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This study investigated the effect of magnetic particle size and volume fraction on the shear yield stress and dynamic viscosity of magnetorheological fluids. Magnetorheological fluids with varying volume fractions of micro‐ and nanoscale magnetic particles were prepared. A plate‐on‐plate shear test bench was constructed to evaluate the fluids under a constant shear rate, with the applied current ranging from 0 A to 1.2 A. Results indicated that the shear yield stress initially increased and then decreased as the volume fraction of magnetic nanoparticles increased, reaching a maximum of 47 kPa at a volume fraction of 7 %. However, the excessive addition of magnetic particles or large‐diameter particles led to settling and reduced stability of the fluids. The findings suggest that optimizing the size and volume fraction of magnetic particles is crucial for maximizing the shear yield stress of magnetorheological fluids. [ABSTRACT FROM AUTHOR]

Magnetorheological fluids (MRFs) are functional fluids that exhibit rapid and reproducible rheological responses to external magnetic fields. An MRF has been utilized to develop a haptic device with precise haptic feedback for teleoperative surgical systems. To achieve this, we developed several types of compact MRF clutches for haptics (H-MRCs) and integrated them into a twin-driven MRF actuator (TD-MRA). The first TD-MRA prototype was successfully used to generate fine haptic feedback for operators. However, undesirable torque ripples were observed due to shaft misalignment and the low rigidity of the structure. Additionally, the detailed torque control performance was not evaluated from both static and dynamic current inputs. The objective of this study is to develop a second prototype to reduce torque ripple by improving the structure and evaluating its static and dynamic torque performance. Torque performance was measured using both constant and stepwise current inputs. The coefficient of variance of the torque was successfully reduced by half due to the structural redesign. Although the time constants of the H-MRC were less than 10 ms, those of the TD-MRA were less than 20 ms under all conditions. To address the slower downward output response, we implemented an improved input method, which successfully halved the response time. [ABSTRACT FROM AUTHOR]

In this study, we conducted an aeroelastic stability analysis of a laminated composite magnetorheological fluid (MRF) sandwich panel in supersonic airflow for varying yawed angles. The aeroelastic equations for a rectangular sandwich panel (MRF core layer and composite cross‐ply laminate constraining and host layers) were established using a MIN3 plate element. Aerodynamic forces for different yawed angles would result in different coupled flutter boundaries of the panel. The first‐order piston theory with a flow‐yawed angle was employed. The flutter dynamic pressure was obtained through eigenvalue analysis. The effects of various parameters such as the magnetic field intensity, MRF core and constraining layer thicknesses, ply orientation, and yawed flow angle on the flutter dynamic pressure were studied for the simple‐ and fixed‐support boundary conditions. Our results demonstrated that the flutter dynamic pressure of the laminated composite MRF sandwich panel (i) increased for increasing magnetic field intensity and constraining layer thickness; (ii) initially decreased and then increased with the increasing MRF core thickness; and (iii) was strongly influenced by the ply orientation and yawed flow angle. [ABSTRACT FROM AUTHOR]

The coating effect of 1,2-bis(triethoxysilyl)ethane (BTES) on carbonyl iron particles (CIPs) was enhanced by etching with hydrochloric acid (HCl) of various concentrations, and magnetorheological fluids (MRFs) with significantly improved dispersion stability were obtained. The microstructures, coating effect, and magnetism of CIPs were examined using scanning electron microscopy (SEM), automatic surface and porosity analysis (BTE), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and a vibrating sample magnetometer (VSM), respectively. Furthermore, the rheological properties and dispersion stability of the MRFs were assessed by a rotating rheometer and a Turbiscan Tower. The results show that as the HCl concentration increased, nanopores appeared on CIPs and then disappeared, and the specific surface area of the particles increased and then decreased. When the concentration of HCl was 0.50 mol/L, the number of nanopores and the specific surface area of particles changed sharply. Not only that, the coated mass of BTES increased greatly and the saturation magnetization of particles decreased sharply. As the coated mass increased, without a magnetic field, the viscosity and shear stress of the MRFs increased, especially when the coated mass was more than 2.45 wt.%; while under a magnetic field, the viscosity and shear stress decreased, and the sedimentation rate of the MRFs decreased from 0.13 to 0.01 mm/h. By controlling the concentration of HCl for etching, the coating effect of CIPs was greatly enhanced, and thus an MRF with superior shear stress and excellent dispersion stability was obtained, which is significant in basic research and MRF-related applications. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The coupling analysis of the magnetic field and temperature field of a multi-drum dual-coil magnetorheological (MR) brake is presented in this article. Firstly, the structure of the multi-drum dual-coil MR brake is introduced, and a prototype is manufactured. Thermal analysis of the designed brake is carried out, and a torque correction factor is proposed in order to reduce the error between simulation and experimental results. Then, a coupling analysis model of the magnetic field and temperature is established to study the temperature analysis of the brake under steady-state and transient condition. Simulation results show that the allowable slip power in steady state is 23.68 W. The highest temperature occurs in the fluid gap, and the lowest temperature occurs at the shaft. Under the transient state, the brake can work for about 1200 s under 75.08 W slip power. Furthermore, the temperature characteristics of MR brake under the normal braking, emergency braking, and intermittent braking have been studied. An experimental platform is built to study the torque and temperature characteristics. Results show that the simulated temperature is in good agreement with the experiments, indicating that the proposed magnetic-temperature coupling model can accurately simulate the temperature characteristics of the MR brake. [ABSTRACT FROM AUTHOR]

