Rheological Properties Of Magnetorheological Fluid Research Articles

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.

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.

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.

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.

Rheological properties of magnetorheological fluids with different base fluids and a compatible additive

Rheological properties of magnetorheological fluids with different base fluids and a compatible additive

Effect of Oil‐Soluble Graphene on the Tribological and Rheological Properties of Magnetorheological Fluids

Magnetorheological fluid (MRF) is a widely utilized intelligent material that faces the in‐use thickening (IUT) problem caused by wear. As commonly being used polar antiwear agents aggravate the sedimentation of MRF, a new method to improve the tribological properties of MRF using nonpolar oil‐soluble graphene rather than polar additives is proposed. Orthogonal and control experiments conducted with a four‐ball machine show that oil‐soluble graphene greatly improves the antiwear performance of MRF. More specifically, the MRF with oil‐soluble graphene reduces wear volume up to about 90% compared with all control experiments, including blank samples without any additives, the samples with the surfactant but without graphene, and the ones with the commercial antiwear agent ZDDP. The results also indicate that both lubricant and MRF get the best antiwear effect when graphene concentration in the base oil is 2 mg ml−1. This implies that oil‐soluble graphene improves the tribological properties of the systems primarily by enhancing the pressure‐bearing capacity of the carrier fluid. Moreover, oleophilic graphene increases the magnetorheological effect of MRF and reduces its off‐state viscosity by about 4% through isolating particles and filling gaps. In summary, the proposed method can solve the IUT problem of MRF along with ensuring its performance.

A review on rheological properties of magnetorheological fluid for engineering components polishing

Smart materials, by definition, are those materials whose properties change by changing an external factor such as electric current, magnetic field, capacitance etc. One such material is magnetorheological fluid. Magnetorheological fluid is a class of fluid whose apparent viscosity varies over changing magnetic flux density in the range of magnitude 1 T. Without magnetic field, magneto-theological fluid functions as a Newtonian fluid but shifts its essence to that of a non-Newtonian fluid when subjected to a magnetic field. One of the models that depict the behaviour of magnetorheological fluid is Bingham plastic fluid. Similar to Bingham plastic, magnetorheological fluid needs a certain amount of yield stress before it starts to flow, and this certain yield stress relies on the degree of the magnetic flux density applied. Magnetorheological fluids are prepared by dispersing micron-size magnetizable iron particle in a non-magnetizable solution such as deionized water, silicone oils, synthetic hydrocarbons etc. Additives such as greases are often applied to avoid sedimentation and coagulation of material. Through adding the magnetic field, the magnetizable iron particles are tied collectively in chains, along magnetic field lines, and these chain-links thicken the fluid. Conventionally magnetorheological fluids were used in rail locomotive engines, dampers, shock absorber, clutches etc. In the recent decade, magnetorheological fluids are extensively used in the manufacturing industry for finishing purposes. Certain contours, an internal section of pipes etc. are difficult to finish with other methods. Since fluid can flow within internal and hard to reach places, this can be and is manipulated. Magnetorheological fluids mixed with abrasive particles are used for such purposes. This article discusses the preparation, formulation, rheological properties and engineering applications of magnetorheological fluid in details.

Magnetorheological damper modeling based on a refined constitutive model for MR fluids

A systematic modeling study is conducted to predict the dynamic response of magnetorheological (MR) damper based on a refined constitutive model for MR fluids. A particle-level simulation method is first employed to probe the microstructured behavior and rheological properties of MR fluids, based on which the refined constitutive model is developed. The constitutive model is further validated by comparing the predicted results with the data obtained from microscopic simulations and existing experiments. It is revealed that the proposed constitutive model has comparable accuracy and good applicability in representing MR fluids. Subsequently, a computational fluid dynamics (CFD) model is established to explore MR damper’s behavior by using the proposed constitutive model to describe the fluid rheology. For better capturing the dynamic hysteretic behavior of MR damper, a modified parametric model is developed by combing the Bingham plastic model and the proposed constitutive model. The modified model for MR damper shows its validity and superiority over the existing Bingham plastic models.

A novel process of sheet metal inverse bulging pre-deformation for deep drawing forming using magnetorheological fluid as flexible media

At the Magnetic field condition, the surface quality of formed parts can be improved significantly. To investigate the technical advantages of Magnetorheological (MR) fluid as a soft media, eliminate the defects of the parts because of the complex deformation, such as wrinkling, cracking, and over thinning. A new method of sheet deep drawing forming with MR fluid through inverse bulging pre-forming was proposed, which has made the wall thickness distribution more uniform and changed the stress distribution of sheet by changing the rheological property of MR fluid. The theoretical pressure transfer model of MR fluid as media and the configuration model of inverse bulging pre-forming are established. It can be concluded that the relationship between bulge height and load time have been shown consistency compared with experimental results and agree well with the theoretical analysis. And the configuration model have shown good agreement from the experiments results and the numerical results espectively with theoretical results. The uniformity of the wall thickness and the surface quality of the deep-drawn parts are improved significantly with the increase of the inverse bulging height. When the inverse bulging height is about 9 mm, the pre-forming effect is optimal, which provides theoretical guidance and is of much potential to the forming of the and thin-walled complex parts in industry fields.

