Properties Of Magnetorheological Fluids Research Articles

Study on the Effect of Structural Scale of Hollow Particles and Core-Shell Particles on the Properties of Magnetorheological Fluids

Study on the Effect of Structural Scale of Hollow Particles and Core-Shell Particles on the Properties of Magnetorheological Fluids

The Actuating Characteristics of Magnetorheological Fluids Subjected to Particle Sedimentation and Temperature Variation

Magnetorheological (MR) fluids are known for their controllable characteristics under the influence of magnetic fields and, hence, widely used as semi-active actuators for vibration control. Regardless of advantages such as fast response time and reversible property, MR fluids inevitably experience sedimentation caused by significant density mismatches between magnetic particles and carrier liquids. Moreover, the effect of the temperature on actuating characteristics is also one of the problems to be resolved for practical implementation. This study experimentally investigates the sedimentation behavior under various temperatures ranging from 25 to 70 °C using a multiguide-arm magnetic device that generates a uniform magnetic flux density across MR fluids. The sedimentation stability is then observed after 168 h at current inputs of 0, 1, and 2 A, respectively. Subsequently, the field-dependent rheological properties of MR fluids are evaluated using a rheometer and discussed, showing actuating capability, which depends on the viscosity, shear stress, and yield stress before (initial state) and after the sedimentation (sedimentation state). The field-dependent yield stresses, which directly represent the actuating force of the semi-active actuator, are specifically evaluated. Under the on-state condition (2 A) at a temperature of 70 °C, the yield stress decreased from 2.747 kPa (initial state) to 2.352 kPa (sedimentation state). By using this yield stress, the field-dependent damping force was evaluated, showing a decrement from 1672 N (initial state) to 1623 N (sedimentation state) at a velocity of 0.8 m/s. It is shown that the temperature causes the reduction of the actuating properties after the long-term operation. The insightful findings achieved in this work will provide useful information for the evaluation of actuating characteristics of smart MR fluids and the design of MR application systems subjected to particle sedimentation and temperature variation.

Experimental and numerical analysis of magnetorheological valve based on Herschel–Bulkley–Papanastasiou model

As a kind of smart material, magnetorheological (MR) fluids are widely used in various engineering applications. Choosing an appropriate rheological model to describe flow behavior is crucial in the design of MR actuators. In this paper, the Herschel-Bulkley-Papanastasiou (HBP) model was first developed to fit the rheological properties of the MR fluid. The coupling modeling of the flow field and magnetic field of the radial MR valve were established, and the distribution of the magnetic field, velocity field, shear stress, and shear rate of the radial MR valve were also analyzed. The rheological properties of MR fluids and the inlet and outlet pressures of the MR valve were experimental tests. The experimental and numerical results indicate that the HBP model can better fit the rheological characteristics of MR fluids than that of the BP model, and the numerical results can better predict the magnetic field and flow field characteristics of the MR valve.

Study on the tribological and rheological properties of magnetorheological fluids based on different base oils

Abstract Base oil has great influence on the tribological and rheological properties of magnetorheological fluid. In this paper, four types of magnetorheological fluid are prepared respectively by silicone oil, mineral oil, synthetic oil (PAO) and castor oil, and their tribological and rheological properties are investigated. Firstly, the viscosity of the magnetorheological fluid is measured by a viscometer. Then the friction coefficient and wear scar diameter of the magnetorheological fluid is measured by a four ball friction testing machine. Next, the sedimentation rate of the magnetorheological fluids is calculated by the observation method. Finally, the shear yield stress of the magnetorheological fluid is measured by a rheometer. By analyzing the experimental data, it is concluded that the magnetorheological fluid prepared by white mineral oil and castor oil has excellent wear resistance. The magnetorheological fluid prepared by castor oil has better sedimentation stability and higher shear yield stress. Consequently, the magnetorheological fluid prepared by castor oil has better comprehensive properties.

Nanosphere Chain Model of Magnetic Fluid and Its Dynamic Performance.