AbstractThe objective of the present work is to improve the speed and vibration characteristics of tracked vehicles via a semi-active suspension system that uses a Magneto-Rheological (MR) damper. MR damper is designed, manufactured, and tested with different harmonic excitations. The MR damper reliability under high-frequency stresses is considered in the mechanical design phase as well as the configurations and dimensions of the damper. Two fluid samples DELTA and GAMA are prepared, which differ in carrier fluid dynamic viscosities to have different rheological properties and tested to determine the dynamic characteristics of the damper. The damper’s ability to isolate vibration is measured by MTS. The investigation performed not only clarifies MR fluid characteristics but also proves the fact that the fluid is non-Newtonian with good rheological properties. One of the two fluid samples called DELTA is found to have the required properties. The MR damper filled with this DELTA shows a significant increase in damping force according to the excitation current and is much higher than the conventional passive suspension damping force. The proposed damper can cope with the increase in both magnitude and frequency of the input, which represents the speed of the truck and roughness of the road. Upgrading the suspension system of the vehicle from a passive damper to a manufactured semi-active MR damper with MR fluid DELTA can increase the damping force that the passive damper produces by 207% in compression stroke and 136.2% in rebound stroke at the same testing conditions. [ABSTRACT FROM AUTHOR]

A methodology for design of magnetorheological dampers for damping vibration of overhead power lines with voltages above 110 kV is proposed, which includes a finite element model of the behavior of the working magnetorheological fluid in a hydraulic channel, and a Matlab model of dynamic processes in a loaded damper. This technique uses tables of damping coefficient values instead of the hysteretic displacement variable characteristic of the Bouc–Wen model, i.e., they use variables and parameters with a physical meaning, known at the stage of formulating technical requirements or determined by calculations. To verify and evaluate the accuracy of the technique, a vibration model of a section of AC 150/19 wire is studied as a system with lumped parameters, suspended on garlands of intermediate support insulators using magnetorheological dampers. [ABSTRACT FROM AUTHOR]

This study proposes two adaptive controllers and applies them to the vibration control of an in-wheel motor vehicle's (electric vehicle) suspension system, in which a semi-active magnetorheological (MR) damper is installed as an actuator. As a suspension model, a nonlinear quarter car is used, providing greater practical feasibility than linear models. In the synthesis of the controller design, the values of the sprung mass, damping coefficient and suspension stiffness are treated as bounded uncertainties. To take into account the uncertainties, both direct and indirect adaptive sliding mode controllers are designed, in which the principal control parameters for the adaptation law are updated using the auto-tune method. To reflect the practical implementation of the proposed controller, only two accelerometers are used, and the rest of the state values are estimated using a Kalman observer. The designed controller is applied to a quarter car suspension model of an in-wheel motor vehicle featuring an MR damper, followed by a performance evaluation considering factors such as ride comfort and road holding. It is demonstrated in this comparative work that the proposed adaptive controllers show superior control performance to the conventional proportional–integral–derivative (PID) controller by reducing the vibration magnitude by 50% and 70% for the first and second modes, respectively. In addition, it is identified that the second mode (wheel mode) of the in-wheel motor vehicle is more sensitive than the first body mode depending on the mass ratio between the sprung and unsprung mass. [ABSTRACT FROM AUTHOR]

