Showing papers on "Magnetorheological fluid published in 2021"

An explicit dissipative model for isotropic hard magnetorheological elastomers

Abstract: Hard magnetorheological elastomers ( h -MREs) are essentially two phase composites comprising permanently magnetizable metallic inclusions suspended in a soft elastomeric matrix. This work provides a thermodynamically consistent, microstructurally-guided modeling framework for isotropic, incompressible h -MREs. Energy dissipates in such hard-magnetic composites primarily via ferromagnetic hysteresis in the underlying hard-magnetic particles. The proposed constitutive model is thus developed following the generalized standard materials framework, which necessitates suitable definitions of the energy density and the dissipation potential. Moreover, the proposed model is designed to recover several well-known homogenization results (and bounds) in the purely mechanical and purely magnetic limiting cases. The magneto–mechanical coupling response of the model, in turn, is calibrated with the aid of numerical homogenization estimates under symmetric cyclic loading. The performance of the model is then probed against several other numerical homogenization estimates considering various magneto–mechanical loading paths other than the calibration loading path. Very good agreement between the macroscopic model and the numerical homogenization estimates is observed, especially for stiff to moderately-soft matrix materials. An important outcome of the numerical simulations is the independence of the current magnetization to the stretch part of the deformation gradient. This is taken into account in the model by considering an only rotation-dependent remanent magnetic field as an internal variable. We further show that there is no need for an additional mechanical internal variable. Finally, the model is employed to solve macroscopic boundary value problems involving slender h -MRE structures and the results match excellently with experimental data from literature. Crucial differences are found between uniformly and non-uniformly pre-magnetized h -MREs in terms of their pre-magnetization and the associated self-fields.

New experimental insights into magneto-mechanical rate dependences of magnetorheological elastomers

Abstract: Magnetorheological elastomers (MREs), consisting of an elastomeric matrix filled with magnetic particles, are one of the most promising multifunctional composites. The main advantage of these materials is their response to external magnetic fields by mechanically deforming and/or changing their magnetorheological properties. This multi-physical nature makes them ideal candidates for timely applications in soft robotics and bioengineering. Although several works have addressed the magneto-mechanical coupling in these composites from both experimental and modelling approaches, there is still a big gap of knowledge preventing the full understanding of their underlying physics. In this regard, there is no experimental work addressing a comprehensive magneto-mechanical characterisation combining different MRE configurations, mechanical deformation modes and magnetic conditions. Furthermore, the interplays of rate dependences into such magnetorheological behaviour still remain elusive. In this work, we provide an unprecedented experimental characterisation of a soft MRE considering more than 100 different experimental conditions involving more than 600 tests. The experiments include monotonous uniaxial compression at different deformation rates and magnetic conditions, magneto-mechanical DMA tests, relaxation tests, oscillatory shear tests at different deformation rates and magnetic conditions, magneto-mechanical shear frequency sweep tests, and novel magneto-mechanical experiments. The results obtained in this work provide full characterisation of soft MREs with a special focus on rate dependences, forming the basis to explain novel multifunctional mechanisms identified behind their coupled response. In addition, it opens the door to new constitutive and modelling approaches.

A Review on Structural Configurations of Magnetorheological Fluid Based Devices Reported in 2018-2020

Abstract: Magnetorheological (MR) fluid is a kind of smart materials with rheological behavior change by means of external magnetic field application, which has been widely adopted in many complex systems of different technical fields. In this work, the state-of-the-art MR fluid-based devices are reviewed according to structural configurations reported from 2018 to 2020. Based on the rheological characteristic, MR fluid has a variety of operational modes, such as flow mode, shear mode, squeeze mode and pinch mode, and plays unique advantages in some special practical applications. Thus, referring to these operational modes, improved engineering mechanical devices with MR fluid are summarized including brakes, clutch, damper and mount proposed over the last three years. Furthermore, some new medical devices used MR fluid are also investigated, for instance, surgical assistive devices and artificial limb. In particular, some outstanding advances on structural innovations and application superiority of these devices are introduced in detail. Finally, an overview of the significant issues occurred in the MR fluid-based devices is reported, and the developing trends are discussed for the devices with MR fluid.

