Magnetorheological Fluid Technology Research Articles

Magnetorheological fluid in prostheses: A state-of-the-art review

Magnetorheological fluids (MRF) are intelligent materials that can vary their yield stress in response to an applied magnetic field. This characteristic, combined with active and multifunctional control, allows the development of actuators with fast response time, low energy consumption, long service life, and reduced dimensions and weights. Various studies have been conducted to improve MR dampers in prosthetic applications, including knees, ankle-foot, hands, and sockets. Here, we present a critical review of the progress of MRFs in the prosthetic field. In addition, research in prostheses’ design, optimization, and control of magnetorheological actuators is investigated, along with MRF modeling, mode of operation, type of MR actuator, classification, and working principle of MRF-based devices. Although MRFs are considered promising materials for designing novel prosthetic devices, this review shows that applications have been predominantly focused on lower limb prostheses. We conclude by discussing possible future applications and challenges that must be faced to enable and improve commercial applications based on MRF technology.

Thermal Conductivity and Temperature Dependency of Magnetorheological Fluids and Application Systems-A Chronological Review.

Many studies on magnetorheological fluid (MRF) have been carried out over the last three decades, highlighting several salient advantages, such as a fast phase change, easy control of the yield stress, and so forth. In particular, several review articles of MRF technology have been reported over the last two decades, summarizing the development of MRFs and their applications. As specific examples, review articles have been published that include the optimization of the particles and carrier liquid to achieve minimum off-state viscosity and maximum yield stress at on-state, the formulation of many constitutive models including the Casson model and the Herschel-Bulkley (H-B) model, sedimentation enhancement using additives and nanosized particles, many types of dampers for automotive suspension and civil structures, medical and rehabilitation devices, MRF polishing technology, the methods of magnetic circuit design, and the synthesis of various controllers. More recently, the effect of the temperature and thermal conductivity on the properties of MRFs and application systems are actively being investigated by several works. However, there is no review article on this issue so far, despite the fact that the thermal problem is one of the most crucial factors to be seriously considered for the development of advanced MRFs and commercial products of application systems. In this work, studies on the thermal conductivity and temperature in MRFs themselves and their temperature-dependent application systems are reviewed, respectively, and principal results are summarized, emphasizing the following: how to reduce the temperature effect on the field-dependent properties of MRFs and how to design an application system that minimizes the thermal effect. It is noted here that the review summary is organized in a chronological format using tables.

An optical red green blue sensor for monitoring the degradation of magnetorheological fluids in flow-recirculating high-torque clutch actuators

The aerospace industry is gradually moving toward “more electric aircraft” to reduce its environmental footprint. Developing all-electric actuators brings a reliability challenge because conventional geared-motor actuators are susceptible to jamming failures from their metal-to-metal gear contacts. Magnetorheological clutch actuators solve this challenge using a layer of fluid to transmit torque and are not exposed to potential jam failures, making them particularly attractive for high reliability applications such as primary flight controls. A key challenge that must be addressed for a widespread deployment of the magnetorheological fluid technology in aerospace is the ability to monitor magnetorheological fluid condition while it degrades in operation. To date, no such efforts have been reported in the literature. Recent studies on magnetorheological fluid durability have shown that mixing the magnetorheological fluid using a magnetic screw pump principle can significantly increase the life of the fluid by up to 50%. This article presents the design, prototyping, and testing of a proof-of-concept magnetorheological fluid condition monitoring sensor, capitalizing on the flow-recirculating properties of magnetic screw magnetorheological clutches to continuously provide a well-mixed and homogeneous fluid sample to the sensor. The proposed sensing principle uses optical red green blue sensor placed in the fluid circulation path to measure the fluid color during degradation. The sensor has been tested up to fluid failure on a high-torque (60 N m) magnetorheological clutch mounted on a fully instrumented durability test bench. Tests have been performed with two types of fluid: a commercially available fluid, the Lord 140CG, and a homemade fluid based on perfluoropolyether oil, the GPL-103. Results with the Lord fluid demonstrate a strong correlation between the decrease in torque-to-current performance with fluid brightness. The average of three aging tests on Lord 140CG fluid show a 12% ± 1% decrease in brightness at end-of-life regardless of operating conditions such as torque, shear rate, and dissipated power. These results suggest that, for the Lord 140CG fluid, brightness is directly linked to the fluid degradation state and independent of operating conditions, which makes it a more accurate metric to quantify durability than life dissipated energy since the latter can vary significantly depending on operating conditions. Tests made with the GPL-103 based fluid did not show such a strong correlation, which means that optical sensing of magnetorheological fluid condition must be carefully calibrated for each individual fluid and clutch design. Results from this study suggest that optical sensing is a relevant method to measure the magnetorheological fluid condition in flow-recirculating clutches.