This article aims to study the physical characterization and performance of a material‐based magnetorheological fluid (MRF) dampers for vibration attenuation of a high‐speed rotor–motor system near resonance. Four samples are synthesized by combining electrolytic iron and carbonyl iron (CI) with Castor and Karanja oil and experimentally investigated for their contribution to vibration attenuation. The results demonstrate effective vibration attenuation of the biodegradable oil‐based MRF damper than the nonbiodegradable oil‐based MRF damper. The best vibration attenuation is observed in the case of moderately viscous MRF. CI‐based samples exhibit a lower sedimentation rate, hence recommended for MRF. The vibration amplitude is maximum for the Castor oil‐based MRF damper, however, is minimum for the Karanja oil‐based MRF damper. The steady and transient results of vibration amplitudes are obtained and analyzed for different currents supplied to the MRF damper. The range of unstable speed near resonance is also obtained. The prepared samples show higher attenuation of 6–25% than Sample 5. The vibration amplitude attenuation of Sample 4 and Sample 5 are 47% and 22%, respectively. The findings of this study carry significant implications for controlling the vibration of the dynamic system using an eco‐friendly damping system. [ABSTRACT FROM AUTHOR]

Stability and vibration control are major challenges for applications in which laminated composite beams are being used. Using composite base materials with higher strength and/or using appropriate layout orientation are the two potential methods to improve the dynamic performance of laminated composite structures. However, using composite materials with higher strength significantly increases the manufacturing cost. Recently, layers/segments of Magnetorheological (MR) fluids have been added to the common laminated beams, the so-called MR-laminated beam, to improve the dynamic characteristics of such structures. The present work investigates the effect of base materials and applied magnetic field on the dynamic response of MR-laminated beams. Different composite materials, including E-glass, carbon fiber, and Kevlar, have been used as base materials to build the sandwich MR-laminated beam. The hollow spaces of the sandwich beam are filled with MR fluid to fabricate a testing sample for experimental purposes. A modified layerwise theory, N-layer, has been used to determine the vibration response of the structures. It is concluded that applying a magnetic field increases the natural frequency of the MR-laminated beam. In fact, applying 1400-Gauss magnetic fields to a low-cost material like E-glass provides the same natural frequency as that of the fiber-carbon without magnetic fields. [ABSTRACT FROM AUTHOR]

In an effort to enhance the research efficiency of magnetorheological fluid (MRF) sedimentation stability and to improve the current reliance on experimental measurement for assessing sedimentation performance, this paper employs a kinetic approach to simulate a microscale mechanical model for magnetic particles. We propose a simulation method for MRF sedimentation under zero magnetic field conditions and validate it through inductance-based sedimentation detection experiments. Since MRF sedimentation occurs in the absence of a magnetic field, we extend the microscale mechanical model, originally developed under the influence of a magnetic field, by introducing the effects of Brownian and van der Waals forces. The simulation method is parameterized with MRF-specific values and compared against experimental data obtained through inductance-based sedimentation detection. The results demonstrate that the introduced simulation method, incorporating Brownian and van der Waals forces, accurately predicts MRF sedimentation rates, effectively addressing the time-consuming nature of current investigations into MRF sedimentation stability. [ABSTRACT FROM AUTHOR]

A magnetorheological self-centering brace (MR–SCB) has been proposed to improve the energy dissipation capability of the brace. In this paper, a 15-story MR–SCB braced frame is numerically analyzed to examine its seismic performance and resilience. The MR–SCB provides higher lateral stiffness than the buckling restrained brace and greater energy dissipation capability than the existing self-centering brace. The brace also exhibits a reliable recentering capacity. Under rare earthquakes, the maximum average residual deformation ratio of the structure is less than the 0.5% limit. Under mega earthquakes, the maximum average interstory drift ratio of the structure does not exceed the 2.0% elastoplastic limit, and its maximum average floor acceleration ratio is 1.57. The effects of mainshock and aftershock on the structural behavior are also investigated. The interstory drift and residual deformation of the structure increase with the increase of the intensity of the aftershock. Under aftershocks with the same intensity as the mainshocks, the maximum increment of the residual deformation ratio of the structure is 81.8%, and the average interstory drift ratios of the 12th, 7th, and 3rd stories of the structure are increased by 13.4%, 9.2% and 7.5%, respectively. The strong aftershock may significantly cause increased damage to the structure, and increase its collapse risk and residual deformation.