The magnetorheological effect is a critically important mechanical property of magnetic fluids. Accurately capturing the macroscopic properties of magnetorheological fluids with elongated particle forms, such as nanosphere chains, remains a challenging task, particularly due to the complexities arising from particle asymmetry. Traditional particle dynamics primarily utilize spherical particles as computational units, but this approach can lead to significant inaccuracies, especially when analyzing nonspherical magnetorheological fluids, due to the neglect of particle asymmetry. In this work, an advanced particle dynamics model has been developed by integrating the rotation and collision of these asymmetric particles, specifically tailored for the configuration of nanosphere chains. This model exhibits a significant reduction in error by a factor of 3.883, compared to conventional particle models. The results demonstrate that alterations in the geometric characteristics of magnetic nanosphere chains can cause changes in mesoscopic structures and magnetic potential energy, thereby influencing the mechanical properties at the macroscopic level. This work has developed an accurate mesoscopic simulation method for calculating chain-type magnetorheological fluids, establishing a connection between mesoscopic structures and macroscopic properties, and unveiling the tremendous potential for accelerating the design of next-generation magnetic fluids using this approach.

Tribological and braking performance study of additive-based MR fluids in shear and hybrid mode using MR drum brake

The braking performance of magnetorheological (MR) brake can be improved by utilizing hybrid mode of operation of MR fluid in brake and by enhancing the rheological properties of MR fluid. This work presents an MR drum brake, which can operate in shear mode as well as in shear plus compression mode, i.e., hybrid mode. The use of compression mode increases the interactions of iron particles with the contacting surface of the rotor and stator, which affects the gap of the MR zone, which is one of the performance parameters for MR brakes. Hence, the presented work attempted to prepare an MR fluid that offers not only good tribological properties as well as best braking performance with MR drum brake. So, MR fluids have been prepared using the same percentages of different additives such as graphite flakes, MWCNTs, and zinc oxide. The rheological, tribological, and braking performance of these prepared MR fluids have been studied using a rheometer, tribometer, and brake inertia dynamometer, respectively. The study found that zinc oxide-based MR fluid is the most suitable MR fluid for the presented MR drum brake in terms of braking performance and tribological aspects.

Study of Effect of Graphite Based Magnetorheological Fluids on Braking Performance and Rotor Surface of Magnetorheological Disk Brake Using Full-Scale Brake Inertia Dynamometer

The performance of magnetorheological (MR) brakes depends on the rheological and tribological properties of MR fluid. An additive-free MR fluid does not offer better braking performance, which limits the commercial application of MR brake. In view of these issues, MR fluids were prepared in this present work employing graphite flakes as an additive. The required rheological properties of these MR fluids were measured on the magneto rheometer, and their braking performances were measured as per braking standard IS13453 using a fabricated MR disk brake on a 2/3-wheeler brake inertia dynamometer. Due to the interaction of MR fluid with the rotor and housing surface, the MR gap (i.e., another performance parameter) varies. Therefore, the effect of the interaction of prepared MR fluids on the rotor surface properties of the MR disk brake was also investigated. The constituents of MR fluids generate roughness on the rotor and housing surface. As a result, a mathematical model for surface roughness was presented and verified with experimental results. Based on the study, it is found that 0.5% (w/w) of graphite flake is better than additive-free MR fluid.

Investigation the Effect of MR Fluid Composition on Properties at Low Strain Ranges.

The paper presents the results of eight magnetorheological (MR) fluids of different compositions. Magnetite and carbonyl iron were used as magnetic particles. MR fluids based on glycerin and OKS 352 oil were produced using stabilizers in the form of oleic acid and Aerosil 200 (Evonik Resource Efficiency GmbH, Hanau, Germany) silica; additives such as graphite and yellow dextrin were also used. The aim of the study was to determine the properties of various combinations of components on the dynamic properties of MR fluids, i.e., properties characterizing the fluid within the range of low deformations, as well as to investigate the effect of different compositions on structural yield stress and flow stress prepared MR fluids at different magnetic field induction values.

An experimental study on mechanical properties of a magnetorheological fluid under slow compression

Mechanical properties of magnetorheological (MR) fluids have been investigated in slow compression under different magnetic fields. The compressive stress of the MR fluid has been deduced by assuming that it was a continuous shear flow in Bingham model and has been calculated. The compressive stress has also measured in different magnetic fields and initial gap distances. The compressive stress of the MR fluid in a high magnetic flux density and/or a small initial gap distance was much higher than that predicted by the traditional continuous media theory. Compressive experimental results were also compared with the continuous media theory by a normalized logarithmic form. The achieved experimental result seems to deviate from the prediction by the continuous media theory at a high magnetic flux density and a small initial gap distance. The MR fluid had a high compressive modulus when the compressive strain was lower than 0.042. The compressive modulus had an exponential relationship with the compressive strain higher than 0.042. Frictions between particles, which contribute to the high structure factor, were thought to play an important role in the large deviations in squeeze mode.