Effect of base oil lubrication properties on magnetorheological fluids

The effects of the lubricating properties of the base oil on the rheological properties of magnetorheological fluid (MRF) are studied. The results from three base oils with different lubricating performances show that an MRF with poor boundary lubricity has a higher yield stress and is more likely to exhibit shear thickening. The shear stresses and normal force in the MRF and the shear-thickening phenomenon mainly affect by the friction state between the ferromagnetic particles and the plates. The evolution mechanism of the MRF particle structure explain from the perspective of tribology using a normalization method based on the friction coefficient and the Stribeck curve.

Introducing the thermal field into multi-physics coupling for the modeling of MR fluid-based micro-brake

Miniaturization of magnetorheological (MR) fluid-based actuator, as an essential building block of miniature electromechanical systems, is of significant importance. Since the feature size of miniature electromechanical systems 1–10 mm, the heat generation and dissipation process in the MR fluid would dramatically affect the speed reduction mechanism of micro-brake. The objective of this manuscript is to propose a model for the MR fluid-based micro-brake with high accuracy by introducing the thermal field into the multi-physics coupling. The temperature- and field-dependent rheological properties of MR fluid are investigated and the data is presented. The rheological behavior of MR fluid under the comprehensive effect of temperature field, magnetic field and flow field is modeled by introducing the Arrhenius equation. A COMSOL Multiphysics-based simulation method, which includes two heat sources, is proposed to calculate the thermal distribution of the miniature turbine generator under the multi-physics coupling. The influence of temperature on the yield stress τy and the influence of shear rate γ˙ on viscosity η are also introduced into the MR fluid-based micro-brake to obtain a torque calculation model with high precision. The miniature turbine generator was driven with an initial rotational speed of 18,200 r/min. The temperature ranged from 41 to 123 °C as a current from 0.3 to 1.5 A was applied to the micro-brake. Results show that the accuracy has been improved more than 12.9% by introducing thermal analysis to the micro-brake model. We believe this work is significant for realizing the high precision control of MR fluid-based micro-brake at high rotational speeds.

A novel magneto-rheological fluid dual-clutch design for two-speed transmission of electric vehicles

The dual-clutch transmission (DCT) in electric vehicles can significantly decrease the torque interruption and improve the shifting comfort. The magneto-rheological fluid (MRF) is a kind of intelligent material commonly used for torque transmission devices with high control accuracy and fast response, e.g. MRF clutch. This paper proposes a novel MRF dual-clutch (MRFDC) design for the two-speed transmission of EVs combining the DCT and MRF clutch advantages. The MRFDC is composed of an internal clutch and an external clutch. The two clutches with the same input shaft and different output shaft can shift between two gears by controlling the input current through the coils in the two clutches. The relationship between the input current and the magnetic flux density is obtained by the finite element analysis of the magnetic field under different input current. Theoretical analysis is carried out to estimate the output torque of MRFDC according to the geometric dimensions of MRFDC structure and rheological properties of MRF. The Herschel-Bulkley model is applied to describe the MRF behaviour because the shear rate of MRF is relatively high. The output torque model is built considering the magnetic flux density. Therefore, the relationship between the transmissible torque and applied input current is determined. Finally, the MRFDC model is experimentally verified on the testbed; besides, the transmissible torque tests and response time tests for internal and external MRF clutches are carried out, respectively. The test results agree with the simulation results, and the differences are within 2 N m. It is suggested that the MRFDC can be applied in EVs to improve vehicle performance.

Influence of clay-based additive on sedimentation stability of magnetorheological fluid

Sedimentation stability is one of the most important features of magnetorheological (MR) fluids. Clay-based additives are known for improving the stability of the MR fluids. This article describes the dependency of the clay-based additive concentration on the sedimentation stability and the rheological properties of MR fluids in non activated state (without magnetic field). The sedimentation was measured for two different base oil viscosities, two different carbonyl iron particle sizes, and additive concentration between 2 and 6 wt%. The measurements showed that the sedimentation rate exponentially decreases with the additive concentration, while the yield stress is rising. The measurements of rheological properties also showed the dependency of rheological properties of MR fluid with a clay-based additive on loading history. The influence of carrier fluid viscosity or particle size has a minor effect on the sedimentation in comparison with the clay-based additive. The addition of 6 wt% slows down the sedimentation by more than 3000 times compared to MR fluid without additives. The MR fluid with 4.85% of clay-based additive achieves slightly better sedimentation stability than commercial MR fluid LORD MRF122.

