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This study introduces an innovative master-slave cardiac ablation catheter robot system that employs magnetorheological fluids. The system incorporates magnetorheological fluid to enable collision detection through haptic feedback, thereby enhancing the operator's situational awareness. A modular clamping and propulsion mechanism has been engineered for the ablation catheter, facilitating omnidirectional operation and force feedback within the cardiac cavity. To evaluate the proposed system, an in vitro experiment was performed. Results from the experiment indicate that the system demonstrates high motion transmission accuracy. Furthermore, the system effectively alerts operators to potential collisions, enabling swift catheter position adjustments, minimizing the risk of vascular perforation, and ultimately enhancing the overall safety and efficiency of the procedure. [ABSTRACT FROM AUTHOR]

The 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]

This work focused on the development of a complete laboratory procedure for the rheological characterization of magnetorheological fluids (MRFs) by combining information gained from the literature and practical work performed in the laboratory. The procedure developed involves all the experimental stages for a comprehensive analysis, starting from the sample preparation, choice of the optimal measuring system, definition of the test, and rheometric parameters for the execution of an accurate and reliable analysis. Magnetorheology is a critical approach for studying the field-dependent properties of MRFs; however, measurement errors, often stemming from inappropriate rheometric test parameters, pose significant challenges. Additionally, sedimentation, caused by the large density mismatch between magnetic particles and the carrier fluid, presents a major obstacle that can compromise the analysis. Extensive work was performed for selecting the test parameters as well as defining the most relevant type of analysis to conduct with the defined procedure for the definition of the essential properties of an MRF for braking applications. This work is essential for the development of accurate card material for simulation tools, paving the way for broader utilization of MRFs in cutting-edge technologies. [ABSTRACT FROM AUTHOR]

Purpose: This research aims to propose and analyze a novel design for Rotary Magnetorheological Fluid Damper for Automotive suspension system applications. Due to development/variation in values of yield stress and viscosity give rise to opposing torque in MR fluid based Rotary damper, this can be utilized to redirect the forces which is approaching from the ground to wheel base and further to the chassis of the automobile vehicle in the form of torque and then dampen the vibrations ultimately reducing unpleasant ride or discomfort. Methods: The research will begin with identification of performance gap between conceptual and conventional design, then it progresses to literature survey followed by development of system level design and test rig design. Moreover, it evaluates the practical implementation of these dampers in automotive systems through extensive simulation and real-world testing. Once the test configuration had been developed, the final design were subjected to testing. The results of the study have been analyzed on the basis of different input frequencies provided to the test setup manufactured. Results: The concluded remarks with major inferences such as: percentage amplitude reduction is very high for operational frequencies and high torque output is obtained even with a simple topology of rotary MR damper in automotive applications. This research contributes to the development of intelligent, high-performance automotive systems that can meet the evolving demands of an advance transportation. [ABSTRACT FROM AUTHOR]

Magnetorheological (MR) fluids are utilized to develop a variety of electromechanical devices that have potential applications in the automotive, medical, aerospace, and other areas. Since yield stress is the most important design parameter of an MR fluid and its devices, it is dependent on the types of operational modes. This paper thoroughly examines the effects of the operational modes of MR fluids such as shear mode, and squeeze mode along with the impact of mixed-mode operation on the performance of MR fluids and devices. The study found that mixed-mode operation results in higher yield stress and offers better performance control for MR fluid devices compared to single-mode operation under the same working conditions. Several factors impact the performance of MR fluid devices in various operational modes discussed in the paper such as geometry, initial gap thickness, temperature, pressure, velocity, applied compressive strain, response time, magnetic particle composition, magnetic field, and other working factors. Therefore, there is a necessity to thoroughly examine the rheological and mechanical behaviors of MR fluids and the performance of MR devices in different operational modes and working circumstances, highlighting the experimental and theoretical findings conducted by researchers. [ABSTRACT FROM AUTHOR]

The magnetorheological (MR) damper is a by-wire system capable of providing variable damping stiffness by responding to an apparent magnetic field. In response to the magnetic field application, the magnetorheological fluid (MR fluid) exhibited altered behavior within the damper. Typically, a damper's internal and external valves operate in flow mode, where the flow is regulated by controlling the magnetic field. This study aims to investigate the performance characteristics of a small core annular and radial magnetorheological valve (SCARMV) designed for applications in vehicle suspension systems. The proposed design of the simplified MR valve is based on a meandering-type valve composed of multiple valve cores that have been simplified to a single core. Dynamic testing was performed on the proposed valve, which features a single rod tube damper, to investigate the damping force characteristics by varying currents and frequencies. The characteristics of the measured damping force were compared to the calculated damping force based on the pressure drop calculation and the FEMM simulation of magnetic flux. By increasing the stroke length of the valve travel is set to 10 mm at a current input of 0 A to 1.0 A, the maximum output of the MR valve damping force was approximately 1.57 kN. In addition, a mathematical model of SCARMV is presented and compared to the experimental data. Therefore, based on the experimental results, it was concluded that the usability of a compact core MR valve is reliable. However, more in-depth studies are required before these dampers can be applied to vehicle suspension systems. [ABSTRACT FROM AUTHOR]

