Search Results (533)

Magnetorheological elastomers (MREs) are a type of smart materials formed by dispersing magneto-responsive micron particles in an elastic polymer matrix. They hold significant potential for various applications due to their tunable stiffness, capability to carry out non-contact actuation, and rapid responsiveness to magnetic fields. However, weak interfacial interactions and poor dispersion of magnetic particles within the polymer matrix often lead to diminished magnetorheological (MR) performance. In this study, carbonyl iron powder (CIP) was chemically modified via polydopamine (PDA) deposition followed by grafting with isobutyl (trimethoxy)silane (IBTMO) to enhance its compatibility with a silicone-based matrix. The resulting anisotropic MREs fabricated using the dual-modified CIP exhibited a reduced elastic modulus, enhanced elongation, a large magnetically induced bending angle of 38°, and a notably improved MR effect of 246.8%. Furthermore, a magnetic soft actuator was designed based on the anisotropic dual-modified CIP-based MRE. When used as flippers for a duck model, the actuator successfully propelled a load approximately 76.8 times its own weight at a speed of 3.48 mm/s, thereby demonstrating promising potential for applications requiring load-bearing actuation. Full article

Magnetorheological fluid exhibits shear-thinning behavior when subjected to high temperature environments exceeding 100 °C, which will significantly compromise the operational stability and reliability of the associated mechanical systems. To enhance the performance of magnetorheological fluid, this study selects soft magnetic particles, base carrier fluid, and surfactants based on their resistance to high temperatures and shear-thinning effects. A novel magnetorheological fluid with enhanced thermal stability and shear stability is subsequently developed by carefully selecting flake-shaped carbonyl iron powder, dimethyl silicone oil, and surfactant exhibiting both sedimentation stability and high temperature resistance. The apparent rheological properties and mechanical performance of the fluid are systematically evaluated. Experimental results indicate that the sedimentation rate of the prepared magnetorheological fluid is 3.86% after standing for 10 days, the thermal expansion rate at 200 °C is 12.8%, and the evaporation rate following repeated high temperature applications is only 0.66%. The shear yield stress of the prepared magnetorheological fluid is 31.2 kPa under the magnetic field of 817 mT. The prepared magnetorheological fluid demonstrates excellent thermal stability and shear-thinning resistance, which holds significant potential for enhancing the performance of magnetorheological devices in future applications. Full article

With the increasing requirements for speed and travel distance in tracked vehicles on various terrains and the increasing mass ratio of powertrains, the vibration problem of high-power powertrains becomes a critical challenge. In this paper, in order to reflect on the vibration transmission relationship between the powertrain and the complex carrier, the magnetorheological damping system of a powertrain is studied in a whole vehicle model. The transfer matrix and equations of each component, including the magnetorheological mount, are derived by the Rui Method. Then, the electromechanical coupling multibody dynamic model of the vehicle–powertrain magnetorheological damping system is established. Consequently, the fast solution of vehicle–powertrain vibration characteristics under various road excitations is realized. The dynamic and static coupling characteristics of the powertrain system and the factors affecting its performance are analyzed in a moving vehicle. The simulation results indicate that the vibration reduction performance is the worst in the X-direction, whereas the vibration reduction performance is the best in the Y-direction. Under the E-class road condition at 10 m/s, the RMS acceleration reduction in the powertrain is 41.63% in the Y-direction relative to the chassis. Both the resonant frequency of the powertrain and chassis are 86.93 Hz in the Y-direction. Finally, the accuracy of the results is verified by simulation and driving experiments. The research results can provide theoretical guidance for the design and optimization of the powertrain mount of a tracked vehicle. Moreover, it provides a new technical means of studying the vibration characteristics of a complex multibody system. The simulation results demonstrate notable directional variations in the vibration attenuation performance of the powertrain damping system. Specifically, the X-direction shows the poorest vibration attenuation, whereas the Y-direction exhibits the best damping characteristics. Full article

