Conventional Magnetorheological Fluids Research Articles

Structural Design and Controllability of Magnetorheological Grease Buffers under Impact Loading.

Shock loads can pose a great threat to personnel or instruments, and efficient control of the buffering process is an effective means of reducing damage from shock energy. In this paper, magneto-rheological grease was used as the internal controllable material of the buffer to address the turbulence and settling problems of conventional magneto-rheological fluid. A bending and folding back magnetic circuit is proposed, and the magnetic circuit simulation was verified. The corresponding dynamic mechanical model was established, and the mechanical response characteristics of the buffer under impact load were also simulated dynamically. The mechanical properties of the designed and processed device were tested, and a variable current control method was used to improve the performance of the shock resistance of the buffer. The response of the magnetorheological grease buffer under different drop hammer impacts was investigated. The buffering effect and controllability of the buffer were analyzed by comparing the acceleration, velocity, and top-end cap displacement at the same drop hammer height for different current magnitudes. The results show that the buffer performance of the buffer gradually improved as the current increased. The response time of the designed new magnetorheological buffer was determined by the jump time of the peak damping force to be 9 ms. Lastly, the controllability was verified by manually and automatically adjusting the current magnitude, and the results were compared with those at 300 mm drop hammer height and 0.5 A current magnitude, and the continuous variable current control was found to be effective. This provides a feasible reference for scholars to study optimal buffer control.

Synthesis and rheological characteristics of high viscosity linear polysiloxane carrier fluid-based magnetorheological fluids

This study addresses the synthesis and field-dependent rheological characteristics of novel magnetorheological fluids (MRFs) using high viscosity linear polysiloxanes (HVLPs) as a carrier fluid. First of all, the components and preparation of novel HVLP-based MRFs (HVLP MRFs) were explained in detail and the microscopic images of each component were taken by using scanning electron microscope (SEM). Four HVLP MRF samples with different particle volume fractions of 10, 15, 20, and 26 vol% in the same HVLP carrier fluid viscosity of 800 Pa·s were synthesized to investigate the particle concentration effect on their field-dependent rheological properties. In order to understand the effect of the carrier fluid viscosity, two more HVLP MRF samples with different HVLP viscosities of 140 and 440 Pa·s in the same particle concentration of 26 vol% were also fabricated. In addition, the temperature effect on HVLP MRFs was studied by using the sample with 26 vol% in particle concentration and 140 Pa·s in HVLP viscosity under different operating temperatures of 25 °C, 40 °C, 55 °C and 70 °C. The flow curve measurements of shear stress versus shear rate in the magnetic fields were conducted by using controlled shear rate (CSR) test method with a commercial parallel-plate type rotational rheometer. From the flow curves, the field-dependent rheological properties of HVLP MRFs including static and dynamic yield stresses and the dynamic range (ratio of field on to field off yield stress) were obtained. These material characteristics were then examined as a function of varying particle concentration, varying carrier fluid viscosity, and varying temperature. A conventional commercial MRF (i.e. Lord MRF-126CD) was adopted for comparison study and its rheological properties under different temperatures were also measured and compared with those of HVLP MRFs. Using HVLP carrier fluids, it was demonstrated that the HVLP MRFs exhibited much greater suspension stability than the conventional commercial MRF.

Ultra-high stability and magnetic response of magnetorheological fluids based on magnetic ionic liquids and carbonyl iron fibers

A novel magnetic ionic liquid (IL) based on 1-methylethyl ether-3-butylimidazole cation and [FeCl4]− anion was synthesized for application as a carrier of magnetorheological fluids (MRFs). Stability and magnetic response of the MRFs were investigated as a function of the anion chemical structure and content of carbonyl iron fibers. The MRFs based on the magnetic ILs displayed better redispersibility, slower settling rates, and increased magnetic-induced stress compared with conventional MRFs based on oils or ILs. Furthermore, the mechanism of MRFs with good performance was investigated and proposed by molecular dynamic simulation. These results do not only confirm that the magnetic ILs are potential carriers of MRFs but also provide a new way to improve the stability and magnetic response of MRFs for various applications.

