Kruti Shah

A low sedimentation magnetorheological fluid based on plate-like iron particles, and verification using a damper test

This study presents a new kind of low sedimentation magnetorheological fluid (MRF). Its salient properties are evaluated using a small-sized damper. The proposed MRF is characterized to investigate the effect of plate-like iron particles on rheological properties such as yield stress and flow behavior. Plate-like micron size iron particles play an important role in improving stability against rapid sedimentation as well as in enhancing the value of the yield stress. This study also considers a bidisperse MRF because this can produce a higher yield stress compared with a monodisperse suspension. Since the field-dependent yield stress is the key factor in mechanical applications, the physical properties of the MRF proposed in this work are evaluated and applied to the design of a small-sized damper which can be used for vibration control in washing machines. In order to verify the smaller effect on the damping force due to the particle sedimentation, the field-dependent damping forces are measured under two different operating conditions; one is just after filling the MRF and another after operating for 48 h. The proposed MRF is shown to be very effective in reducing adverse effects due to particle sedimentation.

Design of a new adaptive fuzzy controller and its implementation for the damping force control of a magnetorheological damper

This paper presents a new adaptive fuzzy controller and its implementation for the damping force control of a magnetorheological (MR) fluid damper in order to validate the effectiveness of the control performance. An interval type 2 fuzzy model is built, and then combined with modified adaptive control to achieve the desired damping force. In the formulation of the new adaptive controller, an enhanced iterative algorithm is integrated with the fuzzy model to decrease the time of calculation (D Wu 2013 IEEE Trans. Fuzzy Syst. 21 80–99) and the control algorithm is synthesized based on the tracking technique. In addition, for the verification of good control performance of the proposed controller, a cylindrical MR damper which can be applied to the vibration control of a washing machine is designed and manufactured. For the operating fluid, a recently developed plate-like particle-based MR fluid is used instead of a conventional MR fluid featuring spherical particles. To highlight the control performance of the proposed controller, two existing adaptive fuzzy control algorithms proposed by other researchers are adopted and altered for a comparative study. It is demonstrated from both simulation and experiment that the proposed new adaptive controller shows better performance of damping force control in terms of response time and tracking accuracy than the existing approaches.

Plate-like iron particles based bidisperse magnetorheological fluid

Magnetorheological (MR) properties are experimentally investigated for bi-dispersion suspension of plate-like iron magnetic particles dispersed in carrier liquid to see the influence of small size particle on large size MR fluid. As a first step, structural, magnetic, and morphology of two different micron size magnetic particles are described in details. The three different weight fractions of MR fluid samples are then prepared, followed by measuring their magneto-viscous and visco-elastic properties. In the steady-state shear, the Bingham yield stress obtained by extrapolating the shear stress to the zero shear rate increases by augmenting the weight fraction of small micron size magnetic particles and the strength of magnetic field. In the oscillatory strain sweep test at an angular frequency of 10 rad s−1, a transition from visco-elastic solid to visco-elastic liquid is observed and a strong chain formation is proposed to explain the mechanism for transition. The storage modulus also increases with in...

Rheological properties of soft magnetic flake shaped iron particle based magnetorheological fluid in dynamic mode

In this work, the effect of particle shape (flakes) on the magnetorheological (MR) properties of an iron based MR fluid, constituted of two different volume fractions of particles dispersed in a liquid carrier, is studied. To compare the MR effect, spherical iron carbonyl particle based MR fluid is studied. In both MR fluids, linear viscoelastic behavior has been extensively investigated using small amplitude oscillatory analysis and magnetic sweep tests, in the presence and absence of a magnetic field (H). The amplitude sweep tests reveal that flake-based MR fluid shows a higher storage modulus compared to sphere-based MR fluid and saturates at a lower magnetic field strength. The variation of storage modulus with magnetic field strength shows an Hn dependence, where n varies from 2.2 to 2.4 for 20% volume fraction while it varies from 1.6 to 2 for a dilute sample. In the case of sphere-based MR fluid, at 20% volume fraction the variation of storage modulus is nearly linear with the magnetic field at low strain amplitude, and with increasing strain amplitude shows H2 dependence. At lower volume fraction in both cases, the loss modulus increases linearly with the magnetic field strength. The observed enhancement in the MR effect in the flake-based MR fluid is likely due to the stronger particle–particle interaction which results in higher friction between the particles. The sedimentation rate decreases by nearly 50% when flakes are used. The study reveals that one can use the irregular shaped particles for MR applications at low fields (~80 kA m−1).

Rheological properties of bi-dispersed magnetorheological fluids based on plate-like iron particles with application to a small-sized damper

In this study, the rheological properties and an application of bi-dispersed magnetorheological fluid (MRF) based on plate-like iron particles are experimentally investigated. A bi-dispersed MR Fluid is prepared using two different micron-scale sizes of plate-like iron particles. In the absence of a magnetic field, the properties of the fluid are isotropic. Upon the application of a magnetic field, the magnetized particles form a chain aligned in the direction of the field, which promotes the appearance of a yield stress. The reversible transition from solid to liquid is the basic requirement of MR applications. Due to the anisotropy in the shape and formation of a less compact structure in the iron plate-like particles, weak sedimentation and good redispersibility of the proposed MR fluid are created. The physical properties of the proposed MR fluids are evaluated and applied to the design of a small-sized controllable MR vibration damper, which can be used for vibration control of a washing machine. The...