Abstract The dispersion stability of carbonyl iron particle (CIP)-based magnetorheological fluid (MRF) is improved by CIP, which particle is etched with hydrochloric acid (HCl) to form porous structure with many hydroxyl groups and subsequently coated with silane coupling agents that have varying chain lengths. The microstructures, coating effect and magnetism of the CIPs were examined using the Scanning Electron Microscopy, Automatic Surface and Porosity Analyzer (BET), Fourier-Transform Infrared Spectroscopy, Thermogravimetric Analysis and Vibrating Sample Magnetometer. Furthermore, the rheological properties and dispersion stability of the MRFs were assessed using a Rotating Rheometer and Turbiscan-lab. The results revealed that the nanoporous structure appeared on the CIPs and the specific surface area increased remarkably after being etched by hydrochloric acid. Additionally, as the chain length of the silane coupling agent increases, the coated mass on the particles increases, the the density and the saturation magnetization of particles decreased, and the coated particles with different shell thicknesses were obtained; without a magnetic field, the viscosity of MRF prepared by coated particles increase slightly, due to the enhancement of special three-dimensional network structure; under a magnetic field, the viscosity of the MRF decreased distinctly; the sedimentation rate of MRF decreased from 58 to 3.5% after 100 days of sedimentation, and the migration distances of the MRFs were 22.4, 3.7, 2.4, and 0 mm, with particle sedimentation rates of 0.149, 0.019, 0.017, and 0 mm/h, respectively. The MRF with high dispersion stability was obtained, and the etching of CIP by HCl and the proper chain length of the coating of silane coupling agent were proved effective manners to improve the dispersion stability of MRF.

The dispersion stability of carbonyl iron particle (CIP)-based magnetorheological fluid (MRF) is improved by CIP, which particle is etched with hydrochloric acid (HCl) to form porous structure with many hydroxyl groups and subsequently coated with silane coupling agents that have varying chain lengths. The microstructures, coating effect and magnetism of the CIPs were examined using the Scanning Electron Microscopy, Automatic Surface and Porosity Analyzer (BET), Fourier-Transform Infrared Spectroscopy, Thermogravimetric Analysis and Vibrating Sample Magnetometer. Furthermore, the rheological properties and dispersion stability of the MRFs were assessed using a Rotating Rheometer and Turbiscan-lab. The results revealed that the nanoporous structure appeared on the CIPs and the specific surface area increased remarkably after being etched by hydrochloric acid. Additionally, as the chain length of the silane coupling agent increases, the coated mass on the particles increases, the the density and the saturation magnetization of particles decreased, and the coated particles with different shell thicknesses were obtained; without a magnetic field, the viscosity of MRF prepared by coated particles increase slightly, due to the enhancement of special three-dimensional network structure; under a magnetic field, the viscosity of the MRF decreased distinctly; the sedimentation rate of MRF decreased from 58 to 3.5% after 100 days of sedimentation, and the migration distances of the MRFs were 22.4, 3.7, 2.4, and 0 mm, with particle sedimentation rates of 0.149, 0.019, 0.017, and 0 mm/h, respectively. The MRF with high dispersion stability was obtained, and the etching of CIP by HCl and the proper chain length of the coating of silane coupling agent were proved effective manners to improve the dispersion stability of MRF. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to overcome the traditional thin-walled tubes' shortcomings of fixed crashworthiness and poor environmental adaptability, a magnetorheological bionic energy-absorbing element (MBEE) inspired by the horsetail structure was proposed and applied to design of thin-walled tubes in achieving variable and controllable crashworthiness. Theoretical analysis, numerical analysis, and optimization were conducted to perform in-depth study toward improving crashworthiness and associated controllability of the MBEE. In theoretical analysis, the theoretical models of total energy-absorption and crashworthiness' controllability were developed. In numerical analysis, a compression of MBEE under a constant loading speed was simulated using a finite element (FE) software and simulation results showed that: (1). differences on the total energy-absorption of magnetorheological fluid and structural framework in the compression of the MBEE predicted by FE simulation and theoretical model were only 3.49% and 2.16%, respectively. (2). the controllability of the MBEE's crashworthiness was up to 27.73% at the beginning of compression, but decreased to 12.29% when the total length of MBEE was compressed by nearly 67%. (3). the controllability of the MBEE's crashworthiness predicted by theoretical model and simulation also had high consistency. Finally, the parametric study and optimization were conducted to obtain the MBEE with optimal cross-sectional geometric shape filled into the traditional 9-cell thin-walled tube. When compared with the traditional 9-cell thin-walled tube, the total energy-absorption of the tube filled by the optimal MBEE was increased by 251.16%, and the specific energy absorption ( SEA ) of its structural framework was increased by 58.66%. In addition, the initial controllability η int of this filled tube's crashworthiness was up 22.24%. [ABSTRACT FROM AUTHOR]

