Investigating rheological properties of low-content Fe3O4 magnetic fluid using capillary rheometer

Preliminary analysis of magnetorheological fluid usability in fluid lubricated bearings has been described in the present study. Results of the study aimed at rheological properties of chosen fluids, which possess magnetic properties (both ferrofluids and magnetorheological fluids) with respect to their application in slide bearings have been presented Preliminary analysis of potential advantages related with the magnetic fluid bearing construction was carried out. Results of measurements of normal force developed within magnetorheological fluid and ferrofluid in result of magnetic field action at various shear rate values have been presented.

Download Full-text

Rheological Properties Related to Extrusion of Polyolefins

Polymers ◽

10.3390/polym13040489 ◽

2021 ◽

Vol 13 (4) ◽

pp. 489

Author(s):

Evan Mitsoulis ◽

Savvas G. Hatzikiriakos

Keyword(s):

Rheological Properties ◽

Slip Velocity ◽

Wall Slip ◽

Molecular Characteristics ◽

Capillary Rheometer ◽

Rheological Models ◽

Cross Model ◽

Slip Effects ◽

Best Fitting ◽

Temperature And Pressure

Rheological properties related to the extrusion of polyolefins are the shear viscosity, the elongational viscosity, the slip velocity and their temperature- and pressure-dependencies. These properties are measured in the rheology lab mainly via a parallel-plate rheometer and a capillary rheometer. Then appropriate rheological models have to be used to account for all these properties. Such models are either viscous (e.g., the Cross model) or viscoelastic (e.g., the K-BKZ model). The latter gives the best fitting of the experimental data and offers excellent results in numerical simulations, especially in extrusion flows. Wall slip effects are also found and measured by rheometric flows. Modeling of extrusion flows should make use of appropriate slip models that take into effect the various slip parameters, including the effects of shear stress, molecular characteristics, temperature and pressure on the slip velocity. In this paper the importance of these properties in extrusion are discussed.

Download Full-text

Tuning magneto-rheological properties of magnetic fluid using hydrophilic fumed silica nanoparticles

Soft Matter ◽

10.1039/d1sm00806d ◽

2021 ◽

Author(s):

Xiao Liu ◽

Decai Li

Keyword(s):

Silica Nanoparticles ◽

Rheological Properties ◽

Magnetic Fluid ◽

Fumed Silica ◽

Mass Fraction ◽

Coarse Grained ◽

Fumed Silica Nanoparticles ◽

Magneto Rheological

In this paper, we study the effect of hydrophilic fumed silica nanoparticles with different mass fraction on the magneto-rheological properties of magnetic fluid, and reveal the mechanism by the coarse-grained...

Download Full-text

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

Tribologia ◽

10.5604/01.3001.0010.6588 ◽

2016 ◽

Vol 269 (5) ◽

pp. 51-61 ◽

Cited By ~ 6

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.

Download Full-text