To improve both ride comfort and energy efficiency, this study proposes a semi-active suspension system equipped with an electromagnetic linear energy-regenerative magnetorheological damper (ELEMRD). The ELEMRD integrates a magnetorheological damper (MRD) with a linear generator. A neural network-based surrogate model was employed to optimize the key parameters of the linear generator for better compatibility with semi-active suspensions. A prototype was fabricated and tested. Experimental results show that with an excitation current of 1.5 A, the prototype generates a peak output force of 1415 N. Under harmonic excitation at 5 Hz, the no-load regenerative power reaches 11.1 W and 37.3 W at vibration amplitudes of 5 mm and 10 mm, respectively. An energy-regenerative magnetorheological semi-active suspension model was developed and controlled using a Linear Quadratic Regulator (LQR). Results indicate that, on a Class C road at 20 m/s, the proposed system reduces sprung mass acceleration and suspension working space by 14.2% and 7.5% compared to a passive suspension. The root mean square and peak regenerative power reach 49.8 W and 404.2 W, respectively. The proposed semi-active suspension also exhibits enhanced low-frequency vibration isolation, demonstrating its effectiveness in improving ride quality while achieving energy recovery. Full article

Magnetorheological fluids (MRFs) are multiphase materials whose viscosity can be controlled via magnetic fields. However, particle sedimentation undermines their long-term stability. This review examines stabilization strategies based on the interaction between ultrasonic waves and time-varying magnetic fields, analyzed through advanced mathematical models. The propagation of acoustic waves in spherical and cylindrical domains is studied, including effects such as cavitation, acoustic radiation forces, and viscous attenuation. The Biot–Stoll poroelastic model is employed to describe saturated granular media, while magnetic field modulation is investigated as a means to balance gravitational settling. The analysis highlights how acousto-magnetic coupling supports the design of programmable and self-stabilizing intelligent fluids for complex applications. Full article

In rotating machinery, the demands for torque sensor resolution and range in various torque measurements are becoming increasingly stringent. This paper presents a novel variable stiffness torque sensor designed to meet the demands for high resolution or a large range under varying measurement conditions. Unlike traditional strain gauge-based torque sensors, this sensor combines the advantages of torsion springs and magnetorheological fluid (MRF) to achieve dynamic adjustments in both resolution and range. Specifically, the stiffness of the elastic element is adjusted by altering the shear stress of the MRF via an applied magnetic field while simultaneously harnessing the high sensitivity of the torsion spring. The stiffness model is established and validated for accuracy through finite element analysis. A screw modulation-based angle measurement method is proposed for the first time, offering high non-contact angle measurement accuracy and resolving eccentricity issues. The performance of the sensor prototype is evaluated using a self-developed power-closed torque test bench. The experimental results demonstrate that the sensor exhibits excellent linearity, hysteresis, and repeatability while effectively achieving dynamic continuous adjustment of resolution and range. Full article

Magnetorheological fluids (MRFs) and elastomers (MREs) are two types of smart materials that exhibit modifiable rheological properties in response to an applied magnetic field. Although they share a similarity in their magnetorheological response, these two materials differ in their nature, structure, and mechanical behavior when exposed to a magnetic field. They also have distinct application differences due to their specific rheological properties. These fundamental differences therefore influence their properties and applications in various industrial fields. This review provides a synthesis of the distinct characteristics of MRFs and MREs. The differences in their composition, rheological behavior, mechanical properties, and respective applications are summarized and highlighted. This analysis will enable a comprehensive understanding of these differences, thereby allowing for the appropriate selection of the material based on the specific requirements of a given application and fostering the development of new applications utilizing these MR materials. Full article

The surface quality of biomedical implants, such as shoulder joint caps, plays a critical role in their performance, longevity, and biocompatibility. Most biomedical shoulder joints fail to reach their optimal functionality when finished through conventional techniques like grinding and lapping due to their inability to achieve nanometer-grade smoothness, which results in greater wear and friction along with potential failure. The advanced magnetorheological finishing (MRF) approach provides enhanced surface quality through specific dimensional control material removal. This research evaluates how MRF treatment affects the surface roughness performance and microhardness properties and wear resistance behavior of cobalt–chromium alloy shoulder joint caps which have biocompatible qualities. The study implements a magnetorheological finishing system built with an electromagnetic tool to achieve the surface roughness improvements from 0.35 µm to 0.03 µm. The microhardness measurements show that MRF applications lead to a rise from HV 510 to HV 560 which boosts the wear protection of samples. After MRF finishing, the coefficient of friction demonstrates a decrease from 0.12 to 0.06 which proves improved tribological properties of these implants. The results show that MRF technology delivers superior benefits for biomedical use as it extends implant life span and decreases medical complications leading to better patient health outcomes. The purposeful evaluation of finishing techniques and their effects on implant functionality demonstrates MRF is an advanced technology for upcoming orthopedic implants while yielding high precision and enhanced durability and functional output. Full article

