Magnetorheological Fluid Flow Research Articles

Viscoelastic Fluid Flow Model for Hydrodynamic Behaviour of Magnetorheological Fluid in Valve and Shear Modes for a Damper System

In this present study, the flow behaviour of magnetorheological fluid in valve and shear modes for damping system is modelled and analysed. The fluid is modelled as viscoelastic fluid flowing between two parallel plates in pressure driven flow mode, and also as direct shear mode. In the work, the post-yield shear thinning or thickening behaviour of magnetorheological fluids are accounted for. The velocity and pressure distributions in the unsteady magnetorheological fluid flow between the electrodes of the damper are obtained by solving the momentum equation of the magnetorheological fluid flow using the Laplace transform method. There is an excellent agreement between the results of the present model and the results of the experimental studies. The adopted viscoelastic flow model describes that the rheological behaviour of the fluid is separated into distinct pre-yield and post-yield regimes. The fluid flow velocity, velocity gradient, and shear stresses have all been shown to be enhanced by an increase in the pressure drop. The viscosity of the fluid increases with an increase in the volume fraction of particles in the fluid, which causes the resistance of the fluid to flow to increase and thereby, reduces the fluid flow velocity. Fluid flow velocity is decreased as a result of increasing magnetic field strength. The design of clutches, rotary brakes, dampers, shock absorbers, prosthetic devices, polishing and grinding tools, etc. will all benefit greatly from the adoption of the current model.

Multi-Physical Field Simulation of Magnetorheological Fluid Flow State in Valve Magnetorheological Damper

Magnetorheological fluid (MRF) is a kind of magnetic field responsive intelligent fluid, which is widely concerned in the field of damping and vibration reduction. The flow state of MRF plays a key role in vibration control in dampers. In this work, the flow behavior. of magnetorheological fluid (MRF) in a valve damper is studied through multi-physical field simulations. The objective is to comprehensively comprehend the influence of the magnetic field on the velocity distribution and pressure drop of the MRF within the damper channel. The magnetic field is generated by creating an electrified coil, and the magnetic flux density is subsequently changed by adjusting the current. The magnetic field calculation shows that the magnetic field is almost perpendicular to the MRF flow direction at the narrowest part of the damper channel. Next, based on the coupling calculation of multiple physical fields between fluid flow, electric field, and magnetic field, the flow velocity and pressure characteristics of MRF in the flow channel were calculated and analyzed. The results indicate that at the slit where the MRF flow direction is perpendicular to the magnetic field direction, the volume force acting on the MRF reduces its flow velocity, resulting in a significant pressure difference between the left and right sides of the flow channel. Additionally, the flow rate of MRF exhibits a decrease as the magnetic field strength increases. When the magnetic field strength increases from 0. 5T to 1. 5T, the flow rate of MRF fluid at the narrowest part of the flow channel decreases by about 0. 18m/s.

Dynamic analysis of magnetorheological damper incorporating elastic ring in coupled multi-physical fields

The elastic ring assumes a multifunctional role, crucially providing support and reshaping oil-film thickness distribution in applications such as squeeze film dampers, demonstrating its practical efficacy. In this work, a magnetorheological damper (MRD) incorporating an elastic ring is proposed for the first time to improve the performance of damper. The innovative configuration of the elastic ring magnetorheological damper (ERMRD) is fabricated and integrated into a test platform of rotor system. The multi-filed coupling dynamic model of ERMRD is developed involving magnetic field interactions governed by Kirchhoff law, magnetorheological fluid flow dynamics derived from lubrication theory, and the elastic ring deformation based on thin plate theory. The intricate influence mechanisms of elastic ring and excitation current on oil-film characteristic of ERMRD, encompassing oil-film pressure, oil-film force, oil-film stiffness and damping, are investigated in detail. To substantiate the capabilities of ERMRD, it is implemented within the rotor system and a coupled dynamic model is established using Lagrange equation. This is followed by an in-depth analysis of the dynamic response using the Newmark-β method, including a comparative assessment with the conventional MRD. The results reveal that the elastic ring and excitation current influence oil-film pressure distribution in ERMRD from different perspectives, leading the oil-film force to present diverse variation characteristics. Compared to MRD, ERMRD exhibits weaker nonlinearity and superior damping performance.