Thermal and Tribological Performance of Graphite Flake-Based Magnetorheological Fluid Under Shear Mode Clutch

Abstract In this research work, graphite flake has been used as an additive in magnetorheological (MR) fluid to improve its thermal and tribological performance. MR fluids with varying amounts of graphite flakes (0.5, 1, 2, 3, 4, and 5 wt%) are prepared to show effective thermal and tribological performance. A test rig is developed with a DC motor, torque sensor, and MR clutch operated in a shear mode to test the torque transmission. Results show the lubrication effects of graphite flakes in the MR fluid. Torque transmission is improved in on-state and off-state using graphite flakes-based MR fluid as compared with conventional MR fluid. Heating of the MR clutch is also reduced with the graphite flakes-based MR fluid. Wear marks and damages are decreased significantly with the increased amount of graphite flakes as found in surface roughness tests. Scanning electron microscopy and energy-dispersive spectroscopy are used to characterize the worn surfaces. This research provides information about the effectiveness of graphite flakes in the MR clutch to improve the device’s performance.

Shear thickening prevents slip in magnetorheological fluids

Magnetorheological (MR) fluids are smart fluids that solidify upon the application of a magnetic field by virtue of suspended magnetic particles forming chains. Here, the effect of shear thickening additives on the performance of MR fluids is explored and found to increase yield stress by 60% in fluids that have the same iron content. In order to explore the origin of this improvement, a series of flow- and oscillation-based rheology experiments were performed at various plate separations and the results were compared with a discrete dipole model of chain formation and breakage. Ultimately, conventional MR fluids, which are typically shear thinning, are found to yield at small strains that are consistent with slip failure where chains shear apart at one particle-particle joint. In contrast, shear thickening fluids reliably yield at high strain in a manner consistent with affine failure of the chain where each joint is pulled apart equally. The prevention of slip failure is attributed to the shear thickening additive locally increasing the effective viscosity as slip begins, thus preventing it from leading to yield. In addition to motivating the use of shear thickening agents broadly in MR fluids, these findings highlight the importance of additive choice in tuning rheological properties of MR fluids and the benefit of considering the microstructural and bulk behavior of the fluid simultaneously when synthesizing smart fluids.

The Synthesis of Organic Oils Blended Magnetorheological Fluids with the Field-Dependent Material Characterization.

Automation is one of the trending terminologies in the field of engineering to achieve various sensors and actuators such as the hydraulic system. Smart fluid is also one of the hot topics for researchers to develop a type of actuator in many control systems since the fluid’s rheological characteristics can be controlled or tuned by the intensity of the external stimuli. In this work, a new smart fluid of magnetorheological (MR) fluid is proposed and its field-dependent rheological characteristics are experimentally identified. An MR fluid using the carrier fluid as the blend of three different fluids, namely silicon oil, honey, and organic oil is prepared. In addition, two types of natural oils are used, sunflower oil and cottonseed oil. The samples are prepared using the blend as the carrier fluid, electrolytic iron powder coated with guar gum as the dispersed phase, and oleic acid as an additive. The quantity of oleic acid is optimized for 30% by weight of electrolytic iron powder. Two samples based on sunflower and cottonseed oil are synthesized and characterized for shear viscosity and shear stress with respect to shear rate subjected to a variable magnetic field. The blend-based MR fluid shows about 10% improvement over the sedimentation rate of silicon oil-based MR fluid as compared to that to conventional MR fluid. The cottonseed oil blend-based MR fluid performs better than sunflower-based fluid in terms of the viscosity and structure.