This paper comprehensively reviews structural vibration control systems for earthquake mitigation in civil engineering structures. Structural vibration control is vital for enhancing the resilience and safety of infrastructure subjected to seismic activity. This study examines various control strategies, including passive, active, and hybrid methods, with a focus on the advantages of semi-active systems, which offer a balance of energy efficiency and adaptive capabilities. Semi-active devices, such as magnetorheological dampers, are highlighted for their ability to offer adaptive control without the high energy demands of fully active systems. The review discusses challenges like time delays, sensor placement, and model uncertainties that can impact the practical implementation of these systems. Experimental studies and real-world applications demonstrate the effectiveness of semi-active systems in reducing seismic responses. This paper emphasizes the need for further research into optimizing control algorithms and addressing practical challenges to enhance the reliability and robustness of these systems. It concludes that semi-active control systems are a promising solution for enhancing structural resilience in earthquake-prone areas, offering a practical alternative that strikes a balance between performance and energy requirements. Full article

Magnetorheological (MR) foams represent a class of smart materials with unique tunable viscoelastic properties when subjected to external magnetic fields. Combining porous structures with embedded magnetic particles, these materials address challenges such as leakage and sedimentation, typically encountered in conventional MR fluids while offering advantages like lightweight design, acoustic absorption, high energy harvesting capability, and tailored mechanical responses. Despite their potential, challenges such as non-uniform particle dispersion, limited durability under cyclic loads, and suboptimal magneto-mechanical coupling continue to hinder their broader adoption. This review systematically addresses these issues by evaluating the synthesis methods (ex situ vs. in situ), microstructural design strategies, and the role of magnetic particle alignment under varying curing conditions. Special attention is given to the influence of material composition—including matrix types, magnetic fillers, and additives—on the mechanical and magnetorheological behaviors. While the primary focus of this review is on MR foams, relevant studies on MR elastomers, which share fundamental principles, are also considered to provide a broader context. Recent advancements are also discussed, including the growing use of artificial intelligence (AI) to predict the rheological and magneto-mechanical behavior of MR materials, model complex device responses, and optimize material composition and processing conditions. AI applications in MR systems range from estimating shear stress, viscosity, and storage/loss moduli to analyzing nonlinear hysteresis, magnetostriction, and mixed-mode loading behavior. These data-driven approaches offer powerful new capabilities for material design and performance optimization, helping overcome long-standing limitations in conventional modeling techniques. Despite significant progress in MR foams, several challenges remain to be addressed, including achieving uniform particle dispersion, enhancing viscoelastic performance (storage modulus and MR effect), and improving durability under cyclic loading. Addressing these issues is essential for unlocking the full potential of MR foams in demanding applications where consistent performance, mechanical reliability, and long-term stability are crucial for safety, effectiveness, and operational longevity. By bridging experimental methods, theoretical modeling, and AI-driven design, this work identifies pathways toward enhancing the functionality and reliability of MR foams for applications in vibration damping, energy harvesting, biomedical devices, and soft robotics. Full article

Traditional magnetorheological elastomers (MREs) often suffer from limited modulus tunability and insufficient energy dissipation, which restrict their applications. This study prepared a novel composite material by an MR gel (MRG) embedded within the MRE, called the MRE encapsulating MRG, to synergistically enhance these properties. Annular and radial MRE encapsulating MRG configurations were fabricated using 3D-printed molds, and their dynamic mechanical performance was characterized under varying magnetic fields (0–1 T) via a rheometer. The results revealed that the composite materials demonstrated significantly improved magnetic-induced modulus and magnetorheological (MR) effects compared to conventional MREs. Specifically, the annular MRE encapsulating MRG exhibited a 238.47% increase in the MR effect and a 51.35% enhancement in the magnetic-induced modulus compared to traditional MREs. Correspondingly, the radial configuration showed respective improvements of 168.19% and 27.03%. Furthermore, both the annular and radial composites displayed superior energy dissipation capabilities, with loss factors 2.68 and 2.03 times greater than those of pure MREs, respectively. Dynamic response tests indicated that composite materials, particularly the annular MRE encapsulating MRG, achieve faster response times. These advancements highlight the composite’s potential for high-precision damping systems, vibration isolation, and adaptive control applications. Full article

