Magnetorheological Fluid-Based Haptic Feedback Damper

CHARACTERIZATION OF RHEOLOGICAL PROPERTIES OF NOVEL MAGNETORHEOLOGICAL FLUIDS

Soft hybrid magnetorheological elastomer: Gap bridging between MR fluid and MR elastomer

This study proposes a model for describing magnetorheological (MR) fluid dynamic behavior. Experimental research was conducted to validate the model that represents the dynamic behavior of the MR fluid. MR fluid composed of 35 % carbonyl iron and 65 % silicon oil was used. In the experimental setup, sinusoidal excitation was applied to MR fluid under various frequencies while applying various currents, and the experimental data, including displacement, velocity, time and force, were recorded. Proposed model was described and details of the model explained. Force was predicted from the model by using computer software and approximated to experimental force. The error between the predicted results from the model and the measured data was calculated. After the experiments and optimization, the proposed model was compared with extended Bingham and viscoelastic-plastic models. After the analysis, it was seen that the proposed model coincides with other models in the literature. This novel model is practical to use in many engineering applications.

To date, several applications of magnetorheological (MR) fluids are present in the industrial world, nonetheless system requirements often needs better material properties. In technical literature a previous work shows that MR fluids exhibit a pressure dependency called squeeze strengthen effect. Since a lot of MR fluid based devices are rotary devices, this paper investigates the behaviour of MR fluids under pressure when a rotation is applied to shear the fluid. The system is designed in order to apply both the magnetic field and the pressure and follows a Design of Experiment approach. The experimental apparatus comprises a cylinder in which a piston is used both to apply the pressure and to shear the fluid. The magnetic circuit is designed to provide a nearly constant induction field in the MR fluid. The experimental apparatus measures the torque as a function of the variables considered and the yield shear stress is computed. The analysis of the results shows that there is a positive interaction between magnetic field and pressure, which enhances the MR fluid performances more than twice.

Temperature compensation in viscoelastic damper using magnetorheological effect

Magnetorheological (MR) fluids have garnered sustained attention for their reversible magneto-responsive properties, and bidisperse systems integrating micro- and nano-sized magnetic particles have emerged as a prominent research focus for optimizing comprehensive performance. However, existing research rarely systematically investigates the influence of nanoparticle micro-morphology on the synergistic regulation of MR fluid performance, and comprehensive evaluations often lack integration of thermal stability and thixotropy-key metrics for practical engineering service. To address these gaps, bidisperse MR fluids were prepared by combining micrometer-sized sodium lauryl sulfate (SDS)-modified carbonyl iron powder (mCIP) and nanoscale Fe3O4 with two distinct morphologies (octahedral and sheet-like structure). Cross-scale experimental characterizations were conducted: microscale analyses (scanning electron microscope, energy dispersive X-ray spectrometry, Fourier transform infrared spectroscopy, vibrating sample magnetometer) clarified particle microstructure, elemental composition, and magnetization properties; macroscale tests evaluated sedimentation stability (60-day observation), thermal stability (0–80 °C), thixotropy (three-interval test), zero-field viscosity (1–100 s−1), and MR effect (shear yield stress under 0–1.0 T). The results showed that SDS modification reduced mCIP agglomeration, while octahedral Fe3O4 filled mCIP gaps to form a “micron-nano” hybrid network. The optimal formulation (mCIP: octahedral Fe3O4 = 8:2) exhibited low sedimentation rate (17.24% at 60 days), favorable thermal stability and thixotropy, balanced zero-field viscosity (1.74 Pa·s @ 100 s−1), and shear yield stress (21.2 kPa @ 1.0 T). In contrast, sheet-like Fe3O4 induced stacking-induced agglomeration, worsening stability. This study provides a feasible strategy for morphology-dependent optimization of high-performance bidisperse MR fluids and supports the development of long-service-life MR devices in engineering and biomedicine.

Magnetorheological fluids (MRFs) include suspensions of ferromagnetic particles, medium oils, and several types of additives. Their rheological properties change rapidly, stably, and repeatedly when magnetic fields are applied. In this present study, we focus on a haptic device using MRFs. Though particle sedimentation is one of the drawbacks of MRFs, we developed an MRF using iron particles of size 10–100 µm and silicon oil (Nano-MRF); more specifically, we use this material as a working material for the haptic device. We developed a prototype of an MRF brake as a core device for haptic control. In this paper, we describe our design method for the corresponding magnetic circuit. In addition, we designed a detailed structure for the unit. We investigated the basic properties of this unit by using a test machine with two types of MRFs, i.e., our Nano-MRF and a commercial MRF. From our results, the Nano-MRF showed better stability and response times versus that of conventional materials.

