Magnetorheological Applications Research Articles

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.

A high-speed current source for magnetorheological applications

Current source is an indispensable component of magnetorheological (MR) systems. Though MR fluid has a phase change as fast as in 1 ms, the response of MR damper (MRD) to generate the damping force may be two orders of magnitude longer. Therefore, the rapid response of current source is a key to realize the real-time semi-active control of MR devices. This study proposes a programmable high-speed, low-cost current source exclusively for MR devices based on the synergy between supercapacitor and Buck converter (i.e., SSBC current source). SSBC current source features a strategy consisting of a lifting phase of supercapacitor and a following maintaining phase of Buck converter. Specifically, the high power density of supercapacitor contributes to rapidly lifting/raising the initial current, and then, like a “relay race”, the expected output is maintained through a Buck converter. Theoretical modeling and experiments are performed systematically. The response times (@ 95% of expected outputs) measured are 0.44, 0.84 and 1.88 ms for the outputs of 3, 6 and 9 A, respectively; these values are highlighted as the fastest level in this field. Besides, the response can be up to 24.6 and 43.7 times faster than the cases using supercapacitor and Buck converter to directly drive the MRD, respectively. SSBC current source is employed to generate a sequence of currents/magnetic inductions, only four variables of which need to be controlled programmatically: the order of lifting and maintaining phases, switching time of lifting phase, PWM duty cycle of Buck converter and duration of maintaining phase. The response time stability is verified by 100 cycles of on/off tests, showing a fluctuation of only 1.1%, which indicates a very reliable high-speed response. This study provides an exclusive power supply with a novel strategy for MR devices, which is believed to be an important promotion for MR technologies.

Experimental Investigation on Thermal Stability of Dual Particle Magnetorheological Fluid and Performance

Magnetorheological fluid and their properties are essential in Magnetorheological applications. The present study aims to obtain the thermally stable carrier fluid for Magnetorheological damper application through thermogravimetric analyses of three base fluids for higher stability fluid to synthesize Magnetorheological fluid. Scanning electron microscopic images of particles were also tested for their morphology. Magnetorheological fluid samples with 10%, 15%, and 20% by volume were prepared in-house with a 3% calcium base additive (base fluid). Sedimentation and thermal conductivity studies reveal that increasing particle concentration increases the settling time and thermal conductivity. The flow properties show an increase in yield stress with an increase in particle concentration and magnetic fields. The application part of the fluid consists of Magnetorheological damper fabrication and dynamic testing of 20% volume concentration particles at 10 mm amplitude, 2 Hertz frequency, and 0 Ampere and 0.5 Ampere currents, and the temperature of the system is captured with a K-type thermocouple. The results show an 8.2 °C rise at 0.5 Ampere with a 26.2% force decrease within 1000 cycles. The theoretical model based on the lumped parameter analysis predicts the temperature rise, similar to the experimental analysis with a 9.5% error.

Size effect of iron oxide nanorods with controlled aspect ratio on magneto-responsive behavior

Iron oxide (Fe3O4) has been widely used as a magnetic material for magnetorheological (MR) fluids due to its facile geometric control, magnetic properties, and surface functionalization. However, studies on controlling the aspect ratio of iron oxide nanoparticles applied to MR fluids have rarely been reported due to difficulties in preparing anisotropic magnetic particles. To gain insight into the application of anisotropic nanoparticle in MR fluids, in this work iron oxide nanorods are prepared by using β-FeOOH nanorods as a template. The size of the β-FeOOH nanorods is controlled by adding polyethyleneimine (PEI) as the size controlling agent, and further reduction results in iron oxide nanorods. The resulting iron oxide nanorods are uniform in size and shape and exhibit superparamagnetic properties and high magnetic saturation, which is suitable for MR applications. The influence of particle size of the iron oxide nanorods on MR properties is evaluated, and the result shows the MR fluids prepared with larger size nanorods exhibit higher shear stress due to the higher magnetic saturation ascribed to larger crystalline domain. Consequently, gaining control over the size and aspect ratio of the magnetic particles can lead to high performance MR fluids.