Magnetohydrodynamics analysis of magnetorheological fluid damper

A key feature of magnetorheological fluid is its variability of rheological properties in which upon exposing this fluid, the viscosity of the fluid changes accordingly. Hence this nature can be implemented in various engineering applications. To understand its influence in a magnetorheological (MR) damper, it is essential to study the flow behaviour using computational and numerical methods. The main objective of this work is to estimate the influence of the external magnetic field on the fluid flow velocity inside the damper using magnetohydrodynamic analysis. Finite element analysis, magnetostatic analysis, and magnetohydrodynamic (MHD) analysis have been carried out to investigate the change in the shape of the velocity profile across the flow gap of the monotube MR damper under the various magnitude of magnetic force using the MHD module of ANSYS fluent software. The simulation is conducted by considering laminar, steady-state, and incompressible fluid flow. In finite element analysis, the magnitude of magnetic flux density (MFD) ‘B’ was evaluated at various direct currents. Later, obtained MFD has been applied perpendicular direction to the flow of MR fluid. The effective length of the fluid exposed to the MFD is taken as 2 mm to 28 mm in an overall flow length of 30 mm. The extracted results have shown that the fluid flow velocity reduces with an increase in the magnetic flux density. It has been observed that 10.42 % reduction in velocity upon increasing the magnetic flux density from 0.25 T to 1 T at 75 kPa pressure. The reason for a reduction in velocity is because of variation in the rheological properties of the fluid under the magnetic field, which is very much essential to produce a good damping effect in the MR damper.

Influence of temperature of a magnetorheological fluid on damping of vibration disturbances by hydraulic mounts

The issues of dynamic stiffness coefficient control and increasing the damping ability of magnetorheological vibration mounts (MR-hydromounts) are considered. It is shown that in order to reduce the dynamic stiffness coefficient and increase the damping ability of the MR-hydromount it is necessary to reduce the coefficient of hydraulic resistance of the working magnetorheological fluid flow, which can only be achieved by increasing the number of throttle channels in the baffle plate. Calculation of the dynamic stiffness coefficient of the MR-hydromount depending on the magnetic field strength in the magnetorheological fluid and its heating temperature is presented. Keywords: inertial transformer, magnetorheological transformer, magnetorheological fluid, hydromount, working fluid, heating temperature, dynamic stiffness coefficient. gord349@mail.ru, acidwolfvx@rambler.ru, oxulkovs@mail.ru, aplehov@mail.ru, dm_titov@list.ru

Theoretical design and experimental study of magnetic circuit for magnetorheological (MR) damper of shear-valve mode

According to the analysis of shear flow and pressure difference flow of MR fluids, the damping force of MR shear-valve damping force was analysed and calculated, and a magnetic circuit of Magnetorheological (MR) damper was designed. Based on the designed magnetic circuit, the degree of magnetic saturation and the dynamic characteristics of MR fluid damper, such as impedance, current, velocity and frequency were investigated. Magnetic induction testing of damping clearance was conducted, the test results show that when the coil current is 1.4A, the magnetic induction intensity reaches 0.55T.The bench test results show that when the piston speed is constant and the current is less than 1.36A, the variation range of damping force increases significantly. However, when the current is greater than 1.36A, the damping force tends to be stable and the coil reaches magnetic saturation, and energy indication characteristic of MR damper also show the same trend, which are consistent with the theoretical results. The results of this study can provide useful guidance for the magnetic circuit design of shear-valve MR fluid damper.