The Dynamic Models, Control Strategies and Applications for Magnetorheological Damping Systems: A Systematic Review

Abstract: The magnetorheological (MR) damping devices have attracted an increasing amount of attention in the field of vibration control for their excellent performance of the vibration absorption. Systematically, the constitutive mechanical models of the MR fluids affect the control accuracy for the control strategies and the applications of the MR dampers. This work elaborately gives a systematic review on the control issues with the MR devices, thus, covering the dynamic models of the MR dampers, the state-of-the-art research, and the damping control strategies and its applications, which provide the necessary fundamental theories and the references for the damping control design of an MR damping device. According to the advanced degree of the control algorithms that are discussed in detail, they can be classified into three categories, namely, the classical control algorithms, the advanced control algorithms, and the intelligent control algorithms. The damping control strategies determine the control quality, which is the soul of an MR damping control system. There is still room to improve the algorithm for the controller for MR dampers. Employing the smart algorithms of machine learning, the work directs much more attention to the foundational research on the application of the artificial intelligence algorithms in damping control, outlining a perspective to combine the advantages of the individual different intelligent algorithms that could be an alternative solution to control of an MR damping device for the complex problems.

An overview of magnetorheological polishing fluid applied in nano-finishing of components:

Abstract: Surface quality is the most crucial factor affecting the product lifespan and performance of any component. Most earlier technologies display accuracy in the micrometre or submicrometre range, surf...

Magnetorheological elastomers — An underestimated class of soft actuator materials

Abstract: In this paper, the results of various investigations on the viscoelastic and magnetic properties of magnetorheological elastomers (MRE) in magnetic fields of variable strength, are reported. These ...

Accurate and fast estimation for field-dependent nonlinear damping force of meandering valve-based magnetorheological damper using extreme learning machine method

Abstract: The application of artificial neural network (ANN) models in magnetorheological (MR) damper has gained interest in various studies because of the high accuracy in predicting the damping force, especially for control purposes. However, the existing neural network models have apparent drawbacks such as relatively long training time and the possibility to be trapped in local solutions. Therefore, this paper aims to propose a new method to deal with a highly nonlinear behavior of MR damper using an extreme learning machine (ELM) method. The ELM method is applied to a meandering valve-based MR damper for damping force prediction, which has been recently developed. A simulation scheme is selected with damping force as the output, and current, velocity, and displacement as the inputs. The simulations are then carried out based on fatigue dynamic tests data in various frequencies and currents. The training times for more than nineteen thousand data points using the ELM method with 10, 100, 1000 hidden neuron numbers are less than 1.70 s, which is faster than the conventional ANN. Based on 50 times training processes, the ELM and ANN models have comparable average accuracies with R2 values of more than 0.95. ELM also has shown less value R2 standard deviation showing its advantage to reduce the possibility of being trapped in local solution compared to the conventional ANN.

Magnetorheological Fluid Haptic Shoes for Walking in VR

Abstract: In this article, present RealWalk, a pair of haptic shoes for HMD-based VR, designed to create realistic sensations of ground surface deformation, and texture using Magnetorheological fluid (MR fluid) RealWalk offers a novel interaction scheme through the physical interaction between the shoes, and the ground surfaces while walking in VR Each shoe consists of two MR fluid actuators, an insole pressure sensor, and a foot position tracker The MR fluid actuators are designed in the form of multi-stacked disc structure with a long flow path to maximize the flow resistance With changing the magnetic field intensity in MR fluid actuators based on the ground material in the virtual scene, the viscosity of MR fluid is changed accordingly When a user steps on the ground with the shoes, the two MR fluid actuators are pressed down, creating a variety of ground material deformation such as snow, mud, and dry sand We built an interactive VR application, and compared RealWalk with vibrotactile-based haptic shoes in four different VR scenes: grass, sand, mud, and snow We report that, compared to vibrotactile-haptic shoes, RealWalk provides higher ratings in all scenes for discrimination, realism, and satisfaction We also report qualitative user feedback for their experiences