A Review on Vibration Control Strategies Using Magnetorheological Materials Actuators: Application Perspective

Magnetorheological (MR) materials are a group of smart materials used in new technologies with controlled reliability. The development of these materials is expanding, starting from MR fluids, elastomers, grease, and gel. This large number of material types further expands the various applications of MR materials as a creative technology to support performance enhancement. For example, MR fluid is used to improve the performance of shock absorbers such as vehicle suspension, the damping of building structures, and polishing of the workpiece. MR elastomers are used for engine mounting, insulation base, and many other applications with intelligent material properties such as stiffness controllability. However, there are still complexities in the practical implementation of the control system beyond reliability. Many previous studies have focused on the performance improvement and reliability of MR materials as smart materials for application devices and systems. In this review article, the specific discussion related to vibration control strategies in MR material-based systems was thoroughly investigated. To discuss this point, many MR applications including transportation system and vibration isolation were adopted using different types of control strategies. Many different control strategies that have been used for MR applications such as fuzzy logic control, optimal control, and skyhook control are discussed in-depth in terms of the inherent control characteristics of merits and demerits.

Iron Oxide Nanoparticle-Based Ferro-Nanofluids for Advanced Technological Applications.

Iron oxide nanoparticle (ION)-based ferro-nanofluids (FNs) have been used for different technological applications owing to their excellent magneto-rheological properties. A comprehensive overview of the current advancement of FNs based on IONs for various engineering applications is unquestionably necessary. Hence, in this review article, various important advanced technological applications of ION-based FNs concerning different engineering fields are critically summarized. The chemical engineering applications are mainly focused on mass transfer processes. Similarly, the electrical and electronics engineering applications are mainly focused on magnetic field sensors, FN-based temperature sensors and tilt sensors, microelectromechanical systems (MEMS) and on-chip components, actuators, and cooling for electronic devices and photovoltaic thermal systems. On the other hand, environmental engineering applications encompass water and air purification. Moreover, mechanical engineering or magneto-rheological applications include dampers and sealings. This review article provides up-to-date information related to the technological advancements and emerging trends in ION-based FN research concerning various engineering fields, as well as discusses the challenges and future perspectives.

FexCo1-x alloy nanoparticles: Synthesis, structure, magnetic characterization and magnetorheological application

We present results concerning the synthesis of FexCo1-x (0 < x < 1) alloy nanoparticles (NPs) with different compositions by the chemical reduction technique and subsequent structural (XRD patterns), morphological (TEM images) and magnetic (VSM magnetometry) characterization. We have got excellent quality NPs in the cubic bcc structure showing a room temperature magnetization as high as 235 emu/g for the Fe66Co34 composition alloy. Powder of composition Fe47Co53 was used to fabricate a magnetorheological fluid (MRF) by using mineral oil as carrier liquid and Aerosil 300 as additive to control the viscosity of the fluid. This MRF showed a strong magnetorheological response with a superior performance under applied magnetic field up to 616.7 kA/m and good reversibility after demagnetization process. At that highest applied magnetic field, we determined a yield stress value of 2729 Pa, that competes well with the best ones reported in the most recent literature.

Review: A Survey on Configurations and Performance of Flow-Mode MR Valves

Magnetorheological (MR) actuators are semi-active devices controlled by magnetic stimuli. The technology has been commercialized in the automotive industry or high-quality optical finishing applications. It harnesses the rheology of smart fluids to result in the unique application of the material. By a wide margin, the most common example of an MR actuator is a flow-mode single-tube housing with a control valve (electromagnet with a fixed-size air gap filled with the MR fluid) operating in a semi-active vibration control environment. The analysis of the prior art shows that the developed configurations of MR valves vary in size, complexity, the ability to generate adequate levels of pressure, and the interactions with the MR fluid’s rheology resulting in various performance envelopes. Moreover, miscellaneous testing procedures make a direct valve-to-valve comparison difficult. Therefore, in this paper we present a detailed and systematic review of MR control valves, provide classification criteria, highlight the operating principle, and then attempt to categorize the valves into groups sharing similarities in the design and performance envelope(s). Moreover, a simple performance metric based on the shear stress calculation is proposed, too, for evaluating the performance of particular valving prototypes. In the review, we discuss the key configurations, highlight their strengths and weaknesses and explore various opportunities for tuning their performance range. The review provides complementary information for the engineers and researchers with a keen interest in MR applications, in general. It is an organized and and critical study targeted at improvements in the categorization and description of MR devices.