Analysis on affecting factors of the ribbon fluctuation in Array-MRF

Large aperture planar optical elements are required in high power laser systems, and the mid-spatial frequency error of the surface of the high-power laser component will affect the normal operation of the high-power laser system. In recent years, there are many new MRF devices, but these devices only improve the removal efficiency of polishing materials and ignore the stability of MRF tools. As we all know, the fluctuation of the MRF polishing ribbon will affect the stability of the removal function, which will make the surface of the processed component produce the mid-spatial frequency error. Therefore, based on the array magnetorheological pole structure newly developed in our laboratory, this paper tests its magnetic field distribution and studies the influencing factors of array magnetorheological ribbon fluctuation. Based on the magnetic field force, the effects of magnetorheological fluid flow, polishing wheel speed, and magnetic pole structure on ribbon fluctuation are analyzed. Finally, by using the improved array magnetorheological device to obtain a stable removal function, the volume removal efficiency of fused silica reaches 0.022mm3/min, which verifies the feasibility of the improved device and doubles the removal efficiency of magnetorheological finishing of a single ribbon. Therefore, we use controlled magnetorheological processing flow and speed to control ribbon fluctuations and designing the magnetic pole structure, to control the stability of magnetorheological processing.

Development of a new magnetorheological impact damper with low velocity sensitivity

The velocity sensitive characteristic of the conventional linear magnetorheological (MR) damper is undesirable in the application of impact protection. It will induce large damping forces when the damper suffers high velocity impacts, whilst comprising the energy dissipation efficiency of the damper and posing a serious threat to occupants and mechanical structures. This work reports a new MR impact damper (NMRID) with low velocity sensitivity. Unlike the conventional MR impact damper (CMRID) in which MR fluids (MRFs) flow from one chamber to the other through a small annular gap between the piston and cylinder, the NMRID has a whole annular gap between the shaft and cylinder that is filled with MRFs, and the MRFs work in a pure shear mode without any liquid flow. In this work, a NMRID and a CMRID were prototyped. The velocity sensitivities of these two impact dampers were compared via numerical analysis and experimental impact tests. The analysis and test results indicate that NMRID possesses a much lower velocity sensitivity than the CMRID; the dynamic range of the NMRID decreases less than CMRID with the increase of nominal impact velocity. Then, to demonstrate the controllability of NMRID, impact tests with a bang–bang control were implemented, and the peak force of NMRID was successfully controlled around a target force under different levels of nominal impact velocity. This research proves that the designed NMRID is less sensitive to velocity than the CMRID and the NMRID has good controllability, demonstrating that the NMRID can serve as a better candidate than CMRID in applications with high impact velocity.

Unsteady extension of quasi-steady physical modeling and experimental verification of a magnetorheological energy absorber

Magnetorheological (MR) fluids are promising in controllable damping based on regulated apparent viscosity under magnetic field control, and they are employed in various damping devices such as automotive dampers and energy absorbers for artillery or landing gears by medium substitution with structural adaptations. In this study, we designed and fabricated a magnetorheological energy absorber (MREA) with disc springs as recoiling parts, modeled the MR fluid flow based on the Bingham constitutive model, and then carried out unsteady extension based on the quasi-steady model. The experimental tests of the MREA show that the unsteady extension of the quasi-steady model can designate the behaviors of the MREA in different impact speeds better than the original; thus, the controllability of the MREA is verified. An interesting phenomenon, where a rippled MREA peak force is observed at the saturated excitation when the impact speed is not so high and disappears when the impact speed is high enough, is accounted from the viewpoint of flow modeling and finally verified by more experimental results.

Investigation of a non-Newtonian MR fluid flow between parallel plates by developed CFD code for different numerical schemes

