheological elastomer still becomes interested topics among researchers since the rheological properties can be controlled by applying external magnetic field by means of adjustable modulus of elasticity. In this paper, the current application of MRE and related patents will be discussed. Potential application of MRE focused on three main areas. The first is explanation on MRE implementation in vibration cancellation mainly in vehicle system such as active vibration suppression and variable impedance sound absorber. The second explanationfocuses on its potential application on medical devices such as prosthetic device. The third section describes future possible application of MRE based on its tunable properties.Finally, the concluding remarks can be generally stated that MRE still has wide range smart device development and promising more valuable product.

The field-dependent complex modulus of magnetorheological elastomers consisting of sucrose acetate isobutyrate ester

In this work, epoxidized natural rubber-50 magnetorheological elastomer was synthesized using conventional rubber processing. The ester plasticizer sucrose acetate isobutyrate was then incorporated into epoxidized natural rubber-50 to soften the matrix and to improve the relative magnetorheological effect. The influence of sucrose acetate isobutyrate ester on the microstructures and properties of epoxidized natural rubber-50 magnetorheological elastomers were experimentally investigated. It has been identified that the addition of sucrose acetate isobutyrate ester can reduce the viscosity of the matrix and increase the mobility of magnetic particles in a matrix. The elongation of magnetorheological elastomer was increased by 19%, and the tensile strength was reduced by 17% at 10 wt% content of the sucrose acetate isobutyrate ester. It is observed that the employment of sucrose acetate isobutyrate ester enhanced the thermal stability leading to low degradation of the properties of magnetorheological elastomer. In rheology test, both absolute and relative magnetorheological effects were increased by 0.16 MPa and 23%, respectively, with incorporation of the 7.5-wt% sucrose acetate isobutyrate ester. It is also identified that the storage and loss moduli as well as loss factor are increased as the excitation frequency is increased. It is finally concluded that agglomeration issues in isotropic magnetorheological elastomer which degrade performances of magnetorheological elastomer application devices and systems can be resolved by the addition of sucrose acetate isobutyrate ester to epoxidized natural rubber-50 used in this work.

Fabrication and viscoelastic characteristics of waste tire rubber based magnetorheological elastomer

In this study, waste tire rubber (WTR) was successfully converted into magnetorheological (MR) elastomer via high-pressure and high-temperature reclamation. The physical and rheological properties of WTR based MR elastomers were assessed for performance. The revulcanization process was at the absence of magnetic fields. Thus, the magnetizable particles were allowed to distribute randomly. To confirm the particle dispersion in the MR elastomer matrix, an observation by scanning electron microscopy was used. The magnetization saturation and other magnetic properties were obtained through vibrating sample magnetometer. Rheological properties including MR effect were examined under oscillatory loadings in the absence and presence of magnetic fields using rotational rheometer. The WTR based MR elastomer exhibited tunable intrinsic properties under presentation of magnetic fields. The storage and loss modulus, along with the loss factor, changed with increases in frequency and during magnetization. Interestingly, a Payne effect phenomenon was seen in all samples during dynamic swept strain testing. The Payne effect was significantly increased with incremental increases in the magnetic field. This phenomenon was interpreted as the process of formation–destruction–reformation undergone by the internal network chains in the MR elastomers.

An enhancement of mechanical and rheological properties of magnetorheological elastomer with multiwall carbon nanotubes

In this work, a new type of magnetorheological elastomer, which is reinforced by carbon nanotubes, is fabricated and its material properties are experimentally investigated. In order to achieve this goal, as a first step, different types of multiwall carbon nanotubes are incorporated into a series of natural rubber–based magnetorheological elastomers as additives. Several experimental instruments such as X-ray diffractometer, thermogravimetric analysis, and differential scanning calorimetry are utilized. From the test, several salient properties of the proposed magnetorheological elastomer are observed or/and characterized. The results indicate that the interaction between natural rubber–based magnetorheological elastomers and multiwall carbon nanotubes can provide significant improvement in mechanical and rheological properties. More specifically, it is observed that mechanical properties such as tensile strength are enhanced up to 11% by the functionalized multiwall carbon nanotube. It is also found that the field-dependent storage and loss moduli of the proposed magnetorheological elastomer samples are increased compared to magnetorheological elastomer without multiwall carbon nanotube. It is finally identified that magnetorheological efficiency, which indicates force controllability by the magnetic field, of the proposed magnetorheological elastomer samples is consistent with the increased operating frequency. Therefore, it is expected that the results of morphological, thermal, and rheological properties parallel to incorporation of multiwall carbon nanotubes into magnetorheological elastomers are effectively used for proper selection of magnetorheological elastomer applications.