Material removal characteristics of magnetic-field enhanced shear thickening polishing technology

Abstract: To achieve the efficient and high-quality machining of hard and brittle ceramics used in various industries, in addition to other materials that are difficult to process, a magnetic-field enhanced shear thickening polishing technology was developed in this study. Based on the coupling effect of the magnetization enhancement and shear thickening, the proposed processing technology can improve the rheological properties of the shear thickening fluid, thus realizing an adaptive and efficient removal of microscopic materials. Herein, the microscopic material removal mechanism of this technology was analysed and the rheological properties of a magnetic shear thickening polishing fluid were studied. Based on the Preston's equation, the dynamic pressure of non-Newtonian fluids and the magnetorheological polishing theory, a material removal rate prediction model was established and it had a maximum relative error of 7.56%. The influences of the polishing head rotational speed, abrasive particle concentration and carbonyl iron powder particle concentration on the material removal function were investigated and the stability of the prediction model was verified. After polishing a zirconia workpiece for 20 min, a low-damage machining surface was obtained and the surface roughness was 8.3 nm. Therefore, the effectiveness of the material removal prediction model was verified and the findings of this study provide a theoretical basis for the realization of deterministic polishing. Moreover, the feasibility of the magnetic-field enhanced shear thickening polishing method for the ultra-precision machining of hard-to-machine materials, such as hard and brittle ceramics, was verified.

Magnetic Polymer Composite Particles: Design and Magnetorheology.

Abstract: As a family of smart functional hybrid materials, magnetic polymer composite particles have attracted considerable attention owing to their outstanding magnetism, dispersion stability, and fine biocompatibility. This review covers their magnetorheological properties, namely, flow curve, yield stress, and viscoelastic behavior, along with their synthesis. Preparation methods and characteristics of different types of magnetic composite particles are presented. Apart from the research progress in magnetic polymer composite synthesis, we also discuss prospects of this promising research field.

Effect of process parameters on machinability, hemocompatibility and surface integrity of SS 316L using R-MRAFF

Abstract: Surface finish at nanometric scale is imperative for biomedical implants made up of stainless steel 316L (SS 316L) and titanium alloy to ensure the biocompatibility. However, such fine finishing is quite difficult to process. A rotational magnetorheological abrasive flow finishing process is used for nano-finishing. Rotational magnetorheological abrasive flow finishing (R-MRAFF) is one of the processes to achieve nano-level finishing. In this present study, a rotating die has been developed to perform the R-MRAFF processes with four rectangular-shaped permanent magnets held at an angle of 90° to one another. A new method for producing a variable magnetic field was investigated in this study by increasing or decreasing the distance between permanent magnets in the rotating die and workpiece fixtures. The increase in the distance between permanent magnets in rotating die and workpiece fixture leads to a decline in the value of material removal rate (MRR) as well as a percentage reduction in surface roughness (%ΔRa). This validates the importance of magnetic field intensity in the R-MRAFF process. A central composite design (CCD) in the response surface methodology (RSM) is employed to study the effect of process parameters on the response variables. The effect of the process parameter was evidenced with the help of the ANOVA technique. Optimization was carried out with constraints of maximizing both output response variables, the optimum MRR and %ΔRa, which were found as 2.02 mg/s and 50.66%. To quantify the effect of surface roughness on hemocompatibility, a platelet adhesion study was investigated. The platelet adhered area starts to decrease with the reduction in the surface roughness from 319 to 167 nm.

Novel active magnetorheological knee prosthesis presents low energy consumption during ground walking

Abstract: This study analyses the energy consumption of an active magnetorheological knee (AMRK) actuator that was designed for transfemoral prostheses. The system was developed as an operational motor unit ...