Magnetorheological (MR) fluids are composed of a solution of micron-sized magnetizable particles dispersed in a carrier fluid, typically oil. Thus, the MR fluids are classified as smart fluids by showing variable apparent viscosity under a precisely controllable external magnetic field. This feature of the MR fluids gave the possibility to use them in the MR dampers to control variational damping forces. In this work, an MR damper on relatively small scales is considered to investigate the MR fluid flow behavior through the piston annuli where the magnetic field exists. This work mainly focuses on the numerical solutions of the flow variables in a magnetically excited non-Newtonian flow medium by comparing analytical results for various Reynolds numbers. The Herschel–Bulkley (HB) viscous model is used for the non-Newtonian characteristic of the MR fluid. For the numerical modeling of the HB viscous model, the regularized approaches are used to avoid numerical errors. However, contrary to the actual HB model, the regularized models can be incapable to give true apparent viscous values at very low shear rates depending on the regularization parameters. Thus, the present study aims to give a better understanding of choosing the optimal regularization parameters for the studied flow conditions. The second part of the study discusses the numerical discretization schemes aiming to present their performances while changing the Reynolds number between 0.002 and 1. In this manner, a Computational Fluid Mechanics (CFD) solver has been developed for two-dimensional geometries which are meshed with structured grids by using six different discretization schemes including two of the most known total variation diminishing (TVD) schemes. For simplicity of the problem, a two-dimensional parallel plates geometry and a constant magnitude of the magnetic field intensity along the piston annuli are assumed. The study also summarizes the CFD technique by evaluating the physical meaning of the flow field variables.

Research on the Flow and Transmission Performance of Magnetorheological Fluid between Two Discs

The viscoplastic flow of magnetorheological fluid in a disc was analyzed based on the Navier–Stokes Momentum Equation, and the yielded and unyielded decomposition surfaces were obtained. For the shear-thinning phenomenon of magnetorheological fluid, the magnetorheological properties of the magnetorheological fluid were described based on the Herschel–Bulkley model. Then, the relationship between torque, magnetic field, material, size and motion was established, and the magnetic field and working gap were optimized and analyzed. The results show that in the unyielding region, the magnetorheological fluid flows rigidly. In the yielding region, it flows as a viscous fluid. The degree of error of the proposed torque equation decreased gradually with the increase to current, as observed by experimental comparison.

An experimental and artificial neural network investigation on the laminar flow of magnetorheological fluids through circular pipes

Fluids can change their physical properties when they are exposed to magnetic fields. Magnetorheological (MR) fluids are classified as smart materials because their viscoelastic properties can increase by the application of the magnetic field. Accordingly, they are used in different engineering applications such as flow control and vibration damping. In this study, three different types of MR fluids flow in circular pipes with diameters of 10 and 15 mm and length of 300 mm were experimentally investigated with and without applying the magnetic field. An electromagnetic device was designed and manufactured in order to create a magnetic field induction for experiments. Throughout the experiments, the range of magnetic field induction value was B = 0–0.15 T, increased to 0.01 T. Based on the results obtained by the experimental study, it can be asserted that applying the magnetic field prompted an increase in the viscosity of MR fluids, leading to decreasing flow velocity. At B = 0.15 T, which is the highest value of the magnetic field, the flow velocity values dropped by 95%. Subsequently, the artificial neural networks algorithms are used in accordance with the obtained results to develop a correlation that clarifies the effect of the magnetic field on the flow velocity. The results show that the experimental and ANN models perform very similarly, and the ANN algorithm yields better results as a tool to predict the MR fluid flow behavior.

Research of Flow Stability of Non-Newtonian Magnetorheological Fluid Flow in the Gap between Two Cylinders

This paper deals with a mathematical modeling of flow stability of Newtonian and non-Newtonian fluids in the gap between two concentric cylinders, one of which rotates. A typical feature of the flow is the formation of a vortex flow, so-called Taylor vortices. Vortex structures are affected by the speed of the rotating cylinder and the physical properties of the fluids, i.e., viscosity and density. Analogy in terms of viscosity is assumed for non-Newtonian and magnetorheological fluids. Mathematical models of laminar, transient and turbulent flow with constant viscosity and viscosity as a function of the deformation gradient were formulated and numerically solved to analyze the stability of single-phase flow. To verify them, a physical experiment was performed for Newtonian fluids using visualizations of vortex structures—Taylor vortices. Based on the agreement of selected numerical and physical results, the experience was used for numerical simulations of non-Newtonian magnetorheological fluid flow.

