ANALYSIS OF THE POTENTIAL USAGE OF SELECTED MAGNETIC FLUIDS IN THRUST SLIDE BEARINGS

Tribologia ◽  
2016 ◽  
Vol 269 (5) ◽  
pp. 41-49 ◽  
Author(s):  
Wojciech HORAK ◽  
Józef SALWIŃSKI ◽  
Marcin SZCZĘCH
Keyword(s):  
Magnetic Field ◽  
Rheological Properties ◽  
Mechanical Energy ◽  
Magnetic Fluids ◽  
Magnetorheological Fluids ◽  
Machine Design ◽  
Rheological Characteristics ◽  
New Horizons ◽  
Controlled Systems ◽  
Ferromagnetic Fluids

Magnetic fluids are substances whose rheological properties can be actively influenced by treatment with a magnetic field. Two main types of magnetic fluids can be distinguished: ferromagnetic fluids, and magnetorheological fluids. Ferrofluids are mostly used in sealing engineering, whereas magnetorheological fluids are usually applied in controlled systems for the dissipation of mechanical energy, like brakes and dampers. The ability to control the rheological properties of magnetic fluids opens new horizons for development in machine design, among others in the areas of bearing engineering. The paper presents a comparative analysis of the rheological characteristics of selected magnetic fluids with a focus on the possible areas of the application of these substances in bearing engineering.

Visualizing Rheological Mechanism of Magnetorheological Fluids

2021 ◽  
Author(s):  
Yurui Shen ◽  
Dezheng Hua ◽  
Xinhua Liu ◽  
Weihua Li ◽  
Grzegorz Krolczyk ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Rheological Properties ◽  
Magnetic Dipole ◽  
Laser Scanning ◽  
Magnetic Particles ◽  
Three Dimensional ◽  
Confocal Laser Scanning Microscope ◽  
Magnetorheological Fluids ◽  
Confocal Laser ◽  
Observation Method

Abstract In order to study the rheological properties of aqueous magnetorheological fluids (MRFs) from microscopic point of view, an experimental observation method based on the fluorescence confocal laser scanning microscope is proposed to clearly produce the chain shape of the magnetic particles. Firstly, the mathematical model of the magnetic particles is established in a magnetic field using the magnetic dipole theory, and the MRFs with different fraction volumes and different magnetic fields are investigated. Furthermore, an aqueous MRFs experiment is prepared, in which the magnetic particles are combined with Alexa 488 fluorescent probe. On this basis, an observation method is innovatively developed using two-dimensional (2D) and three-dimensional (3D) image analysis by the fluorescence confocal microscope. The rheological mechanism of the aqueous MRFs is investigated using four different types of MRFs in an external magnetic field. The analysis results demonstrate that the simulation and experimental rheological properties of the MRFs are consistent with the magnetic dipole theory. Moreover, the proposed method is able to real-time observe the rheological process of the MRFs with a very high resolution, which ensures the correctness of the analysis results of the rheological mechanism.

MAGNETORHEOLOGICAL FLUIDS AND THEIR PROPERTIES

2005 ◽  
Vol 19 (01n03) ◽  
pp. 593-596 ◽  
Author(s):  
J. M. HE ◽  
J. HUANG
Keyword(s):  
Magnetic Field ◽  
Yield Strength ◽  
Rheological Properties ◽  
Yield Stress ◽  
Applied Magnetic Field ◽  
Magnetorheological Fluids ◽  
Mr Fluid ◽  
Variable Yield ◽  
Mr Fluids

Magnetorheological (MR) fluids are materials that respond to an applied magnetic field with a change in their rheological properties. Upon application of a magnetic field, MR fluids have a variable yield strength. Altering the strength of the applied magnetic field will control the yield stress of these fluids. In this paper, the method for measuring the yield stress of MR fluids is proposed. The curves between the yield stress of the MR fluid and the applied magnetic field are obtained from the experiment. The result indicates that with the increase of the applied magnetic field the yield stress of the MR fluids goes up rapidly.

Microstructure evolution based particle chain model for shear yield stress of magnetorheological fluids

2020 ◽  
Vol 32 (1) ◽  
pp. 49-64
Author(s):  
Yongbo Peng ◽  
Pei Pei
Keyword(s):  
Magnetic Field ◽  
Rheological Properties ◽  
Microstructure Evolution ◽  
Volume Fraction ◽  
Magnetorheological Fluids ◽  
Model Verification ◽  
Structure Evolution ◽  
Chain Model ◽  
Shear Model ◽  
Proposed Model

To predict the shear stress of magnetorheological fluids (MRFs) under magnetic field and shear flows, a meso-microscale shear model is proposed based on the entire course of particle aggregates and chains. For this purpose, a systematic study on the microstructure evolution and rheological properties of MRFs is conducted by using molecular dynamics simulations. An efficient chain identification technique is introduced to count the number of particle chains within the suspension system. From the perspective of particle-level simulations, the microstructured behavior of MRFs involving particle aggregation and internal structure evolution of magnetorheological suspensions are addressed. Shear properties of MRFs derived by the proposed model are studied, and model verification by comparison with previous experimental data and predictions of the existing structural viscosity model is included as well. It is revealed that the proposed meso-microscale shear model exhibits satisfactory accuracy and efficiency for describing the rheological properties of MRFs. Besides, the critical factors linked with rheological properties of MRFs such as magnetic field strength, particle volume fraction and shear rate, are analyzed, further demonstrating the applicability of the proposed model in design and optimization of MRFs.