Magneto-rheological defects and failures: A review

Magneto-rheological fluid is the colloidal suspension of micron sized magnetic particles in a carrier fluid where defects and failures occur at many circumstances. This paper presents a review on defects and failures of magneto-rheological fluid in engineering applications. The most significant defect is hard cake which developed due to re-dispersion difficulties of remnant particles magnetization, leaving the magneto-rheological fluid ineffective. Clumping effect on the other hand is a separation of carrier fluid from the magnetic particles when magneto-rheological fluid is being exposed to higher magnetic field for an extended period of time. As clumping occurred, it leads to Fluid Particle Separation (FPS) which is believed altering the strength distribution of magneto-rheological fluid and therefore reducing the squeezing force. Another significant failure is magnetic particles oxidation of the magneto-rheological fluid. This paper also will discuss on stability problems which is the most challenged issue in magneto-rheological fluid technology. With the comprehensive review in this paper, researcher can design materials of magneto-rheological fluid for better properties.

"Introduction to Magneto-Rheological Fluid Technology & Its Application"

"Introduction to Magneto-Rheological Fluid Technology & Its Application"

A review on the magnetorheological fluid preparation and stabilization

Abstract Magnetorheological fluids (MRFs) are one of the categories of smart materials, whose viscosity increases considerably in the presence of a magnetic field. These fluids are prepared by dispersing magnetizable micro-size particles into a carrier fluid with stabilizer additives. The main feature of these fluids is their ability to change from liquid to semi-solid state with controllable yield stress just a few milliseconds after applying a magnetic field. Low magnetorheological effect and instability of MRFs are the most important problems against the extensive application of MRFs technology in modern industries. Various methods have been proposed and used by researchers to improve the magnetorheological effect and also the stability of these fluids. The main focus of this study is to present a comprehensive review on different methods of preparation and stabilization of MR fluids. Furthermore, rheological models and application of MR fluids are discussed briefly in this study.

Investigation of Annular Gap Size for Optimizing the Dynamic Range of MR Damper Using Comsol Multiphysics Software

Magneto-rheological (MR) fluid technology has made it possible to develop reliable, revolutionary vibration control systems for a variety of commercial, medical and military applications. MR fluid shock absorber systems are enabled by remarkably versatile MR fluid technology, which allows the system to respond instantly and controllably to varying levels of vibration or shock with simple, robust designs. This paper presents a parametric study of the MR dampers for semi-active vibration control. The influence of gap size of the damper on the viscous stress of the MR fluid is examined. It is inferred from the study that the viscous stress of the MR fluid for different parameters such as gap size influences the dynamic range of MR fluid dampers.The simulated results depict a maximum viscous stress of 1765.441 N/m2for a gap size of 1.85 mm. The developed dynamic range would allow for smaller size of the device, higher dynamic yield stress and low power consumption. The simulated results using COMSOL multiphysics for the verification of the parametric strategy have been presented. Results of this study shall enhance the design of MR dampers for different control applications.

Magnetorheological fluid dampers: A review on structure design and analysis

Magnetorheological fluid technology has gained significant development during the past decades. The application of magnetorheological fluids has grown rapidly in civil engineering, safety engineering, transportation, and life science with the development of magnetorheological fluid–based devices, especially magnetorheological fluid dampers. The magnetorheological fluid dampers could offer an outstanding capability in semiactive vibration control due to excellent dynamical features such as fast response, environmentally robust characteristics, large force capacity, low power consumption, and simple interfaces between electronic input and mechanical output. To address the fast growing demand on magnetorheological fluid damping technology in extensive engineering practices, the state-of-the-art development is presented in this article, which provides a comprehensive review on the structure design and its analysis of magnetorheological fluid dampers (or systems). This can be regarded as a useful complement to several existing reviews in the recent literature on magnetorheological fluids technology, magnetorheological fluid applications, modeling of magnetorheological fluids and dampers, control strategies of magnetorheological fluid systems, and so on. The review begins with an introduction of the basic features and relevant applications of magnetorheological fluids. Then several basic structure design issues of magnetorheological fluid dampers are introduced. Following this, typical magnetorheological dampers are discussed according to the arrangement configurations of magnetorheological fluid cylinders and magnetorheological fluid control valves. Furthermore, reinforced structure designs of magnetorheological fluid dampers are provided, which focus on coil configuration, fluid resistance channel design, and electromagnetic design. Thereafter, design issues of magnetorheological fluid damper systems are discussed, which involves sensor-based magnetorheological fluid damper systems, self-powered magnetorheological fluid damper systems, fail-safe magnetorheological fluid damper systems, and integrated spring magnetorheological fluid damper systems. Importantly, to have a systematic quantitative viewpoint of the analysis and design of magnetorheological fluid dampers, the review ends with a summary of performance analysis issues, including performance specification, analytical modeling, parameter optimization, and so on.