STUDY ON SEDIMENTATION STABILITY OF MAHUA AND SIMAROUBA OIL BASED MAGNETORHEOLOGICAL FLUIDS

Magnetorheological fluids (MRFs) are peculiar of smart fluids whose rheological properties can be efficiently controlled by varying applied magnetic field. Owing to this peculiar property, it can be utilized in industrial applications in semi-active devices such as dampers, actuators, etc. In this work, an effort has been attempted to produce MRFs using natural oils as carrier fluids and tested for potential replacement of conventional carrier fluids such as silicone oil. The MR fluids are prepared using silicone oil and two natural oil namely Mahua oil and Simarouba oil. Carbonyl iron (CI) and Electrolytic iron (EI) are used as suspended particles with lithium grease as an additive. The MRF using two natural based oil are known as Green magneto rheological fluids (GMRF). The characterization of suspended particles and carrier liquids was performed, followed by tests on sedimentation stability of prepared samples. To compare the sedimentation stability, the graphs of sedimentation ratio versus time are plotted for all MR fluids samples. It is found that the sedimentation stability of natural oils based MRFs are relatively better than silicone oil based MRFs for the same concentration of magnetic particles. There is potential of these natural oils based MRFs to replace the conventional MRFs However, other rheological properties like yield strength, flow characteristics etc. needs further investigation.

Rheological behavior of magnetic colloids in the borderline between ferrofluids and magnetorheological fluids

Magnetic colloids were formulated by dispersion of magnetic oxide spheres in water. Their rheological behavior was investigated for a wide range of particle diameters covering in detail the magnetic single-multidomain transition and therefore spanning the gap between ferrofluids and conventional magnetorheological fluids. The magnetoviscous effect (i.e., the ratio between the viscosity increment under field and the viscosity value in the absence of field) was found to reach a maximum for a critical particle size in the single-multidomain transition region. The observations were explained in terms of magnetization changes with particle size. The results obtained are applicable to any magnetic material (not only iron oxides) and therefore constitute a new route to enhance the magnetorheological effect. For very small particle sizes (in the superparamagnetic region), thermal motion plays a crucial role and the dimensionless viscosity scales with the Peclet number as expected for Brownian Hard Spheres. For larger particle sizes and λ>1, the dimensionless viscosity scales with the Mason number and closely follows the structural viscosity model under the mean magnetization approximation.

Development of a new magnetorheological fluid–based brake with multiple coils placed on the side housings

In this research, a new configuration of magnetorheological fluid–based brake with multiple coils placed on each side of the brake housing (multiple side-coil magnetorheological fluid–based brake) is proposed, optimally designed, and evaluated. With this configuration, the multiple side-coil magnetorheological fluid–based brake is expected to provide higher braking torque and more compact size than the traditional magnetorheological fluid–based brake. After a brief introduction about the development of magnetorheological fluid–based brake, the configuration of multiple side-coil magnetorheological fluid–based brake is proposed. Braking torque of the proposed magnetorheological fluid–based brake is then analyzed based on the Bingham plastic rheological model of magnetorheological fluid. The optimization of the proposed multiple side-coil magnetorheological fluid–based brake, the magnetorheological fluid–based brake with one coil placed on each side of the brake housing (single side-coil magnetorheological fluid–based brake), and the conventional magnetorheological fluid–based brake is then performed considering maximum braking torque and mass of the brakes. Based on the optimal results, advanced performance characteristics of the proposed magnetorheological fluid–based brake are figured out. In addition, experimental works are conducted to validate the performance of the proposed multiple side-coil magnetorheological fluid–based brake.

Double-gap plate–plate magnetorheology

A double-gap magnetorheological (MR) cell is designed, constructed, and validated using finite element method magnetostatics simulations, computational fluid dynamics calculations, and experimental data with Newtonian fluids and conventional MR fluids for a range of particle concentrations and external magnetic field strengths. This new cell is a generalization of the twin-gap device. It is capable of reaching very large magnetic field strengths and shear rates, avoiding normal force overload. More importantly, it is optimized for magnetic field homogeneity.

Durability test device for MR fluids with permanent magnet and V-shaped groove

Magnetorheological fluids (MRFs) are functional fluids whose viscosity changes when magnetic fields are applied. Therefore, these fluids are used in force and torque controllable devices. However, particle sedimentation is one of the drawbacks of conventional MRFs. To solve this problem, Kurimoto Co. Ltd developed a new fluid with sub-micron order Fe particles and a silicone-based solvent known as NanoMRF. The particle distributions of this material are stable over several months. However, its durability has not yet been fully discussed. Therefore, we developed new equipment to test endurance and examined the durability of the magnetorheological effect of the NanoMRF as well as a commercially available MRF. Our results show that the durability of the fluids was affected by the stability of the solvent. In particular, the durability is drastically improved when the solvent is supplemented by the peripheral sealing oil. The oxidation of particles is remarkably varied by the kind of solvent as well as the stability of the oxidation film on the surface of the particles. The energy of the collapse and reproduction of the particles was used not only to generate friction among the particles but also to decompose the solvent molecules.