Damping characteristics of a magneto-rheological damper with dual independent controllable ducts

This paper presents the damping characteristics of a linear magneto-rheological (MR) damper with dual controllable ducts based on numerical and experimental analysis. The novel MR damper consisting of a dual-rod cylinder system and a MR valve is used to reduce the influences of viscous damping force and improve dynamic range. Driven by the dual-rod cylinder system, MR fluid flows in the MR valve. The pressure drop of the MR valve with dual independent controllable ducts can be controlled by tuning the current of two independent coils. Based on the mathematical model and the finite element method, the damping characteristics of the MR damper is simulated. A prototype is designed and tested on MTS machine to evaluate its damping characteristics. The results show that the working states and damping force of the MR damper can be controlled by the two independent coils.

Numerical design of load response in magneto-rheological actuators for sheet metal stamping

Auxiliary systems for sheet forming processes are widely used to improve products accuracy and increase tools life. As example, in blanking hydraulic dampers are widely used to reduce shocks and vibrations; nitrogen springs are often integrated in deep drawing tools to correct the ram tilt or to locally increase the blank-holder force, obtaining geometrical features on the stamped blank with one press pass. In this paper, a Magneto-Rheological (MR) semi-active actuator is developed for sheet forming operations and the interaction between MR fluid and electromagnetic field is investigated by Finite Element (FE) analysis. To overcome the limitations of gas springs and hydraulic actuator, the static electromagnetic circuits is reconfigured with respect of conventional MR actuators known in the state-of-the-art. The novel MR actuator has an inner bore where the electric windings are placed, while the narrow gap, in which the active MR fluid flows, is obtained between the inner bore and the cylinder internal surface. The resulting magnetic fields H and induction fields B, as well as the selection of components materials, are studied through the magneto-static FE model. The results from FE simulations show a longer activation length along the gap resulting in higher controllable forces values, without increasing the overall dimensions of the proposed prototype.

The heat flow coupling effect of laser-assisted magnetorheological polishing

During the magnetorheological polishing process of concave workpieces, the magnetorheological fluid tends to accumulate at the entrance of the polishing zone, resulting in a decrease in the polishing efficiency and quality. To solve this problem, in this paper, laser-assisted magnetorheological polishing technology was proposed. Based on the theory of fluid mechanics and heat transfer, a three-dimensional temperature field distribution model of the spherical polishing film was established to achieve local temperature control at the entrance of the polishing zone. Then, the functional relationship between the viscosity of the magnetorheological fluid and the temperature was obtained experimentally. On this basis, the shear force and hydrodynamic pressure models of the polishing zone were established, which reveal that the heat flow coupling effect can increase temperature at the inlet of the polishing zone and reduce the viscosity of the local magnetorheological fluid, thereby reducing the shear stress in the polishing zone. The results show that when the laser power is 3 W and the magnetorheological fluid flow rate is 6 ml/s, the viscosity of the magnetorheological fluid at the entrance can be effectively reduced, and the shear force in the polishing zone decreases slightly.

Effect of the controllable support elements lubricated by magnetically sensitive fluids on chaotic and regular vibration of flexible rotors during rubbing

The proposed new rotor support element consists of a hydrodynamic bearing and a magnetorheological squeeze film damper. The damping is controlled by the change of resistance against the flow of magnetorheological fluid due to action of a magnetic field generated by electric current powering the electric coils. This paper deals with the study of the effect of the proposed support element on character of the rotor vibration during rubbing when impacts between the disc and the walls of a hole of square shape in the stationary part are induced. The system is excited by the rotor unbalance. The goal of the analysis is to investigate the effect of the applied current generating magnetic field on regularity of the rotor vibration. The results of the simulations show that the character of the vibration depends on speed of the rotor rotation and application of the current of right magnitude can change irregular oscillation into periodic and reduce magnitude of the impact forces. The proposed support element makes it possible to utilize all advantages of hydrodynamic bearings. The control of the damping effect is very simple as the damper can work only in the on/off regime. The performed study contributes to learning more on the design possibilities of suppression of undesirable phenomena induced by the rotor rubbing.