Applications of Magnetorheological Fluid Actuator to Multi-DOF Systems: State-of-the-Art from 2015 to 2021

This review article presents various multi-DOF application systems that utilize smart magnetorheological (MR) fluid. It is well known that MR fluid has been actively studied and applied in many practical systems such as vehicle suspension dampers. The design requirements for the effective applications of MR fluid include geometry optimization, working principles, and control schemes. The geometry optimization is mostly related to the size minimization with high damping force, while the working principles are classified into the shear mode, the flow mode, and the squeeze mode depending on the dominant dynamic motion of the application system. The control schemes are crucial to achieve final targets such as robust vibration control against disturbances. It should be addressed that advanced output performances of MR application systems heavily depends on these three requirements. This review article presents numerous application systems such as sandwich structures, dampers, mounts, brakes, and clutches, which have been developed considering the three design requirements. In addition, in this article some merits and demerits of each application system are discussed to enable potential researchers to develop more effective and practical MR application systems featuring the multi-DOF dynamic motions.

A new magnetic core model for magnetorheological fluid-based applications considering fringing effect of gap and magnetic nonlinearity of fluids

This research aims to introduce a new magnetic core model for magnetorheological (MR) applications requiring high and wide controllable force. In general, the existing models linearize the magnetic behavior of magnetic cores for computational convenience. However, when MR applications such as MR damper require both high actuating force and relatively wide controllable force range, the nonlinearity of the magnetic properties becomes significant, which makes a big difference between the model and actual result. For this reason, the finite element method (FEM) is frequently adopted for modeling the magnetic cores, but it requires a lot of cost and time. To compensate for these disadvantages, a new nonlinear magnetic core model considering both the nonlinearity of the B–H curve of MR fluid and the fringing effect of the gap is proposed in this work. The approach is an extension of Kirchhoff’s law, which performs conformal mapping and backward calculation techniques. After formulating the analytical model, a magnetic core with specific parameters is designed as an illustrative example to validate the proposed model. It is shown through comparative investigations on the proposed model, linearization model, and FEM model that the proposed model is very effective to predict the high controllable force of MR applications.

Anisotropic magnetorheological elastomers with carbonyl iron particles in natural rubber and acrylonitrile butadiene rubber: A comparative study

This work examines magneto-rheological elastomers (MREs) based on isotropic and anisotropic distribution of carbonyl iron particles (CIP) in natural rubber (NR) and acrylonitrile butadiene rubber (NBR). Measurements of the compressive mechanical properties were done to determine the isotropic and anisotropic properties of the MREs. Scanning electron microscopy (SEM) and optical microscopy were employed to study the CIP filler mixing behavior in the rubber matrix and orientation of particles in an anisotropic state. CIP-NBR composites show higher ultimate compressive stress in both isotropic and anisotropic states than NR-based composites. NBR-based composites show positive increases in both the elastic modulus and compressive stress at higher deformation when changing from isotropic to anisotropic, whereas NR-based composites show a positive increase in the elastic modulus and a decrease in the compressive stress. Elastic modulus measurements of anisotropic composites under a magnetic field suggest that NBR composites have much better field-dependent magnetic properties than NR composites. Anti-stress-relaxation measurements indicate that NBR composites have better magnetic effect than NR composites. The better performance of NBR-based anisotropic composites in field-dependent and independent behaviors might be due to better filler distribution, a greater number of chain-like filler structures, and less aggregation of the chain-like filler strands. The MREs based on NBR could be more useful than NR for wide range of magneto rheological applications.

Nanoparticles Functionalized by Conducting Polymers and Their Electrorheological and Magnetorheological Applications.

Conducting polymer-coated nanoparticles used in electrorheological (ER) and magnetorheological (MR) fluids are reviewed along with their fabrication methods, morphologies, thermal properties, sedimentation stabilities, dielectric properties, and ER and MR characteristics under applied electric or magnetic fields. After functionalization of the conducting polymers, the nanoparticles exhibited properties suitable for use as ER materials, and materials in which magnetic particles are used as a core could also be applied as MR materials. The conducting polymers covered in this study included polyaniline and its derivatives, poly(3,4-ethylenedioxythiophene), poly(3-octylthiophene), polypyrrole, and poly(diphenylamine). The modified nanoparticles included polystyrene, poly(methyl methacrylate), silica, titanium dioxide, maghemite, magnetite, and nanoclay. This article reviews many core-shell structured conducting polymer-coated nanoparticles used in ER and MR fluids and is expected to contribute to the understanding and development of ER and MR materials.