The authors have investigated, with the rotational viscometer, the rheological characteristics of magnetorheological fluids with a dispersed phase both on the basis of particles of carbonyl iron only and with additions of a ferrimagnetic oxide filler. Flow curves obtained by regression-analysis methods have been approximated by a power function with three parameters dependent on the magnetic field strength and the concentration of the dispersed phase. [ABSTRACT FROM AUTHOR]

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]

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 utilization of magnetic nanofluids as the base carrier fluid of magnetorheological fluids represents an effective approach to enhance the magnetorheological effect. However, achieving highly stable nano-composite magnetorheological fluids remains a significant challenge, encompassing both the synthesis of magnetic nanofluids and the prevention of composite particle agglomeration. In this study, Fe3O4 silicone oil-based magnetic nanofluids were prepared using silane coupling agent KH550 as a dispersant, followed by a novel process of co-coating dispersants to obtain nano-composite magnetorheological fluids. The surface morphology, physical phase composition and magnetic properties were characterized and analyzed using XRD, FI-IR, TEM, FE-SEM and VSM. The sedimentation stability and redispersibility of the novel nano-composite magnetorheological fluids were investigated. The results show that surface modification of micron-sized particles significantly enhances the stability and redispersibility of the nano-composite magnetorheological fluids, with optimal sedimentation stability and redispersibility observed at nanoparticle volume fraction of 8%. Furthermore, the novel nano-composite magnetorheological fluids demonstrate superior temperature resistance, remaining stable within the temperature range form -40 °C to 120 °C over extended durations. Rheological properties of novel nano-composite magnetorheological fluid were also investigated demonstrating higher off-state viscosity and magnetorheological effect in comparison to conventional magnetorheological fluids. Moreover, both static and dynamic yield stresses increase with nanoparticle concentration and magnetic field strength. [ABSTRACT FROM AUTHOR]

A model medium of micrometer-sized magnetite particles and metal balls with a diameter of 1 mm in a viscous medium (glycerol) was studied. The processes of organization of this system in an increasing external magnetic field were considered. The effect of shear vibrations on the processes of structure formation in the systems under study was also examined. The data obtained can serve as a basis for modeling the dynamics of disperse systems and expanding the understanding of their behavior and organization in magnetic fields and under mechanical influences. [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]

The article provides theoretical substantiation for the necessity of analyzing the joint operation of the mechanical and hydraulic subsystems of a magnetorheological hydraulic anti-vibration mount (MR hydromount). Experimental studies are conducted on MR hydromounts OGM-95 with a low eigenfrequency. It is confirmed that the mechanical and hydraulic subsystems of MR hydromounts require configuration in order to achieve the greatest vibration damping in the pre-resonance frequency region. The mounts are controlled by synchronous configuration of the phase and frequency of the control signal of the magnetorheological transformer with the fundamental oscillations harmonic reaching the frequency of mechanical resonance of the MR hydromount. [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]

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]

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.

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.

This work focused on the development of a complete laboratory procedure for the rheological characterization of magnetorheological fluids (MRFs) by combining information gained from the literature and practical work performed in the laboratory. The procedure developed involves all the experimental stages for a comprehensive analysis, starting from the sample preparation, choice of the optimal measuring system, definition of the test, and rheometric parameters for the execution of an accurate and reliable analysis. Magnetorheology is a critical approach for studying the field-dependent properties of MRFs; however, measurement errors, often stemming from inappropriate rheometric test parameters, pose significant challenges. Additionally, sedimentation, caused by the large density mismatch between magnetic particles and the carrier fluid, presents a major obstacle that can compromise the analysis. Extensive work was performed for selecting the test parameters as well as defining the most relevant type of analysis to conduct with the defined procedure for the definition of the essential properties of an MRF for braking applications. This work is essential for the development of accurate card material for simulation tools, paving the way for broader utilization of MRFs in cutting-edge technologies.

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]

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]

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 this study, Magnetorheological (MR) finishing fluid samples have been synthesized and experiments have been conducted to investigate the rheological properties namely off-state viscosity and on-state yield stress of prepared samples. The compositions of the MR finishing fluid havebeen determined by using Taguchi based design of experiment approach. The MR properties have been characterized on a rheometer, using MR device accessory. Bingham Plastic, Casson fluid and Herschel Bulkley are the three fluid models utilized for the modelling of the fluid. The Hershel--Bulkley model has resulted as the most apposite model for fluid with the highest coefficient of regression (R2) value i.e., 0.9049. Further, Technique for order of preference by similarity to ideal solution (TOPSIS) has also been utilized to establish the effect of its constituents on both the considered rheological properties. To determine the magnetic saturation of the developed MR finishing fluid, graphs between magnetic field strength and on-state yield stress have been plotted. Analysis of Variance (ANOVA) publicized the weight percentage of Fe powder as the most notable parameter, contributing 66.12% followed by the weight percentage of SiC abrasives with 8.09%. The MR finishing fluid samples have attained the highest yield stress at magnetic field intensity of around 0.7 Tesla, which is considered as the limiting value for the finishing process. The optimized fluid sample has been used for finishing 2 mm hole using an indigenously developed finishing process. [ABSTRACT FROM AUTHOR]

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]

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]