Damping involves the various frictional and other obstructive effects that attenuate free vibration. For a long time, people have mainly used it to make various dampers to reduce mechanical vibration and consume kinetic energy. It is widely used in fields such as aerospace, automotive, and consumer electronics. These dampers mainly act on mechanical structures. In recent years, with the rapid development of novel human–machine interaction methods and force/tactile feedback technology, the damper has begun to act on people, such as when a person interacts with a robot and their force is applied to a structure with damping. This type of damper requires variable damping, and the amount of variation is controlled by the magnitude of human action. This study used magnetorheological fluid (MRF) instead of traditional damping fluids, such as silicone oil, sesame oil, and mechanical oil. Magnetorheological fluid is a controllable fluid with magnetorheological effects, and its viscosity (hardness) can be changed by changing the nearby magnetic field. This study took the design of variable damping keyboard buttons with haptic feedback as an example to study the electromagnetic and dynamic models of variable dampers based on magnetorheological fluids. The experimental setup was designed and used to verify the haptic effectiveness of the scheme, which can be applied to the development of other haptic dampers that require variable damping. [ABSTRACT FROM AUTHOR]

To solve the problems of poor transmission performance and small torque regulation range of traditional MR device, a variable working gap MRF transmission device driven by electromagnetic force is proposed. The device uses electromagnetic force driving the squeeze disk to move axially to squeeze the MRF, thereby changing the number of working gaps and effective working thickness of the MRF to improve the transmission performance of the MR device. Based on the coil magnetization effect, the relationship between current, magnetic field intensity, and electromagnetic force is established. According to the driving characteristics of electromagnetic force and the rheological characteristics of MRF, a nonlinear function relationship between electromagnetic force and MRF working gap thickness and working volume is derived. Using the finite element method, a theoretical analysis of the magnetic circuit design, magnetic field distribution and temperature change profile in different parts of MRF device with different currents was conducted, the MRF torque transfer equations were deduced and calculated, and experimentally verified the correctness of the theoretical equations. Finally, the transmission performance of the variable working gap MRF transmission device is tested through the established testing system. Results show that, the required squeeze force is 6.65 kN when the MRF thickness reaches 1 mm in both working gaps. As the current increases from 0.5 to 3.0 A, the electromagnetic force increases from 0.65 to 6.77 kN, with an increase of 972.3%, the average temperature of the MRF in working gap I increases from 25.2°C to 71.2°C and the MRF in working gap II increases from 23.5°C to 48.3°C. When the current is 1.5 A, the MRF in the working gap I reaches magnetic saturation, continue to increase the current to 3.0 A, the MRF thickness in both working gaps is 1 mm, and the MR device transmits torque reach 376.6 N·m, which is 72.3% higher than that of the traditional MR device. [ABSTRACT FROM AUTHOR]

Finishing of femoral knee joint implant is very cumbersome due to its freeform nature. In the present study, a magnetic field-assisted finishing process is employed to uniformly finish the femoral knee implant over its surface curvature at the nanometer level. Experiments are conducted to analyze the freeform surface finishing capability of magnetic field-assisted finishing tool, which proves the tool's capability to achieve the required surface properties of a femoral knee implant. A comparative analysis between the performance of the magnetic field assisted finishing process and manually polished surface relative to tibial bearing material, that is, ultra-high molecular weight polyethylene with the help of pin-on-disc tribometer, is carried out. It will help to understand the in vivo performance of a finished femoral component of the knee joint by a magnetic field-assisted finishing process. The wear tests prove that the volume loss of the disc material while considering magnetic field-assisted finished pins (11.79 mm3) are better in all cases than the manually polished pins (27.97 mm3). The tribology test also demonstrates that femoral knee implant polished using magnetic field-assisted finishing process will face fewer problems related to wear debris. It will also reduce the problems that occur due to the mixing of debris in the bloodstream. The polishing tool provides almost uniform nanometer-level surface finishing with a standard deviation of 19.23 along the surface curvature. The minimum achieved surface roughness of the femoral knee joint is 20 nm. [ABSTRACT FROM AUTHOR]

This article focuses on modelling and validating a groundbreaking magnetorheological braking system. Addressing shortcomings in traditional automotive friction brake systems, including response delays, wear, and added mass from auxiliary components, the study employs a novel brake design combining mechanical and electrical elements for enhanced efficiency. Utilizing magnetorheological (MR) technology within a motor–brake system, the investigation explores the influence of external magnetic flux from the nearby motor on MR fluid movement, particularly under high-flux conditions. The evaluation of a high-magnetic-field mitigator is guided by simulated findings with the objective of resolving potential issues. An alternative method of resolving an interaction between an electric motor and a magnetorheological brake is presented. In addition, to test four configurations, multiple absorber materials are reviewed. [ABSTRACT FROM AUTHOR]

