During the last two decades, magnetorheological (MR) materials have attracted a significant amount of attention because of their tremendous potential for engineering applications. This review focuses on the role of various additives in enhancing the magnetic field-dependent rheological characteristics of solid and thixotropic matrice-based MR materials (hereafter referred to as MR solids). Typically, MR solids consist of solid or semi-solid matrices filled with magnetizable particles. However, additives need to be used to improve their performance such as the MR effect. This parameter is typically determined by the field-dependent dynamic modulus. Three different groups of additives would be introduced in the review namely plasticizers, carbon- and chromium-based additives. Compared to particles in the common matrix without a softener, those in matrices with additives which act as matrix softeners will be aligned easier during curing. In fact, the interfaces bonding between matrix-particles would be improved that subsequently enhanced the magnetically induced viscoelastic properties of MRE. In this review, the influences of several additives on the MR effect of various MR solids including MR elastomers, MR greases, and MR gels, which are recognized as efficient smart materials for practical applications in various engineering fields, are surveyed and discussed.

Role of Additives in Enhancing the Rheological Properties of Magnetorheological Solids: A Review

/pdf/computer-aided-design-manufacturing-modeling-and-simulation-uvku5yzp24.pdf

Computer-Aided Design, Manufacturing, Modeling and Simulation II

This paper investigated the effects of silicone oil viscosity (SOV) and carbonyl iron particle (CIP) weight fraction and size on dynamic yield stress for magnetorheological (MR) grease. The MR grease samples were prepared using orthogonal array L9 on the basis of a new preparation technology. The shear rheological tests were undertaken using a rotational shear rheometer and yield stress was obtained based on the Bingham fluid model. It was found that CIP fractions ranging from 65 wt% to 75 wt% and SOV varying from 50 m2·s-1 to 1000 m2·s-1 significantly affect the magnetic field-dependent yield stress of MR grease, but the CIPs with sizes of 3.2-3.9 μm hardly had any influence based on the analysis of variance (ANOVA). In addition, the yield stress of MR grease mainly depended on the CIP fraction and SOV by comparing their percent contribution (PC). It was further confirmed that there were positive effects of CIP fraction and SOV on yield stress through response surface analysis (RSA). The results showed a high dynamic yield stress. It indicated that MR grease is an intelligent material candidate which can be applied to many different areas requiring high field-induced rheological capabilities without flow for suspension. Moreover, based upon the multivariate regression equation, a constitutive model was developed to express the function of the yield stress as the SOV and fraction of CIPs under the application of magnetic fields.

https://www.mdpi.com/1996-1944/12/11/1778/pdf

Effects of Silicone Oil Viscosity and Carbonyl Iron Particle Weight Fraction and Size on Yield Stress for Magnetorheological Grease Based on a New Preparation Technique

The invention discloses a resistance device based on magneto-rheological cement and a magnetic control rheostat. The resistance device based on the magneto-rheological cement comprises an insulating sleeve, electrodes, magneto-rheological cement and wiring ends, wherein the magneto-rheological cement is fixed inside the insulating sleeve; the electrodes are distributed on the upper inner surface and the lower inner surface of the insulating sleeve, and are in sufficient contact with the magneto-rheological cement; and the wiring ends are welded on the two electrodes. The magnetic control rheostat comprises excitation coils, an upper magnetic pole, a lower magnetic pole and the resistance device based on the magneto-rheological cement, wherein the resistance device based on the magneto-rheological cement is fixed between the upper magnetic pole and the lower magnetic pole; the excitation coils are coiled between the upper magnetic pole and the lower magnetic pole; the excitation coils, the upper magnetic pole, the lower magnetic pole and the resistance device based on the magneto-rheological cement commonly form a closed bidirectional magnetic loop; and the intensity of a magnetic field of the closed magnetic loop is adjusted by controlling the magnitude of the current of the excitation coil, so that the resistance of the resistance device based on the magneto-rheological cement can be changed. The invention designs the rheostat for controlling the resistance value of the device by a magnetic field generated by the current through using the characteristic that the conduction property of the magneto-rheological cement can be enhanced by additionally arranging the magneto-rheological cement with the increase of magnetic fields. The magnetic control rheostat is applicable to an electronic control system or a computer control system.

Resistance device based on magneto-rheological cement and magnetic control rheostat

Magnetorheological (MR) grease is a promising material to replace MR fluid because the advantage in term of stability and less possibility to leaking. To improve the material properties, an accurate model can be critical for reducing the time and cost of the development process. A model has been developed to predict MR fluid material properties by including the composition. However, the model may need adjustment and cannot predict other essential rheology parameters, such as viscosity, apparent viscosity, shear rate, and shear stress. Therefore, the technical novelty of this paper is to propose a model with composition as one of the inputs using extreme learning machine method. A scoring system is also introduced to quantify the significance of the composition effect toward the MR grease performance. Then, the model is simulated and compared with experimental data. The performance shows high accuracy estimation with normalized root mean square error about 1.25%.