Material Characterization of Hardening Soft Sponge Featuring MR Fluid and Application of 6-DOF MR Haptic Master for Robot-Assisted Surgery.

In this work, the material characterization of hardening magneto-rheological (MR) sponge is analyzed and a robot-assisted surgery system integrated with a 6-degrees-of-freedom (DOF) haptic master and slave root is constructed. As a first step, the viscoelastic property of MR sponge is experimentally analyzed. Based on the viscoelastic property and controllability, a MR sponge which can mimic the several reaction force characteristics of human-like organs is devised and manufactured. Secondly, a slave robot corresponding to the degree of the haptic master is manufactured and integrated with the master. In order to manipulate the robot motion by the master, the kinematic analysis of the master and slave robots is performed. Subsequently, a simple robot cutting surgery system which is manipulated by the haptic master and MR sponge is established. It is then demonstrated from this system that using both MR devices can provide more accurate cutting surgery than the case using the haptic master only.

Effect of solvents on the structure and magnetic properties of pyrolysis derived carbon globules embedded with iron/iron carbide nanoparticles and their applications in magnetorheological fluids

Carbon globules embedded with magnetic iron/iron carbide nanoparticles were synthesized by pyrolysis route using different organic solvents (benzene/toluene/xylene) along with ferrocene as iron catalyst precursor. All other synthesis parameters were kept constant (e.g. reaction temperature ≈ 950 ºC, heating rate of 3 ºC/min). We observed a variation of magnetic phase composition with the type of solvent (carbon source) used for synthesis, although the morphology of all the samples was similar. Improved sample crystallinity, distribution of particles and saturation magnetization were obtained, when toluene was used as solvent. Interestingly, rod shaped magnetic particles were observed in case of benzene, whereas for toluene and xylene, all iron-based magnetic particles were spherical. Due to higher saturation magnetization, we have used the particles prepared using toluene as a solvent to demonstrate the magnetorheological behaviour of these carbon-coated magnetic nanoparticles. We observed good magneto-response for the samples suggesting that these particles are potential candidate for magnetorheological applications.

Magnetic field angle dependent hysteresis of a magnetorheological suspension

Magnetorheological (MR) materials are of growing interest for a development and realisation of adaptive components and damping devices. The influence of the magnetic field orientation on the rheological properties of smart materials like MR fluids or magnetic hybrid composites is a key aspect which still is not fully understood, but occurs in almost every real life MR application. To cope with the practical needs and efficiently utilise these smart materials while taking into account their material phenomena experimentally validated practice-oriented models are needed. The authors use a coupled phenomenological approach to adjust and discuss a developed theoretical model based on experimentally obtained data. In addition the data helps to get a better understanding of internal processes and interrelations in MR suspensions.

Design and Evaluation of a Semi-Active Magneto-rheological Mount for a Wheel Loader Cabin

In this study, a semi-active magneto-rheological (MR) mount is designed and manufactured to minimize unwanted vibrations for the cabin of heavy vehicles. Normally, working conditions in heavy vehicles are extremely rugged. Usually, the heavy vehicles use passive rubber mounts for the reduction of vibrations from road. However, the passive mount has definite performance limitations because the passive mount has a fixed resonance frequency when the design is finished. An MR application is one of the solutions because the viscosity of MR fluid can be controlled. As a first step, an experimental apparatus was established for performance evaluation of the mounts. The apparatus has hydraulic excitatory, force, and displacement sensors. Performance of two different passive mounts used in industrial fields were evaluated. The passive mount data of force-displacement, force-velocity, and displacement transmissibility were collected and tested. After that, an MR mount was designed and manufactured that provides better performance using the passive mount data. The MR mount uses two different flow paths, annular duct and radial channels, for generating the required damping force. The field-dependent damping forces were then evaluated with respect to the moving stroke and input current. In this work, in order to control the damping force, an on-off controller associated with the fast Fourier transform (FFT) was used. The control results of the MR mount were compared with the results of passive rubber mounts. It was shown that the semi-active MR mount can attenuate vibrations more effectively at all frequency ranges compared with the passive rubber mount.