The effect of microparticles/nanoparticles surface modification on the magnetorheological fluid properties: A review

Magnetorheological fluids are considered smart materials since their properties change significantly when exposed to a magnetic field, making them interesting for a variety of industries. These fluids are composed of three main components: dispersed particles, carrier fluid, and additives. The latter of which has been the subject of various studies. Therefore, this paper reviews the characteristics and parameters of the particles dispersed in additives and their impact on fluid rheological properties and stability. Also, the surface modification of magnetic and non-magnetic micro and nanoparticles have been investigated. A detailed review of previous studies has been carried out to examine the effects of various parameters such as types of coatings, coating layers, coating thickness, density change, and change in magnetic saturation, on the stability and rheological properties of MR fluids.

On the Application of Support Vector Method for Predicting the Current Response of MR Dampers Control Circuit

Magnetorheological (MR) dampers are controlled energy-dissipating devices utilizing smart fluids. They operate in a fast and valveless manner by taking advantage of the rheological properties of MR fluids. The magnitude of the response of MR fluids, when subjected to magnetic fields, is of sufficient magnitude to employ them in various applications, namely, vibration damping, energy absorption, exoskeletons, etc. At the same time, predicting their response to arbitrary mechanical and electrical inputs is still a research challenge. Due to the non-linearities involved in material properties or the design of the solenoid used for activating the fluid modeling the relationships between the control circuit and the material’s response is complex. Modeling studies can be classified into two categories. The parametric approach requires the knowledge of the internal material’s properties and takes advantage of physics formulas to infer the I/O relationships present in the damper. For comparison, the non-parametric approach harnesses various data mapping techniques to describe the device’s behavior. While the latter is more suited for design studies, the former seems ideal for control algorithm prototyping and the like. In this study, based on the so-called Support Vector Method (SVM), the authors develop a non-parametric model of the control circuit of an exemplary rotary MR damper. To the best of the author’s knowledge, it is the first attempt at an SVM application for MR dampers’ control circuit modeling. Using the acquired experimental data, the I/O relationships are inferred using the SVM algorithm, and its performance is verified across a wide range of excitation frequencies. The obtained results are satisfactory, and the current response of the MR damper is well-predicted. The model performance shows the potential for incorporating it into model-based prototyping and designing of MR control systems.

STUDY OF FACTORS INFLUENCING THE WALL SLIP OF A MAGNETORHEOLOGICAL FLUID

The wall slip of magnetorheological (MR) fluids refers to a phenomenon that affects the application of mechanical properties of magnetorheological fluids due to the relative slippage between the magnetic particles and the transmission wall. In this paper, we analyze and experimentally verify the factors affecting the wall slip of magnetorheological fluids, which can limit the application of magnetorheological-fluid devices. Firstly, from the theoretical point of view, it is considered that the influencing factors are mainly divided into two parts: magnetorheological fluid’s own parameters and transmission surface roughness, among which the parameters include viscosity, mass fraction, etc. When studying the influence of the transmission surface roughness, it is found that different surface morphologies have a great influence on the shear stress. Secondly, a magnetic field simulation analysis and shear yield stress experiments are conducted on shear blocks with different surface morphologies; the obtained results are compared and verified, confirming that different surface shapes affect the shear yield stress by changing the magnetic field distribution of the groove, which in turn changes the wall slip characteristics. These findings provide an effective basis for further research on the wall slip of magnetorheological fluids to improve the transmission effect.

Effect of interfacial shear strength between magnetic particles and carrier liquid on rheological properties of magnetorheological fluids

The interfacial mechanical strength between carbonyl iron particles (CIPs) and carrier liquid is one of the key factors for the rheological properties of magnetorheological (MR) fluids. Here, the microstructure and shear properties of the interface between CIPs and dimethyl silicone oil (DSO) are studied using molecular dynamics simulation. Results indicate that there is strong adhesive strength between Fe atoms on the surface of CIPs and DSO molecular chains during the shearing process. For the MR fluids with DSO viscosity of 50 and 200 mPa⋅s, the DSO molecular structure between CIPs is easy to break out under shear deformation owing to the short DSO chains. While as for the Fe/DSO/Fe model with DSO viscosity of 350 and 500 mPa⋅s, the interfacial shear strength is greatly higher than that with low viscosity DSO due to the entanglement between long chains of DSO. Finally, MR fluids with different viscosity DSO are prepared for rheological tests to verify our simulation results. By combining simulation and experiment, the high interfacial shear strength can improve the rheological properties of the MR fluids. These insights reveal the relationship between the interfacial shear properties of the CIPs/DSO and the rheological properties of MR fluids.