A Model of Magnetorheological Grease using Machine Learning Method

Based on computer simulation technology, we put forward the shear stress model of nonspherical magnetic particle MRG, and take the hexagon form magnetic particle MRG as an example; this paper deduces hexagon magnetic particle MRG shear stress formula. The model simulate and calculate the relationship between shear yield stress and magnetic field intensity respectively when radius and side length is equal and when the volume is equal also shear yield stress in the zero field condition. The simulation results show that in the same volume condition the shear yield stress of nonspherical magnetic particle MRG is bigger than that of spherical magnetic particle MRG; the shear yield stress of nonspherical magnetic particle MRG cut down with contacting side length’s reducing but also greater than that of spherical magnetic particle MRG and this relationship is also the same in the zero field condition, so spherical magnetic particle MRG is not the best choice. Therefore, this research has an extremely vital significance for the development and application of high-performance MRG.

Study of Nonspherical Particle Magnetorheological Greases with Computer Simulation Technology

The utility model relates to a magnetorheological fluid electromagnetic characteristic testing device which includes a magnetorheological fluid electromagnetic characteristic converter, a signal preprocessing part, a signal amplifying and filtering part, a data processing part, and a display part. The magnetorheological fluid electromagnetic characteristic converter includes a magnetorheological fluid resistance converter which is composed of a magnetorheological fluid resistor and a resistance-voltage converting circuit, a magnetorheological fluid capacitance converter which is composed of a magnetorheological fluid capacitor and a capacitance-voltage converting circuit, and a magnetorheological fluid inductance converter which is composed of a magnetorheological fluid inductor and a inductance-voltage converting circuit. The magnetorheological fluid resistor and the magnetorheological fluid capacitor take two metal flats as the electrodes, and use an insulating material to package the two electrodes into an enclosed device. The inside of the enclosed device is provided with a magnetorheological fluid. The magnetorheological fluid inductor is an I-shaped inductor, and an I-shaped skeleton is made of the insulating material. The inside of the magnetorheological fluid inductor is filled with the magnetorheological fluid. The skeleton is compactly twisted with a copper coil. The magnetorheological fluid electromagnetic characteristic testing device can display the magnetorheological fluid electromagnetic characteristic parameters and the changing rule in an outer magnetic field real-timely and effectively.

Magnetorheological fluid electromagnetic characteristic testing device

The utility model relates to a magnetorheological fluid intelligent sensing technology and a magnetorheological fluid acceleration intelligent sensing system, and designs a magnetorheological fluid acceleration intelligent sensing system. The utility model is characterized in that: putting a nonmagnetic mass block into a nonmagnetic container filled with magnetorheological fluid; fixing the mass block in the container by using a spring, wherein relative displacement exists between the mass block and the container due to the effect of damping force of elastic force of the spring and the magnetorheological fluid when the container has acceleration; calculating the acceleration of the container by detecting change of the relative displacement; and increasing measurement range of the acceleration by adjusting external magnetic field as the damping factors of the magnetorheological fluid change with the changing external magnetic field. The magnetorheological fluid acceleration intelligent sensing system provided by the utility model has the advantages of high anti external interference capability, high precision, wide measurement range and the like.

Magnetorheological fluid acceleration intelligent sensing system

The invention relates to a magnetorheological fluid acceleration sensor. A non-magnetic mass block is placed inside a non-magnetic container, filled with magnetorheological fluid, and the mass block is fixed in the container by a spring. When the container generates the acceleration, the mass block generates the relative displacement with the container under the effects of the elastic force of the spring and the damping force of the magnetorheological fluid. The acceleration of the container can be calculated through detecting the relative displacement change. Because the damping coefficient of the magnetorheological fluid is changed along with the change of an external magnetic field, the measuring range of the acceleration is regulated through regulating the external magnetic field. The magnetorheological fluid acceleration sensor has the advantages that the measuring range is wide, the precision is high, the sensitivity is high, the response speed is high, and the like.

Magnetorheological fluid acceleration sensor

Magneto-rheological grease attracts the attention as a new kind of intelligent material. Under the external magnetic force, it is difficult to use traditional mathematics model to solve and analysis internal structure because of its complexity and polytropy. The modeling and simulation for complex system using computer becomes a good way to investigate complex system. Based on the electromagnetic theory and computer simulation, this paper constructed the model of shear stress to describe the characteristic of magneto-rheological grease that is to use body centered cubic pillars model to analysis the mechanism and characteristics of magneto-rheological grease. Using matlab simulink toolkit to compose the simulation program, simulate and analysis using theoretic model, and plot the shear stress curve of magneto-rheological grease with magnetic strength and particle size, and the shearing force under zero field. The simulation and experimental results indicate that the simulated shear stress curve is coincidence with experimental curve when the density of ferromagnetic particle is low, and it is lower than experimental curve when the density is high (the variation tendency is close), which verified the accuracy of theoretical model. It needs to improve the model by considering the still friction between ferromagnetic particles.

The Model and Simulation of Magnetorheological Grease Characteristics

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