Shear and Squeeze Rheometry of Magnetorheological Fluids

The mechanical properties of a magnetorheological (MR) fluid in shearing, compression and shearing after compression have been studied in the magnetic field which is generated by a coil carrying different magnitudes of DC electrical current on a self-constructed test system. The relations of compression stress versus compression strain, yield stress versus compression stress were studied under different magnetic fields. The compressing tests showed that the MR fluid is very stiff at small compressive strains lower than 0.13. The shear yield stress of MR fluids after compression was much stronger than that of uncompressed MR fluids under the same magnetic field. The enhanced shear yield stress of MR fluids can be utilized to design the MR clutch and brake for new structure and will make MR fluids technology attractive for many applications.

Development of a Variable Stiffness and Damping Isolator Using Magnetorheological Fluid Technology

This paper presents the development of a variable stiffness and damping isolator using magnetorheological (MR) fluid technology. The MR fluid isolator is composed of two variable volume rubber bladder filled with MR fluid, a pipe and a MR valve connecting them. One of the bladders supports disturbance force and the MR fluid flows between two bladders because of the variation of bladder volume due to deformation. The shear stress of the MR fluid in MR valve is varied by an applied magnetic field, which thereby varies the characteristics of the isolator, such as its stiffness and damping. A mathematical model of the isolator was derived, and a prototype of the MR fluid bladder spring was fabricated and its dynamic behavior was measured in vibration force for a wide range of frequencies under various applied magnetic fields. The parameters of the model under various magnetic fields were calculated and the bladder dynamic performances were evaluated. A non-resonant control was employed to minimize the vibration amplitude of the system. Numerical simulation results indicated that the semiactive control system produced much better isolation performance than a passive system.

Against the flow [smart fluids

An interesting feature of Audi's new TT vehicle is its semi-active primary suspension system enabled by magneto-rheological (MR) fluid technology that allows continuously variable real-time suspension damping control. The suspension system is supplied by Delphi Corp. and is based on technology from Lord Corp. Although it can be used for other applications including seismic damping in buildings, damping of bridges against strong winds, and controlled dampers in prosthetic devices designed to provide users with tactile feedback, MR fluid technology's main market is the auto suspension system. MR-based components are now operating in hundreds of thousands of vehicles all over the world.

Design and application of magneto-rheological fluid

Magneto-rheological fluid (MRF) technology is an old “newcomers” coming to the market at high speed. Various industries including the automotive industry are full of potential MRF applications. Magneto-rheological fluid technology has been successfully employed already in various low and high volume applications. A structure based on MRF might be the next generation in design for products where power density, accuracy and dynamic performance are the key features. Additionally, for products where is a need to control fluid motion by varying the viscosity, a structure based on MRF might be an improvement in functionality and costs. Two aspects of this technology, direct shear mode (used in brakes and clutches) and valve mode (used in dampers) have been studied thoroughly and several applications are already present on the market. Excellent features like fast response, simple interface between electrical power input and mechanical power output, and precise controllability make MRF technology attractive for many applications. This paper presents the state of the art of an actuator with a control arrangement based on MRF technology. The study shows that excellent features like fast response, simple interface between electrical power input and the mechanical power output, and controllability make MRF the next technology of choice for many applications.

MAGNETORHEOLOGICAL (MR) FLUID AND ITS APPLICATIONS

Magnetorheological (MR) fluid is a functional, smart or controllable fluid, which responds to magnetic field, changing its rheological properties. The increased resistance to flow of an MR fluid is proportional to the strength of magnetic fi eld. A typical MR fluid consists of iron particles, suspended in a carrier liquid such as synthetic oil or water. Proprietary additives, to discourage gravitational settling and promote particle suspension, are added to enhance lubricity, modify viscosity, and inhibit wear. In recent years devices and systems using MR fluid technology have been commercialized across wide industry applications, including automotive, industrial and civil engineering. In that development two key issues for the commercial success of MR fluid technology-durability and settling-have shown continual improvement as a result of formulation research. As a result, MR fluids today are strong, durable, adaptable and highly developed with fundamental material data and device design and models.