Influence of the Drive Plate with Different Surface Textures on the Property of Carbonyl Iron-Based Magnetorheological Fluid

Aiming to study the effect of drive plate with different surface topographies on the wear property of magnetorheological fluid (MRF), some specific experiments are carried out and analyzed in this paper. Firstly, experiment materials and test methods for MRF are elaborated, and four different surface topography drive plates are designed and manufactured. MRF test-bed is built up to test the rheological properties of MRF. Moreover, the surface morphology of particles is taken using a scanning electron microscope (SEM). Finally, experimental results show that there are remarkable influences on tribological properties of carbonyl iron-based MRF with different drive plates. Therefore, the drive plate with specific surface topography can meet the needs of different MRF transmission systems.

Microstructure evolution based particle chain model for shear yield stress of magnetorheological fluids

To predict the shear stress of magnetorheological fluids (MRFs) under magnetic field and shear flows, a meso-microscale shear model is proposed based on the entire course of particle aggregates and chains. For this purpose, a systematic study on the microstructure evolution and rheological properties of MRFs is conducted by using molecular dynamics simulations. An efficient chain identification technique is introduced to count the number of particle chains within the suspension system. From the perspective of particle-level simulations, the microstructured behavior of MRFs involving particle aggregation and internal structure evolution of magnetorheological suspensions are addressed. Shear properties of MRFs derived by the proposed model are studied, and model verification by comparison with previous experimental data and predictions of the existing structural viscosity model is included as well. It is revealed that the proposed meso-microscale shear model exhibits satisfactory accuracy and efficiency for describing the rheological properties of MRFs. Besides, the critical factors linked with rheological properties of MRFs such as magnetic field strength, particle volume fraction and shear rate, are analyzed, further demonstrating the applicability of the proposed model in design and optimization of MRFs.

Shear thickening prevents slip in magnetorheological fluids

Magnetorheological (MR) fluids are smart fluids that solidify upon the application of a magnetic field by virtue of suspended magnetic particles forming chains. Here, the effect of shear thickening additives on the performance of MR fluids is explored and found to increase yield stress by 60% in fluids that have the same iron content. In order to explore the origin of this improvement, a series of flow- and oscillation-based rheology experiments were performed at various plate separations and the results were compared with a discrete dipole model of chain formation and breakage. Ultimately, conventional MR fluids, which are typically shear thinning, are found to yield at small strains that are consistent with slip failure where chains shear apart at one particle-particle joint. In contrast, shear thickening fluids reliably yield at high strain in a manner consistent with affine failure of the chain where each joint is pulled apart equally. The prevention of slip failure is attributed to the shear thickening additive locally increasing the effective viscosity as slip begins, thus preventing it from leading to yield. In addition to motivating the use of shear thickening agents broadly in MR fluids, these findings highlight the importance of additive choice in tuning rheological properties of MR fluids and the benefit of considering the microstructural and bulk behavior of the fluid simultaneously when synthesizing smart fluids.

Influence of Graphite Flakes on the Strength of Magnetorheological Fluids at High Temperature and its Rheology

Magnetorheological fluid (MRF)-based rotating torque transmission devices are gaining popularity such as MR brake and MR clutch. The effectiveness of the developed devices reduces due to thermal thinning behavior such as a decrease in strength at high temperature of MRF. To design MR devices such as MR clutch and MR brakes, it is necessary to maintain the strength of MRF at the higher temperature. Since MRF is the main component of MR devices, the synthesis of good quality MRF is a prime concern. In this research article, the role of graphite flakes on the strength of MRF at high temperature and its rheology is investigated. In this article, the effectiveness of graphite flakes is tested on MRF by selecting different weight fractions. MRF and MRF with graphite flakes (MRFG) have been synthesized with carbonyl iron particles (80 wt%) and graphite flakes (0.5, 1, 2, 3, 4, and 5 wt%). MRF and MRFG are characterized or evaluated by the rheometer. The rheological properties of MRF and MRFG have been examined using rotational tests. Results show the effective use of graphite flakes in MRF. MRFG has a higher value of shear stress than the MRF at high temperature and shear rate.

A new modified model for the rheological properties of magnetorheological fluids based on different magnetic field

Magnetorheological (MR) fluids presents obvious rheological properties under external magnetic fields. A rotational rheometer was adopted to investigate the relationship between shear stress and shear rate of different volume fractions MR fluids under different applied magnetic field strengths, which is one of the most important indicators of rheological property of MR fluids. Shear stress increases with the increasing of applied magnetic field and particles volume concentration. While, MR fluid shows the pseudo-plastic fluid behavior when the volume fraction was 28% without magnetic field. Different constitutive models (i.e. H–B model, S-S model and a modified model used to analyze flowing law of MR fluids) were employed, respectively. Results show that the modified flow model fits well with experimental results as a whole compared to other models, and the modified model is more simple and effective.