Start-up rheometry of highly polydisperse magnetorheological fluids: experiments and simulations

An extensive experimental and simulation study is carried out in conventional magnetorheological fluids formulated by dispersion of mixtures of carbonyl iron particles having different sizes in Newtonian carriers. Apparent yield stress data are reported for a wide range of polydispersity indexes (PDI) from PDI = 1.63 to PDI = 3.31, which for a log-normal distribution corresponds to the standard deviation ranging from ν = 0.38 to ν = 0.76. These results demonstrate that the effect of polydispersity is negligible in this range in spite of exhibiting very different microstructures. Experimental data in the magnetic saturation regime are in quantitative good agreement with particle-level simulations under the assumption of dipolar magnetostatic forces. The insensitivity of the yield stresses to the polydispersity can be understood from the interplay between the particle cluster size distribution and the packing density of particles inside the clusters.

Effect of particle aspect ratio in magnetorheology

We investigate the influence of the aspect ratio of the dispersed particles in magnetorheology. Two systems are studied: conventional magnetorheological fluids prepared by dispersion of nickel nanowires, and inverse ferrofluids prepared by dispersion of glass fibers in a ferrofluid. In both cases the apparent yield stress is found to increase with aspect ratio in contradiction to available models in the literature. Experimental observations demonstrate that the particle volume fraction within the aggregates initially increases with increasing the aspect ratio of the dispersed particles. When the aspect ratio is further raised, a gel-like percolating structure forms inhibiting the formation of elongated clusters in the field direction.

Synthesis and Characterisation of Nano Silver Particle-based Magnetorheological Fluids for Brakes

Magnetorheological (MR) fluids can be used as brake friction materials subject to heat transfer properties of the fluids to dissipate the heat generated during braking action. The aim of this manuscript is to synthesise MR fluids having higher heat transfer properties than that of the conventional MR fluid. The coating of nano-silver-particles, having thermal conductivity more than five-times than that of iron particles used in the MR fluids, has been tried to enhance the heat dissipation rate of MR fluids. To perform feasibility study on usage of silver particles, three composition of MR fluids (without any silver particles, with 0.25 per cent weight and 0.50 per cent weight silver particles) were synthesised. The scanning electron microscopic photographs and EDX analysis of the iron particles have been presented. Shear strengths of all three different compositions of MR fluids were measured using magnetorheometer and the results have been plotted. The effect of silver particles on shear stress of MR fluids has been described. A flywheel-based MR brake experimental setup was developed to analyse the performance of synthesised MR fluids. ‘T’ type thermocouples were used to avail the temperature distribution of the fabricated MR brake. The results of temperature distribution of brakes containing three different compositions of MR fluids have been presented and compared.

Development of a linear damper working with magnetorheological shear thickening fluids

Magnetorheological shear thickening fluid is a smart material that exhibits both magnetorheological and shear thickening effects. This study focuses on the design and development of a novel magnetorheological shear thickening fluid–based linear damper. First, micron-sized carbonyl iron particles, at a 20% and 80% weight fraction, were immersed among the shear thickening fluid base and thoroughly mixed under a high shear condition to produce the magnetorheological shear thickening fluid. Then, a monotube damper with a bypass was designed and fabricated. The testing results using an MTS machine show that the influence of incorporating shear thickening fluid allows the 20% magnetorheological shear thickening fluid–filled damper to work in different dynamic loading velocities with the stiffness and damping changed, while, simultaneously, the dynamics of the damper depend on the variations in the magnetic field. The measured responses of the 20% magnetorheological shear thickening fluid–filled damper prove that the dampers have both the MR effect and shear thickening effect. In contrast, the 80% magnetorheological shear thickening fluid–filled damper behaves more like a conventional magnetorheological fluid–filled damper because its shear thickening effect is restrained and the MR effect becomes more obvious with higher iron volume.