The stochastic fluctuation characteristics of wind speed can significantly affect the control performance of train suspension systems. To enhance the running quality of trains in non-stationary wind fields, this paper proposes a semi-active control method for trains based on fuzzy rules of non-stationary wind fields. Firstly, a dynamic model of the train and suspension system was established based on the CRH2 (China Railway High-Speed 2) high-speed train and magnetorheological dampers. Then, using frequency–time transformation technology, the non-stationary wind load excitation and train response patterns under 36 common operating conditions were calculated. Finally, by analyzing the response patterns of the train under different operating conditions, a comprehensive control rule table for the semi-active suspension system of the train under non-stationary wind fields was established, and a fuzzy controller suitable for non-stationary wind fields was designed. To verify the effectiveness of the proposed method, the running smoothness of the train was analyzed using a train-semi-active suspension system co-simulation model based on real wind speed data from the Lanzhou–Xinjiang railway line. The results demonstrate that the proposed method significantly improves the running quality of the train. Specifically, when the wind speed reaches 20 m/s and the train speed reaches 200 km/h, the lateral Sperling index is increased by 46.4% compared to the optimal standard index, and the vertical Sperling index is increased by 71.6% compared to the optimal standard index. Full article

316L stainless steel slender tubes with smooth inner surfaces play an important role in fields such as aerospace and medical testing. In order to solve the challenge of difficult machining of their inner surfaces, this paper introduces a novel rotary magnetorheological finishing (RMRF) method specifically designed for processing the inner surfaces of slender tubes. This method does not require frequent replacement of the polishing medium during the processing, which helps to simplify the processing technology. By combining the rotational motion of a magnetic field with the linear reciprocating movement of the workpiece, uniform material removal on the inner surfaces of 316L stainless steel tubes was achieved. Initially, a finite element model coupling the magnetic and flow fields was developed to investigate the flow behavior of the MPF under a rotating magnetic field, to examine the theoretical feasibility of the proposed polishing principle. Subsequently, experimental validation was performed using a custom-designed polishing apparatus. Through processing experiments, with surface quality designated as the index, the influences of key parameters such as the volume content and sizes of carbonyl iron particles and abrasive particles in the MPF were comprehensively evaluated, and the composition and ratio of the MPF were optimized. Based on the optimized formulation, the optimal processing time was established, reducing the inner surface roughness from an initial Sa of approximately 320 nm to 28 nm, and effectively eliminating the original defects. Full article

Magnetorheological finishing is widely used in the high-precision processing of optical components, but due to the influence of multi-source system errors, the convergence of single-pass magnetorheological finishing (MRF) is limited. Although iterative processing can improve the surface accuracy, repeated tool paths tend to deteriorate mid-spatial frequency textures, and for complex surfaces such as aspheres, traditional manual alignment is time-consuming and lacks repeatability, significantly restricting the processing efficiency. To address these issues, firstly, this study systematically analyzes the effect of six-degree-of-freedom positioning errors on convergence behavior, establishes a positioning error-normal contour error transmission model, and obtains a workpiece positioning error tolerance threshold that ensures that the relative convergence ratio is not less than 80%. Further, based on these thresholds, a hybrid self-positioning method combining machine vision and a probing module is proposed. A composite data acquisition method using both a camera and probe is designed, and a stepwise global optimization model is constructed by integrating a synchronous iterative localization algorithm with the Non-dominated Sorting Genetic Algorithm II (NSGA-II). The experimental results show that, compared with the traditional alignment, the proposed method improves the convergence ratio of flat workpieces by 41.9% and reduces the alignment time by 66.7%. For the curved workpiece, the convergence ratio is improved by 25.7%, with an 80% reduction in the alignment time. The proposed method offers both theoretical and practical support for high-precision, high-efficiency MRF and intelligent optical manufacturing. Full article

The automotive market is looking for innovative braking solutions that can mitigate or eliminate secondary emissions. For this reason, new braking paradigms have been developed, and magnetorheological brakes could be considered a suitable solution due to their performance and controllability features. Reliability is a key factor for automotive braking systems, so it is essential to analyze the behavior of such technological solutions in iterative cycles to understand their capability of maintaining brake performance throughout their operative lifecycles. This article presents a preliminary experimental durability analysis and defines the testing standard procedures to be used as boundaries for this analysis. Then, a durability test bench is developed and produced to evaluate the magnetorheological fluid over an equivalent distance of 100,000 km. After the tests, the fluid’s characteristics are compared to its original features using a rheometer apparatus and Scanning Electron Microscopy (SEM). Full article