This study explores the significance of active suspension systems for vehicles with lower chassis compared to conventional ones, aiming at the development of future automobiles. Conventional linear MR (magnetorheological) dampers were found inadequate in ensuring sufficient vibration control because the vehicle's chassis becomes lowered in the unmanned vehicles or purposed-based vehicles. As an alternative, a rotary type of MR damper is proposed in this work. The proposed damper is designed based on prespecified design parameters through mathematical modeling and magnetic field analyses. Subsequently, a prototype of the rotary MR damper identical to the design is fabricated, and effectiveness is shown through experimental investigations. In configuring the experiments, a proportional-integral (PI) controller is employed for current control to reduce the response time of the damper. The results presented in this work provide useful guidelines to develop a new type of MR damper applicable to various types of future vehicles' suspension systems with low distance from the tire to the body floor. [ABSTRACT FROM AUTHOR]

MR fluid, a typical non-Newtonian fluid, has shear-thinning characteristics, which is shown that the shear stress increases non-linearly with the shear rates. To be more precise, shear stress increases with shear rates but its increasing rate gradually slows down. The broken particle chains after shear rotate at the same velocity as the upper shear disk, and there is a velocity difference with base carrier fluid, resulting in a hydrodynamic force. Besides, the particles at the end of rotating particle chains move outward by centrifugal force, which increases the rotating radius. At the same time, the angular velocity also increases with shear rates. With the combination of these two effects, the linear velocity of rotating particles increases exponentially, causing a higher hydrodynamic force. When the hydrodynamic force is higher than the magnetic force, the particle will fall off. As fewer particles rotate with the upper shear disk, the shear stress increases nonlinearly with the shear rate. The higher particle concentration will lead to more serious shear-thinning effects, while the increasing magnetic field strength will weaken it. The experiment results confirm that the mechanism of shear-thinning effects of MR fluid is particle chains breaking off. This work will provide guidance for the preparation of MR fluids, which is beneficial to improve the performance of MR fluids, as well as the precise control of MR devices. [ABSTRACT FROM AUTHOR]

Magnetorheological fluids (MRFs) are functional fluids that exhibit rapid and reproducible rheological responses to external magnetic fields. An MRF has been utilized to develop a haptic device with precise haptic feedback for teleoperative surgical systems. To achieve this, we developed several types of compact MRF clutches for haptics (H-MRCs) and integrated them into a twin-driven MRF actuator (TD-MRA). The first TD-MRA prototype was successfully used to generate fine haptic feedback for operators. However, undesirable torque ripples were observed due to shaft misalignment and the low rigidity of the structure. Additionally, the detailed torque control performance was not evaluated from both static and dynamic current inputs. The objective of this study is to develop a second prototype to reduce torque ripple by improving the structure and evaluating its static and dynamic torque performance. Torque performance was measured using both constant and stepwise current inputs. The coefficient of variance of the torque was successfully reduced by half due to the structural redesign. Although the time constants of the H-MRC were less than 10 ms, those of the TD-MRA were less than 20 ms under all conditions. To address the slower downward output response, we implemented an improved input method, which successfully halved the response time.

The coating effect of 1,2-bis(triethoxysilyl)ethane (BTES) on carbonyl iron particles (CIPs) was enhanced by etching with hydrochloric acid (HCl) of various concentrations, and magnetorheological fluids (MRFs) with significantly improved dispersion stability were obtained. The microstructures, coating effect, and magnetism of CIPs were examined using scanning electron microscopy (SEM), automatic surface and porosity analysis (BTE), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and a vibrating sample magnetometer (VSM), respectively. Furthermore, the rheological properties and dispersion stability of the MRFs were assessed by a rotating rheometer and a Turbiscan Tower. The results show that as the HCl concentration increased, nanopores appeared on CIPs and then disappeared, and the specific surface area of the particles increased and then decreased. When the concentration of HCl was 0.50 mol/L, the number of nanopores and the specific surface area of particles changed sharply. Not only that, the coated mass of BTES increased greatly and the saturation magnetization of particles decreased sharply. As the coated mass increased, without a magnetic field, the viscosity and shear stress of the MRFs increased, especially when the coated mass was more than 2.45 wt.%; while under a magnetic field, the viscosity and shear stress decreased, and the sedimentation rate of the MRFs decreased from 0.13 to 0.01 mm/h. By controlling the concentration of HCl for etching, the coating effect of CIPs was greatly enhanced, and thus an MRF with superior shear stress and excellent dispersion stability was obtained, which is significant in basic research and MRF-related applications.