Magnetorheological valves based on Herschel–Bulkley fluid model: modelling, magnetostatic analysis and geometric optimization

Magnetorheological (MR) fluids find wide application in various engineering applications. At the design stage of any MR devices, choosing a suitable rheological model for describing the flow behaviour is very critical. Since, the Herschel–Bulkley (H–B) is the most suitable model to describe the flow behaviour of MR fluids, the present study models the flow of MR fluid in the annular valve using the H–B model and does geometric optimization of the valve for three different commercially available MR fluids. The work discussed in the paper consist of three broader parts viz. (i) flow modelling, (ii) magnetostatic analysis and (iii) geometric optimization. In flow modelling, MR fluid flow is modelled using the H–B fluid model and validated by computational fluid dynamic analysis in ANSYS environment. Further, in magnetostatic analysis, for calculating the values of objective functions during the optimization process, magnetic flux density in the MR valve has been calculated using a polynomial model for the relative magnetic permeability for three different MR fluids, rather than conventionally choosing a constant value which is valid only for low ranges of current. The magnetostatic analysis has been validated through finite element modelling in ANSYS software package for different valve geometries. After defining the magnetization model for the chosen MR fluids and geometric design of the valve, variation of valve mass and performance indices such as damping force, dynamic range, inductive time constant and control energy, have been shown for all chosen fluids. In geometric optimization, the performance indices of the valve have been kept as objective functions which incorporate H–B fluid model for its definition. Such work has not been reported in the literature. Finally, a single-objective minimization problem has been formulated for the optimization with application-specific weight factors and solved using Genetic Algorithm in MATLAB® environment. The optimal results are then discussed and the best possible MR fluid has been suggested for the chosen applications.

Design optimization of magnetorheological damper geometry using response surface method for achieving maximum yield stress

Field controllable magnetorheological (MR) damper has gained prominence as a suitable vibration control device for a wide variety of applications as they offer the combined advantages of high-performance metrics of a fully active vibration control system with the cost metrics of a passive vibration control system. The functional quantity that influences the damping performance of a magnetorheological damper is the yield stress of the magnetorheological fluid across the fluid flow gap when the magnetic field is applied. To achieve maximum damping output from the magnetorheological damper, the geometry of the damper piston needs to be optimized. The main geometrical design parameters of the damper piston are the pole width, magnetorheological fluid flow gap, distance between piston rod and coil and the outer pole thickness. The optimization of the damper geometry is carried over with magnetic field strength and yield stress as response variables in two different iterations. A quadratic polynomial function is considered for both the response variables. The yield stress response variable is found to exhibit a more accurate following through the regression equation and it is selected as the response variable of choice. The individual effect of each of the design variable and the interaction effect of the design variables over the yield stress response variable is studied in this research paper. The optimal values of the piston geometry could be used to fabricate a magnetorheological damper prototype in future study.

A quasi-static model for the pinch mode analysis of a magnetorheological fluid flow with an experimental validation

Abstract The flow behaviors of a magnetorheological fluid (MR fluid) can be divided into four operating modes: flow, shear, squeeze and pinch mode. Despite many research works on the first three modes, the study on the pinch mode is relatively few. This study proposes a new mathematical model of the pinch mode flow motion of MR fluid and its fidelity is verified through a comparison with experimental results. In order to achieve this goal, the flow configuration of the pinch mode is provided followed by the magnetic analysis to design an appropriate magnetic circuit and to obtain the relationship between the magnetic intensity and applied current. Then, a mathematical model for predicting the pinch mode flow motion is formulated based on the quasi-static flow associated with several different conditions of the flow velocity. It is shown from a comparative work between the simulation results from the proposed mathematical model and experimental test results of the pinch mode MR damper that the proposed model fairly well predicts the field-dependent damping force in a low flow volume domain.