The influence of particle size on the rheological properties of plate-like iron particle based magnetorheological fluids

This work is devoted to the dependence of particle size on magnetorheological properties of magnetorheological fluid (MRF) consisting of plate-like iron particles suspended in a carrier liquid with two aspects. One aspect is to study the influence of the particle size on the rheological properties of the MRF, and the other is to investigate the influence of small-sized particles on the large-sized MRF. In order to achieve this goal, firstly, two different types of MR suspensions have been constituted by a plate-like iron particle; one is small with an average particle size of 2 μm in diameter, and the other is large with an average particle size of 19 μm in diameter. In this work, these are denoted as S-MRF and L-MRF, respectively. Secondly, in order to check the influence of the small particle size of the large-sized MR fluid, three different weight fractions of bidisperse MRF samples are prepared. The structural and morphology of plate-like iron particles are described in detail. The magnetic properties of these MR fluids are carried out at room temperature using the magnetometer, followed by the investigation on the field-dependent rheological properties of these MR fluids. It is observed that in both the S-MRF and L-MRF, the yield stress and viscosity is increased by the increasing particle size, which directly shows a correlation with the fluid magnetization. It is also identified from the test of the bidisperse MRF samples that the yield and viscosity depend on the weight fraction due to the magnetostatic interaction between the two different sizes of particles. Based on the rheological properties, some figures of merit are derived for the proposed MRF samples, which are important in the design of the application device. The sedimentation experiments for MRF samples are performed to check the stability of the MRF each day. With the basic rheological properties and sedimentation experiments, it is clearly demonstrated that the bidisperse MR suspension with a precise weight fraction has high yield stress and low sedimentation stability, which shows practical feasibility.

Damping Force Tracking Control of MR Damper System Using a New Direct Adaptive Fuzzy Controller

This paper presents a new direct adaptive fuzzy controller and its effectiveness is verified by investigating the damping force tracking control of magnetorheological (MR) fluid based damper (MR damper in short) system. In the formulation of the proposed controller, a model of interval type 2 fuzzy controller is combined with the direct adaptive control to achieve high performance in vibration control. In addition, (H infinity) tracking technique is used in building a model of the direct adaptive fuzzy controller in which an enhanced iterative algorithm is combined with the fuzzy model. After establishing a closed-loop control structure to achieve high control performance, a cylindrical MR damper is adopted and damping force tracking results are obtained and discussed. In addition, in order to demonstrate the effectiveness of the proposed control strategy, two existing controllers are modified and tested for comparative work. It has been demonstrated from simulation and experiment that the proposed control scheme provides much better control performance in terms of damping force tracking error. This leads to excellent vibration control performance of the semiactive MR damper system associated with the proposed controller.

A new magnetorheological mount featured by changeable damping gaps using a moved-plate valve structure

In this work, a new type of a magnetorheological (MR) fluid mount is proposed and its performances are experimentally investigated. The design of this MR mount is based on two operating modes of MR fluid: flow mode and shear mode. These modes are applied to the mechanism design consisting of two components: a fixed plate for applying the flow mode, and a moved plate for applying the shear mode of MR fluid motion. These plates belong to the valve-type structure of MR mount. The primary objective using the moved plate is to overcome the block-up phenomenon which frequently occurs in the conventional-type MR mount, in which there is no flow of MR fluid through the damping gap. In this research, a laboratorial fluid (MRF140) is used in the design and optimization of MR mount. This fluid features plate-like particles unlike the sphere particles. The yield stress of the fluid is measured as a function of the magnetic field and the theoretical analysis for the mount design is undertaken using the properties of the MR fluid, followed by design optimization. The objective function is concentrated on maximal damping force of the MR mount subjected to parameter constraints. Based on the results of optimization, the proposed MR mount is manufactured and tested for the performance evaluation. Vibration control capability and block-up phenomenon are investigated and compared between the proposed and conventional MR mounts.

A new resonant based measurement method for squeeze mode yield stress of magnetorheological fluids

A new approach to measure the field-dependent yield stress of magnetorheological (MR) fluids in squeeze mode using the resonance concept is proposed. The measurement system is designed using the piezolaminated cantilever beam coupled with an electromagnetic coil based MR fluid squeezing setup. The cantilever beam is maintained at resonance using simple closed-loop electronics. The magnetic field produced by the coil changes the viscosity of MR fluids and produces an additional stiffness to the resonating cantilever beam. The shift in resonant frequency due to the change in viscosity of the MR fluid is measured, and the shift in frequency is analytically related to the yield stress. Two types of MR fluids based on sphere and plate iron particles are used to demonstrate the effectiveness of the proposed measurement system.

Rheological properties of magnetorheological polishing fluid featuring plate-like iron particles

In this work, magnetorheological polishing fluid (MRP) rheological properties are experimentally investigated for bi-disperse suspension of plate-like iron particles and non-magnetic abrasive particles dispersed in carrier fluid to see the influence of small-sized non-magnetic particle on the large-size Mr fluid. As a first step, structural and morphology of iron plate-like particles are described in details. The rheological properties are then characterized using magnetorheometer. Particle size and volume fraction of both particles play an important role during the breaking and reforming the structure under application of magnetic field which influence on the rheological properties of MRP fluid. Three different constitutive models, such as the Bingham, Herschel-Bulkley and Casson equations are considered to evaluate their predictive capability of apparent viscosity of proposed MRP fluid. The yield stress increases with increasing magnetic field strength. The results obtained from three models show that the flow index exhibits shear thinning behavior of fluid. A comparative work between the model results and experimental results is also undertaken.