Adaptive Backstepping Control Design for Semi-Active Suspension of Half-Vehicle With Magnetorheological Damper

Abstract: This paper investigates the problem of controlling half-vehicle semi-active suspension system involving a magnetorheological (MR) damper. This features a hysteretic behavior that is presently captured through the nonlinear Bouc-Wen model. The control objective is to regulate well the heave and the pitch motions of the chassis despite the road irregularities. The difficulty of the control problem lies in the nonlinearity of the system model, the uncertainty of some of its parameters, and the inaccessibility to measurements of the hysteresis internal state variables. Using Lyapunov control design tools, we design two observers to get online estimates of the hysteresis internal states and a stabilizing adaptive state-feedback regulator. The whole adaptive controller is formally shown to meet the desired control objectives. This theoretical result is confirmed by several simulations demonstrating the supremacy of the latter compared to the skyhook control and passive suspension.

Modified crow search algorithm–based fuzzy control of adjacent buildings connected by magnetorheological dampers considering soil–structure interaction:

Abstract: Finding effective means of protecting structures from dynamic hazards is a challenging task and has gained increasing significance. As for the seismically excited adjacent structures, an intelligen...

Bifurcation of magnetorheological film–substrate elastomers subjected to biaxial pre-compression and transverse magnetic fields

Abstract: This work investigates the primary sinusoidal bifurcation wrinkling response of single- and multi-layered magnetorheological elastomer (MRE) film–substrate systems subjected to combined transverse applied magnetic fields and in-plane biaxial pre-compression. A recently proposed continuum model that includes the volume fraction of soft-magnetic particles is employed to analyze the effect of the magnetic properties upon the bifurcation response of the system. The analysis is built in a highly versatile manner using a finite-element discretization approach along the direction of the applied magnetic field and Fourier expansions along the infinite in-plane layer directions. This allows for a seamless investigation of various multi-layered structures. First, we analyze the effect of biaxial pre-compression upon the critical magnetic field for a film–substrate system and for various mechanical stiffness ratios. We observe a kink in the critical magnetic curves and a reflection in the corresponding wave numbers as they cross the equi-biaxial pre-compression regime. Subsequently, we consider a MRE film bonded to a MRE substrate and study the effect of the particle volume fraction ratios in those two parts. As a result, we obtain sharp pattern transitions, i.e., long-to-short wavelength changes with only minor perturbations of the applied pre-compression. The presence of a magnetic substrate changes qualitatively and quantitatively the bifurcation response of the film–substrate system. Finally, we carry out a data-mining exercise to minimize the critical magnetic field at bifurcation by using three different topologies, i.e., a monolayer, a bilayer and a sandwich film. We find that the topologies resembling closely the monolayer one lead to the lowest critical magnetic fields for a given biaxial pre-compression.

Reversible and non-reversible motion of NdFeB-particles in magnetorheological elastomers:

Abstract: Magnetorheological elastomers are a class of smart hybrid material where magnetic microparticles are embedded in an elastomer matrix. The combination of elastic and magnetic properties leads to hig...

Optimized Fuzzy Skyhook Control for Semi-Active Vehicle Suspension with New Inverse Model of Magnetorheological Fluid Damper

Abstract: To improve the performance of vehicle suspension, this paper proposes a semi-active vehicle suspension with a magnetorheological fluid (MRF) damper. We designed an optimized fuzzy skyhook controller with grey wolf optimizer (GWO) algorithm base on a new neuro-inverse model of the MRF damper. Because the inverse model of the MRF damper is difficult to establish directly, the Elman neural network was applied. The novelty of this study is the application of the new inverse model for semi-active vibration control and optimization of the semi-active suspension control method. The calculation results showed that the new inverse model can accurately calculate the required control current. The fuzzy skyhook control method optimized by the grey wolf optimizer (GWO) algorithm was established based on the inverse model to control the suspension vibration. The simulation results showed that the optimized fuzzy skyhook control method can simultaneously reduce the amplitude of vertical acceleration, suspension deflection, and tire dynamic load.