Characterization of Magnetorheological Brake in Shear Mode Using High-Strength MWCNTs and Fumed Silica-Based Magnetorheological Fluids at Low Magnetic Fields

Abstract The performance of magnetorheological (MR) brakes is dependent on the MR characteristics of the braking fluid, working parameters, and magnetic fields. Due to the size limitations, it is quite difficult to use large-sized electromagnet for a high magnetic field inside an MR brake and thus working parameters indirectly affect the MR properties of MR fluid. Again, MR fluids show thermal thinning with working temperature. Therefore, in the present study, MR fluids that have stable MR properties at high temperatures and can provide better braking torque at low magnetic fields are prepared. To improve the MR properties at high temperature, multi-walled carbon nanotubes (MWCNTs) which have high thermal conductivity are used as additives, and initially, three MR fluids are synthesized by varying MWCNT fractions. The MR properties of these fluids are examined and plotted using magnetorheometer. The effective fraction of MWCNTs at which MR fluid has stable MR properties with temperature is identified. It is found that MR fluid which consists of 0.25% fractions of MWCNTs has large yield strength but only at high magnetic fields. To improve its MR properties at a lower magnetic field, 0.5% fraction of fumed silica is mixed with 0.25% fractions of MWCNTs. Then, a fabricated MR disc brake is characterized using those prepared magnetorheological fluids (MRFs). The braking torque of MRFs at different speeds is presented and compared. It is found that approximately 26% more braking torque is offered by fumed silica + MWCNTs-based MR fluid in comparison to other MRFs at 1200 RPM.

Subregional flexible-die control in magnetorheological pressure forming

Magnetorheological pressure forming (MRPF) has shown great flexibility in process control by adjusting the mechanical property of MR fluid. However, the regulation of flexible-die property at present is holistic. In this paper, MRPF based on subregional flexible-die control was proposed, which makes the MR fluid show different force transfer characteristics to meet the requirements of flexible-die performance in different areas. Two kinds of non-uniform magnetic fields were established using the combination of coil and iron core groups based on the measurement and finite element simulations. The MRPF experiments of the Al1060-O sheet using the holistic and subregional flexible-die control methods were conducted. The effects of subregional flexible-die control on loading curve, strain distribution, configuration, wall thickness thinning rate, and fracture characteristics were analyzed. Compared with the case that the specimen ellipticity changes little under the central-dominated magnetic field (CMF), the ellipticity gradually decreases under the fringing-dominated magnetic field (FMF) with the increase of the current. The fracture modes can be divided into three types, and the fracture position transfers from the center of the specimen to the circle of R10mm and then to the die fillet area. The influence mechanism of subregional flexible-die control on sheet deformation behavior and fracture mode is further clarified. The non-uniform distribution of cavity pressure and friction conditions caused by the magnetorheological effect is the main factor affecting the stress states and final deformation behavior of sheet metal. This study provides a new path for intelligent control in sheet metal forming of complex thin-walled parts.

Macro-mechanical properties of magnetorheological fluids based on body-centered cubic structure

This paper addresses the problem that the microstructure model of magnetorheological fluid established by traditional single-chain or multi-chain dense rows is unable to accurately describe the rheological behavior and the sudden change of macroscopic mechanical properties under the action of an applied magnetic field, and analyzes the stable cluster-like structure formed by a specific volume fraction of magnetorheological fluids in a micro-narrow channel under the action of external magnetic field and extrusion pressure. This paper also establishes the equations of motion and dynamics of magnetic particles under the action of external magnetic field, analyzes the dynamic evolution of particle microstructure, performs numerical simulations of two-dimensional chaining using Matlab, and establishes a microscopic observation test bench for comparison and verification; and it establishes a model of complex cluster-like structure of magnetorheological fluids body-centered cubic, and analyzes the system energy, stability and force of the body-centered cubic structure based on the minimum system energy theory and Hertzian contact theory; and further establishes a shear yield stress model based on the body-centered cubic microstructure to analyze the macroscopic mechanical properties of magnetorheological fluids, thereby enriching the theoretical system of extrusion strengthening of magnetorheological fluids in the microscale.