Graphene/graphene oxide: A new material for electrorheological and magnetorheological applications

The presence of functional groups provides graphene oxide sheets amphiphilic abilities with lower electrical conductivity and relatively high polarizability, which is appropriate for its electrorheological effect. In addition, because the graphene oxide sheets possess high surface area and relatively low particle density, graphene-/graphene oxide–supported materials have also attracted significant interest for fascinating magnetorheological applications. In this article, we briefly review the fabrication mechanisms and electrorheological characteristics of graphene-/graphene oxide–based electrorheological systems, such as pure graphene oxide sheets and various graphene-/graphene oxide–based polymer composites and nanocomposites of graphene/graphene oxide sheets with inorganic particles. As for the magnetorheological fluid application, the fabrication of graphene oxide sheets coated on the surface of carbonyl iron particles and graphene oxide/iron oxide composites are covered regarding improved dispersibility of the magnetorheological suspensions.

Rheological properties of soft magnetic flake shaped iron particle based magnetorheological fluid in dynamic mode

In this work, the effect of particle shape (flakes) on the magnetorheological (MR) properties of an iron based MR fluid, constituted of two different volume fractions of particles dispersed in a liquid carrier, is studied. To compare the MR effect, spherical iron carbonyl particle based MR fluid is studied. In both MR fluids, linear viscoelastic behavior has been extensively investigated using small amplitude oscillatory analysis and magnetic sweep tests, in the presence and absence of a magnetic field (H). The amplitude sweep tests reveal that flake-based MR fluid shows a higher storage modulus compared to sphere-based MR fluid and saturates at a lower magnetic field strength. The variation of storage modulus with magnetic field strength shows an Hn dependence, where n varies from 2.2 to 2.4 for 20% volume fraction while it varies from 1.6 to 2 for a dilute sample. In the case of sphere-based MR fluid, at 20% volume fraction the variation of storage modulus is nearly linear with the magnetic field at low strain amplitude, and with increasing strain amplitude shows H2 dependence. At lower volume fraction in both cases, the loss modulus increases linearly with the magnetic field strength. The observed enhancement in the MR effect in the flake-based MR fluid is likely due to the stronger particle–particle interaction which results in higher friction between the particles. The sedimentation rate decreases by nearly 50% when flakes are used. The study reveals that one can use the irregular shaped particles for MR applications at low fields (∼80 kA m−1).

Nanostructured Magnetic Particles with Polystyrene and Their Magnetorheological Applications

Magnetorheological (MR) fluids are known to be colloidal suspensions of magnetic particles in a non-magnetic fluid, and exposure to a magnetic field transforms the fluid into a plastic-like solid in milliseconds. To improve the stability against sedimentation and uniform dispersion, two different MR candidates, soft magnetic carbonyl iron (CI) microspheres and magnetite (Fe3O4) particles were modified with polystyrene to be applied for MR fluids in this study. After modification, their unique morphology, crystalline structure and magnetic properties were examined in addition to MR performance and sedimentation characteristics. It was found that this embedded morphology not only effectively prevents direct contact of the magnetic species thus improving particle dispersion but also leads to obvious change in their density, compared with the traditional polymer coating method with a core-shell structure.

Two-layer coating with polymer and carbon nanotube on magnetic carbonyl iron particle and its magnetorheology

Magnetic carbonyl iron (CI)-based magnetorheological (MR) fluids generally posses serious dispersion defects due to the large density mismatch between the CI particles and continuous oil medium, which restricts further MR applications. Polymer coating technology has been introduced in an attempt to reduce the density or prevent CI particle aggregation. In this study, a unique functional coating composed of a polyaniline layer and multiwalled carbon nanotube nest was fabricated on the surface of CI particles using a dispersion polymerization and solvent casting method to improve the sedimentation problem of CI-based MR fluids when dispersed in medium oil. The coating morphology was analyzed by scanning electron microscopy. The effect of the functional coating on the MR performance along with the sedimentation observations was investigated using a rotational rheometer. The results showed that the sedimentation of dispersed particles was improved considerably by the reduced density and rough morphology.