The present study investigated the influence of magnetorheological (MR) fluid pocket configuration and magnetic field intensity on the dynamic response of the composite sandwich beam under various boundary conditions. The classical beam theory is used to develop the finite element (FE) formulations for the composite sandwich beam element and it is validated with the available literature. Four MR fluid pocket configuration types are considered. The configuration types include 1/4th, 1/2th, 3/4th and the full length of the MR fluid pockets at different locations. Further, a detailed study of the influence of each MR fluid pocket configuration type on the natural frequency, loss factor, and frequency response are presented. The maximum 32.27% of deviation in the first fundamental frequency is observed for the simply-supported boundary condition. From the results obtained, it is concluded that the length and location of the MR fluid pocket have a considerable impact on the dynamic response and also observed that the effect of the configuration depends on the type of boundary condition used. [ABSTRACT FROM AUTHOR]

Poppet valves used in internal combustion engines have a high risk of failure due to significant temperature and pressure. These poppet valves need surface finishing at the nano-scale level to prolong their life during their working use. In the present research, the chosen poppet valve has narrow ridge profiles, which is difficult to nano-finish by conventional processes due to certain limitations. The magnetorheological fluid-based finishing method can be effectively used for this kind of complicated narrow profile. For the magnetorheological fluid-based finishing processing of the poppet valve, a novel magnet fixture and setup is used. For checking the efficiency of this setup, surface characterization and surface roughness for polished and unpolished surfaces are outlined using a field-emission scanning electron microscope, microscope and optical profilometer. The final surface roughness of Sa = 23.1 nm at poppet profiles were obtained. All manufacturing defects like burrs, dents, scratches and pits are almost removed. The study of finishing forces in the magnetorheological fluid-based finishing method is also carried out using magnetostatic fluid–solid interaction, experimental and theoretical analysis. This force analysis supports the development of the material dislodgement model to anticipate material removal rate while finishing. The gap (error = 12.87%) between the experimental and theoretical material removal rate is marginal. It has high accuracy and reliability for specific applications. [ABSTRACT FROM AUTHOR]

The settling stability of magnetorheological fluid (MRF) is an important aspect of magnetorheological research and an important indicator of MRF quality. The discrete element method (DEM) was proposed to study the multi-particle settling process of particles dispersed in silicon oil with different iron powder content, particle size, base viscosity, and added magnetic field. Then by preparing MRF, the zero-field viscosity, dynamic magnetic field viscosity, and settling stability of various MRF were measured and analyzed. The results show that the average kinetic energy of MRF settling decreases as particle content, particle size, and base fluid viscosity increase. With 50% iron powder content, 300 nm particle size, and 5% bentonite additive, MRF has the highest viscosity under zero field; under a dynamic magnetic field, the larger the particle size, the larger the viscosity; the MRF settling rate decreases by 18% with a change in iron powder content, decreases by 22.5% with a change in particle size to 300 nm, and decreases by 22% with a change in bentonite content. Under the application of a magnetic field, MRF hardly settles. The final experimental and simulation results are comparable, indicating that the MRF settlement characteristics can be predicted to some extent with the help of DEM simulation. [ABSTRACT FROM AUTHOR]

Electric and magnetic fields have been used in various ways to enhance the performance of lubrication systems. The presence of these fields can significantly change the properties of lubricants. The rapid adoption of electric vehicles (EVs) has presented newlubrication-related challenges due to the presence of electric current. There is an urgent need for an in-depth study of lubrication systems subjected to such fields. This paper highlights recent research works on several key areas of lubrication involving electric or magnetic fields, which are:1) electric double layer in lubrication, 2) electrorheological fluids, 3) magnetorheological fluids, 4) ferrofluids, and 5) typical fluids used in the current EVs and typical surface failures of bearing components in EVs. Commonly used lubricants in each area are reviewed; lubrication mechanisms and related mathematical models are summarized; methods for and results from numerical analyses and experimental explorations are discussed; and common features of lubrications in different fields are explored. Based on the current research progress in these fields and the classic generalized Reynolds equation, a generalized mechanical-electro-magnetic-thermal-field (MEMT-field) Reynolds equation is proposed to describe the aforementioned lubrication scenarios and the effects of coupled mechanical, electric, magnetic, and thermal fields, which can be solved with a numerical iteration method. [ABSTRACT FROM AUTHOR]