THE INFLUENCE OF SELECTED FACTORS ON AXIAL FORCE AND FRICTION TORQUE IN A THRUST BEARING LUBRICATED WITH MAGNETORHEOLOGICAL FLUID

Tribologia ◽  
2016 ◽  
Vol 269 (5) ◽  
pp. 51-61 ◽  
Author(s):  
Wojciech HORAK ◽  
Józef SALWIŃSKI ◽  
Marcin SZCZĘCH
Keyword(s):  
Magnetic Field ◽  
Rheological Properties ◽  
Magnetic Fluid ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Magnetic Field Gradient ◽  
Magnetic Fluids ◽  
Carrier Fluid ◽  
Wide Range ◽  
The Magnetic Field

Magnetic fluids belong to the class of materials in which rheological properties can be controlled by magnetic fields. Magnetic fluids are suspensions of ferromagnetic particles in a carrier fluid, and the magnetic field can change their internal structure. This phenomenon is fully reversible, almost instantaneously. The test results of a hydrostatic bearing lubricated by magnetic fluid are shown in the publication [L. 7]. It has been shown that the use of MR fluids as a lubricant allows high stiffness of the bearing to be obtained regardless of the height of the bearing gap. The publication [L. 8] presents the results of a thrust bearing lubricated by magnetic fluid with no external feed pump. The load capacity of the bearing was achieved by a self-sealing effect. This effect is associated with the ability to hold a magnetic fluid in a predetermined position through the magnetic field. This is caused by the appropriate geometry of the bearing surface. This effect retains the flow of the magnetic fluid out of the bearing gap as a result of the occurrence of a magnetic barrier, which counteracts the movement of the magnetic fluid. This barrier is a result of a local increase or decrease in magnetic induction similar to magnetic fluid seals. Another phenomenon highlighted in [L. 9, 10, 11] is the generation in the magnetic fluid of additional pressure due to the interaction of the magnetic field gradient. The result is an additional buoyancy force. When selecting a magnetic fluid for application in the thrust bearing, a number of factors should be taken into account. In addition to the parameters describing the typical lubricant, such as lubricity, corrosion properties, and work at high temperatures, the magnetic fluid used in the friction zone should allow a wide range of the rheological properties to be obtained due to changes in the magnetic field intensity. It is also important that the magnetic fluids have the ability to generate the appropriate value of the normal force due to the magnetic field.

THE ANALYSIS OF THE WORKING CONDITIONS OF A THRUST SQUEEZE BEARING WITH A MAGNETORHEOLOGICAL FLUID OPERATING IN THE OSCILLATORY COMPRESSION MODE

Tribologia ◽  
2019 ◽  
Vol 285 (3) ◽  
pp. 45-50
Author(s):  
Wojciech HORAK ◽  
Marcin SZCZĘCH
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Rheological Properties ◽  
Working Conditions ◽  
Axial Force ◽  
Magnetorheological Fluid ◽  
Magnetorheological Fluids ◽  
Operating Characteristics ◽  
Carrier Fluid ◽  
Load Conditions

The operating state of thrust plain bearings is a function of many parameters, both geometric and related to load conditions. Besides the methods of controlling bearings of this type used so far, new possibilities of modelling their operating characteristics by using substances with controlled rheological properties as a lubricant can be pointed out. Magnetorheological fluids create such a possibility. These are suspensions of particles with magnetic properties in a carrier fluid (usually in mineral or synthetic oil). The influence of magnetic field on this type of fluids changes their rheological properties. This process is almost instantaneous and fully reversible. The paper presents the results of investigations of a thrust squeeze bearing lubricated with magnetorheological fluid. The aim of the study was to determine the influence of selected factors on the axial force as a result of the oscillatory squeeze load.

Enhanced magnetorheological effect and sedimentation stability of bimodal magnetorheological fluids doped with iron nanoparticles

2020 ◽  
pp. 1045389X2092483 ◽  
Author(s):  
Wanning Zhu ◽  
Xufeng Dong ◽  
Hao Huang ◽  
Min Qi
Keyword(s):  
Magnetic Field ◽  
Rheological Properties ◽  
Carbonyl Iron ◽  
Iron Nanoparticles ◽  
Arc Discharge ◽  
Magnetorheological Fluids ◽  
Mechanism Study ◽  
Adsorbed State ◽  
Sedimentation Stability ◽  
Magnetorheological Effect

The improvement of properties of magnetorheological fluids and mechanism study has long been a classic area within the field of magnetorheological materials. This article was undertaken to dope the iron nanoparticles synthesized by direct current electric arc discharge with the traditional carbonyl iron powders to prepare bimodal magnetorheological fluids with different doping ratios. Their rheological properties and sedimentation stability were evaluated to explore the influence rules and mechanisms. The results indicate that the effect of the addition of iron nanoparticles on rheological properties under magnetic field is a combination of two opposing factors such as the strengthening of the structure and the weakening of magnetization. The sedimentation stability of the bimodal magnetorheological fluids improved significantly with the increase in the proportion of iron nanoparticles, which is attributed to the help of both free state and adsorbed state iron nanoparticles in magnetorheological fluids. Furthermore, within a specific magnetic field strength range, the bimodal magnetorheological fluids with a small proportion of iron nanoparticles can achieve an improvement in both rheological property and sedimentation stability compared with carbonyl iron particles–based magnetorheological fluids.

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