Most magnetorheological (MR) fluid dampers are designed as fixed-pole valve mode devices, where the MR fluid is forced to flow through a magnetically active annular gap. This forced flow generates the damping force, which can be continuously regulated by controlling the strength of the applied magnetic field. Because the size of the annular gap is usually very small relative to the radii of the annulus, the flow of the MR fluid through this annulus is usually approximated by the flow of fluid through two infinitely wide parallel plates. This approximation, which is widely used in designing and modeling of MR dampers, is satisfactory for many engineering purposes. However, the model does not represent accurately the physical processes and, therefore, expressions that correctly describe the physical behavior are highly desirable. In this paper, a mathematical model based on the flow of MR fluids through an annular gap is developed. Central to the model is the solution for the flow of any fluid model with a yield stress (of which MR fluid is an example) through the annular gap inside the damper. The physical parameters of a MR damper designed and fabricated at the University of Manchester are used to evaluate the performance of the damper and to compare with the corresponding predictions of the parallel plate model. Simulation results incorporating the effects of fluid compressibility are presented, and it is shown that this model can describe the major characteristics of such a device—nonlinear, asymmetric, and hysteretic behaviors—successfully.

Experimental study on the energy absorption of porous materials filled with magneto-rheological fluid

In order to improve the environmental adaptability and interaction stability of industrial robotic arms, a flexible joint with variable damping and stiffness based on magnetorheological (MR) technology was proposed. The mechanical models for variable stiffness and damping of MR flexible joint were established, and the relationship between cam surface and variable stiffness element was derived based on the energy method. Subsequently, the variation patterns of equivalent stiffness and damping of the prototype under different excitations were experimentally tested, and the test results show that its mechanical properties meet the design requirements. To further verify the performance of the MR flexible joint on the robotic arm, we setup a collision buffering test system and investigated the buffering performance of the system under different working conditions. The buffering test results indicate that when the current of variable stiffness element is 2.0 A, the peak collision acceleration of the system after installing the MR flexible joint decreases by about 40.19% compare with the rigid collision.

In order to control the vibration of civil building structures, a magnetic rate-controlled stage damper (MRCSD) is designed based on a magnetorheological shear thickening fluid (MR-STF). The key technology and performance test of the damper and the parameter identification of the mechanical model are studied. The experimental results show that the main cylinder filled with MR-STF combines the magnetorheological (MR) effect and the shear thickening effect, which has a strong impact on energy dissipation and vibration reduction. Therefore, the designed damper is superior to the traditional viscous damper. With the increase of magnetic field strength, the shear thickening effect of the MR fluid is inhibited and the MR effect is more obvious. The MRCSD can improve the performance of vibration isolation and vibration reduction by controlling damping. Under a different intensity of earthquake, the maximum output can reach 250.2 kN; the mechanical model of the MRCSD is established; and the design parameters of the damper are determined. The theoretical results obtained from the mechanical model of the MRCSD are consistent with the experimental results, which show that the parameter identification method is feasible and effective.

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.

Influence of composition of carbonyl iron particles on dynamic mechanical properties of magnetorheological elastomers

Vibration isolation methods that vary damping and stiffness have demonstrated excellent authority over system vibration, thus, potentially making them attractive for many applications. However, conventional devices for controlling variable stiffness are typically complicated and difficult to implement in most applications. To address this issue, a new method is proposed that requires two magnetorheological (MR) fluid dampers placed in series. With this configuration, variable damping and stiffness vibration control is simultaneously achieved by varying a small current to the MR dampers. This paper presents a theoretical and experimental analysis of a two degree-of-freedom system that is controlled by the MR dampers. Five different control schemes involving the variable damping and stiffness are explored. The time and frequency responses of the two degree-of-freedom system to a random input show that combined variable damping and stiffness control provides the best vibration isolation over a frequency range spanning the system’s two structural vibration modes. The experimental results agree well with the theoretical analysis.

Mechanical properties of magnetorheological (MR) fluids are classified into pre-yield and post-yield regions according to whether the shear stress is below or above the yield stress. MR fluids within the pre-yield region exhibit viscoelastic properties; and these properties are important for understanding MR suspensions, especially for vibration damping applications. MR suspensions composed of reduced iron powders dispersed in silicone oil are utilized to study the viscoelastic properties with the help of a strain-controlled rheometer with plate-plate configuration. Two types of experiments, i.e. strain-amplitude sweep mode and frequency-sweep mode, were carried out to investigate the viscoelastic properties of MR fluids: (a) strain-amplitude sweep mode, the strain amplitude was swept from 0.0001 to 0.001 at a fixed driving frequency of 10 Hz. (b) Frequency-sweep mode, the driving frequency was swept from 1 Hz to 100 Hz at a constant strain amplitude of 0.001. The results show that both storage modulus G´ and loss modulus G´´ decrease with the increment of the strain amplitude, however, the loss factor increases with the increment of the strain amplitude. On the other hand, both the storage modulus and loss modulus increase with the increment of frequency, which is different from the loss factor. Moreover, the effects of magnetic field and volume fraction on the viscoelastic properties are also investigated. The higher the magnetic field, the higher the storage modulus and loss modulus, and the lower the loss factor. The higher the volume fraction, the higher the storage modulus and the loss factor.