Magnetorheological Transmission Device (MRTD) is a controllable power regulation device using magnetorheological fluid as the transmission medium. It has characteristics of fast response, a wide range of speed regulations, and a pollution-free environment. The traditional pairwise transmission structure has serious heat generation problems during operation, resulting in low transmission efficiency. Therefore, we innovatively propose a multi-stage roller type MRTD to improve the heat generation problem fundamentally. The steady-state and transient temperature fields of the multi-stage roller type MRTD are simulated using the thermal analysis module in ANSYS based on the temperature field formulation. The variations of internal temperature at different slip powers are obtained. The results show that the designed multi-stage roller type MRTD has a good suppression of temperature rise. This study can provide a new approach to improve the thermal performance of MRTD. [ABSTRACT FROM AUTHOR]

In order to address the problems of insufficient load capacity and rotor vibration, an active fluid-film bearing lubricated with magnetorheological fluid (MRF) is proposed. First, the geometry of the MRF fluid-film bearing is designed and its intelligent lubrication mechanism is analyzed to clarify its advantages. In addition, mathematical model of MRF fluid-film bearing-rotor system is derived, and FEM model is utilized to obtain stiffness and damping coefficients to supplement mathematical model. Moreover, an improved gray wolf optimization (IGWO) algorithm is developed to tune the PID controller parameters. The validity of the proposed method is verified by numerical simulation. Furthermore, the simulation results show that with the increasing of current magnitude, the orbits of shaft center decrease. Under the presence of magnetic fields, the shaft center orbits of the MRF bearing can converge to a point, and therefore this bearing has ability to suppress rotor vibration. Finally, IGWO-PID controller has better response characteristics than GWO, PSO, and GA algorithms, and hence the IGWO algorithm can find the more appropriate PID controller parameters, that the validity of the improved algorithm is further proved. Therefore, the active bearing and its research findings provide new reference for MRF vibration control in the field of journal bearing lubrication. [ABSTRACT FROM AUTHOR]

Magnetorheological (MR) fluids have been known to react to magnetic fields of sufficient magnitudes. While in the presence of the field, the material develops a yield stress. The tunable property has made it attractive in, e.g., semi-active damper applications in the vibration control domain in particular. Within the context of a given application, MR fluids can be exploited in at least one of the fundamental operating modes (flow, shear, squeeze, or gradient pinch mode) of which the gradient pinch mode has been the least explored. Contrary to the other operating modes, the MR fluid volume in the flow channel is exposed to a non-uniform magnetic field in such a way that a Venturi-like contraction is developed in a flow channel solely by means of a solidified material in the regions near the walls rather than the mechanically driven changes in the channel's geometry. The pinch-mode rheology of the material has made it a potential candidate for developing a new category of MR valves. By convention, a pinch-mode valve features a single flow channel with poles over which a non-uniform magnetic field is induced. In this study, the authors examine ways of extending the dynamic range of pinch-mode valves by employing a number of such arrangements (stages) in series. To accomplish this, the authors developed a prototype of a multi-stage (three-stage) valve, and then compared its performance against that of a single-stage valve across a wide range of hydraulic and magnetic stimuli. To summarize, improvements of the pinch-mode valve dynamic range are evident; however, at the same time, it is hampered by the presence of serial air gaps in the flow channel. [ABSTRACT FROM AUTHOR]

This study proposes two adaptive controllers and applies them to the vibration control of an in-wheel motor vehicle’s (electric vehicle) suspension system, in which a semi-active magnetorheological (MR) damper is installed as an actuator. As a suspension model, a nonlinear quarter car is used, providing greater practical feasibility than linear models. In the synthesis of the controller design, the values of the sprung mass, damping coefficient and suspension stiffness are treated as bounded uncertainties. To take into account the uncertainties, both direct and indirect adaptive sliding mode controllers are designed, in which the principal control parameters for the adaptation law are updated using the auto-tune method. To reflect the practical implementation of the proposed controller, only two accelerometers are used, and the rest of the state values are estimated using a Kalman observer. The designed controller is applied to a quarter car suspension model of an in-wheel motor vehicle featuring an MR damper, followed by a performance evaluation considering factors such as ride comfort and road holding. It is demonstrated in this comparative work that the proposed adaptive controllers show superior control performance to the conventional proportional–integral–derivative (PID) controller by reducing the vibration magnitude by 50% and 70% for the first and second modes, respectively. In addition, it is identified that the second mode (wheel mode) of the in-wheel motor vehicle is more sensitive than the first body mode depending on the mass ratio between the sprung and unsprung mass.