Magnetorheology of dimorphic magnetorheological fluids based on nanofibers

We report a systematic experimental investigation on the use of nanofibers to enhance the magnetorheological (MR) effect in conventional (microsphere-based) MR fluids formulated in polyalphaolefin oil/1-octanol. Two kinds of nanofibers are employed that have very similar morphology but very different magnetic properties. On the one hand we use non-magnetic goethite nanofibers. On the other hand we employ magnetic chromium dioxide nanofibers. For appropriate concentrations the on-state relative yield stress increases up to 80% when incorporating the nanofibers in the formulation. A similar yield stress enhancement is found for both nanofibers investigated (magnetic and non-magnetic) suggesting that the main factor behind this MR enhancement is the particle shape anisotropy. The relative yield stresses obtained by partial substitution of carbonyl iron particles with nanofibers are significantly larger than those measured in previous works on MR fluids formulated by partial substitution with non-magnetic micronsized spherical particles. We also demonstrate that these dimorphic MR fluids also exhibit remarkably larger long-term sedimentation stability while keeping the same penetration and redispersibility characteristics.

Tribological behavior of ionic liquid-based magnetorheological fluids in steel and polymeric point contacts

A range of ionic liquids (ILs)-based magnetorheological (MR) fluids are formulated and their tribological properties investigated in steel–steel, polyoxymethylene–polyoxymethylene POM–POM and polydimethylsiloxane–polydimethylsiloxane PDMS–PDMS point contacts. The effect of particles in dispersion is investigated by measuring neat ILs in the same tribopairs. The boundary lubrication performance of neat ILs is dominated by the Lambda ratio. A correlation is found between the contact angle, wear-scar diameters and friction coefficient. In POM–POM contacts, NTf2− containing ILs do exhibit the largest friction meanwhile full film lubrication occurs in PDMS–PDMS contacts. MR fluid lubricated contacts operate within the boundary regime. However, friction levels are significantly lower than polyalphaolefin PAO based conventional MR fluids. SCN−-based ILs do provide the largest friction coefficients.

Theoretical and experimental evaluation of the flow behavior of a magnetorheological damper using an extremely bimodal magnetic fluid

The flow behavior of a magnetorheological (MR) fluid, consisting of iron particles dispersed in a ferrofluid carrier (‘MRFF’) in a commercial monotube MR shock absorber is studied. The magnetorheological properties of the MRFF suspensions are compared with those of a conventional oil-based MR fluid (‘MRF’). The mechanical behavior of the MR damper, filled with the MRFF or alternatively with the MRF, is characterized by means of different oscillatory force–displacement and force–velocity tests. The MR shock absorber has an internal electromagnet that generates a controlled magnetic field in the channels through which the MR suspensions flow under operation conditions. The results obtained indicate that the damper filled with MRFF shows a reliable and reproducible behavior. In particular, the response of the shock absorber can be controlled to a large extent by adjusting the electromagnetic current, showing a response that is independent of the mechanical and magnetic history of the MRFF. The non-linear hysteresis model proposed for predicting the damping force provides good agreement with the experimental results when the MRFF is employed. The improved response of the damper loaded with ferrofluid-based MRFF (instead of the conventional MRF) is explained considering the physical properties and the internal structure of the suspension.

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.

Torque Enhancement for a New Magnetorheological Brake

The conventional magnetorheological fluid (MR) brake has been used as resistant sources for specific applications. However, the limited torque prevents it to be widely commercialized. This paper presents a new MR brake that improves the brake torque by enlarging the magnetic field strength. The unique structure is formed by multiple electromagnetic poles surrounded by several coils. Various input power supplies and geometrical dimensions have been offered. The effects of brake structure and input power for torque enhancement were investigated. The design with maximized torque based on optimal input power has been found using Sequential Nonlinear Programming (SLNP) optimizer. The operation concept of the new MR brake was confirmed by the magnetic simulation results. It concluded that the brake archives high braking torque, which promises for future applications.