A Novel Dual Helical Magnetorheological Fluid Micro-Robot

To address the problem of flexible drive control of gastrointestinal (GI) tract micro-capsule robot posture, a novel dual helix magnetorheological fluid (MRF) micro-robot (DHMRFMR) is proposed and developed in this paper. Based on the mechanical properties of magnetorheological fluid, the relationship model of magnetic field force is obtained, and the thrust model is established. Double micro DC deceleration motor is used to drive the two ends of the helical actuator to make the DHMRFMR forward and backward, by changing the external magnetic field rotation speed, direction and distance, adjust the attitude direction of the robot. Numerical simulation software ANSYS is used to analyze the motion law of external fluid of DHMRFMR, and the visualization of fluid velocity and pressure distribution is realized. The front-end helix actuator can change the flow path of the fluid, and the middle and tail of the DHMRFMR bear less pressure, which improves the stability and flexibility of the robot. The novel DHMRFMR is suitable for internal drive in bending environment, and has a good application prospect in biomedical engineering field in human intestinal unstructured environment.

Impact of increased particle concentration on magnetorheological fluid properties and their damping performance

Impact of increased particle concentration on magnetorheological fluid properties and their damping performance

Study on mechanism of improving efficiency of permanent-magnet small ball-end magnetorheological polishing by increasing magnetorheological fluid temperature

Permanent-magnet small ball-end magnetorheological polishing method can be used to polish the small part with complex structure. However, the material removal rate of this method is low, which is difficult to improve the output and reduce the cost. In this research, the effect of magnetorheological fluid temperature on the material removal rate is theoretically analyzed by measuring the effect of temperature on the flow properties of magnetorheological fluid, establishing the hydrodynamic model of polishing zone and solving the material removal parameters. It is found that with the increase of the magnetorheological fluid temperature, the polishing relative velocity increases accordingly, which can promote the improvement of material removal rate. But the shear stress decreases accordingly, which inhibits the improvement of material removal rate. The verification experiment results show that the promoting effect can exceeds the inhibitory effect, so that the material removal rate increases with the increase of magnetorheological fluid temperature. When the magnetorheological fluid temperature increases to 60 °C, the material removal rate is improved by 108.4% and the polished surface roughness Sa can reach 14.9 nm. Therefore, increasing the magnetorheological fluid temperature can significantly improve the efficiency of permanent-magnet small ball-end magnetorheological polishing and obtain high quality polished surface.

An overview on properties and applications of magnetorheological fluids: Dampers, batteries, valves and brakes

This paper presents a review of literature that introduces the properties and applications of Magnetorheological fluids(MRFs). first, magnetic particles (iron or cobalt), base fluids(oil (mineral-synthetic) or water), and how to prepare magnetorheological fluids are discussed. Then, in the continuation of this research, considering that magnetorheological fluids are smart and soft liquids, the methods of stability and properties (viscosity, hysteresis loop, Shear yield stress, etc) Of these magnetorheological fluids are discussed. Due to the different properties of Magnetorheological fluids, the behavior of these fluids in different states is discussed. These intelligent fluids change their properties when exposed to an external magnetic field. The most important and obvious feature of magnetorheological fluids is their reversibility from liquid to semi-solid state or vice versa in the Presence or the absence of a magnetic field in a fraction of a second. This change in state and properties is known as the magnetorheological effect. This effect depends on various factors, such as the concentration of magnetic particles, the distribution of magnetic particles, the strength of the magnetic field, additives, and so on. The low magnetic effect and instability of magnetorheological fluids are the most important problems against their widespread use in modern industries. According to research, carbonyl iron particles are the most promising particles for the dispersed phase in MRF. The choice of carbonyl iron particles contributes to their high saturation magnetism, relatively low cost, low coercion, and widespread availability. Finally, according to the different properties and behaviors of these fluids, different applications of magnetorheological fluids are discussed. MRF-based control systems are increasingly used in engineering applications such as rheological magnetic electrolytes in batteries, anti-lock braking systems, magnetic clutches, vibrating dampers, shock absorbers, control valves, and various types of vibrating dampers. One of the newest applications of magnetic fluids is the magneto-rheological electrolyte. The use of MRFs in batteries introduces a new class of magnetic field-sensitive electrolytes that has the potential to increase impact resistance, safety, thermal conductivity, and energy storage in electronic devices through reversible active switching electrolyte mechanical properties.