The Effect of the Exposure-In-Oil on the Contact Angle of the Polymers Forming Sliding Layers in Hydrodynamic Bearings (original) (raw)
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Tribological Behaviour of Polymer Bearings Under Dry and Water Lubrication
International Journal Sustainable Construction & Design, 2013
This study attempts to evaluate the performance of polymer journal bearings (PET and UHMWPE) sliding against Inconel stainless steel in both dry and lubricated condition. Four types of ‘lubricant’ are included: distilled water; demineralized water; tap water and river water. The tests were carried out in a so called “Stribeck” configuration with a projected pressure of about 0.3 MPa at room temperature and sliding speed ranging from 0 to 1.07 m/s respectively. The study indicates that polymer bearings with four types of water lubricant give better tribological behaviour compared to those in dry sliding contact. Besides, with water lubrication, UHMWPE shows low friction at starting, but it does not go down much over the course of the tests. Meanwhile, although PET indicates quite higher friction at the beginning, it then shows a clearly decreasing trend.
Effect of shaft roughness and pressure on friction of polymer bearings in water
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2013
In this study, the frictional behavior of selected commercially available unfilled polymers, namely, polyether ether ketone, polytetrafluoroethylene, polyethylene terephthalate, and ultra-high molecular weight polyethylene against an Inconel shaft was investigated using a journal bearing test configuration in water-lubricated sliding contact. Dynamic friction curves were obtained for various shaft roughness values and polymer combinations. The results showed a significant influence of shaft surface roughness on running-in and steady state friction in water-lubricated conditions. Contact angle measurements revealed a significant increase in wettability of Inconel counterfaces. The X-ray photoelectron spectroscopy (XPS) analysis of the surfaces suggests formation of a reaction layer on worn Inconel surfaces when sliding against the polymers. The influences of counter surface roughness and load on frictional response of polymers were studied through intermittent tests by obtaining dyna...
Friction of some commercial polymer-based bearing materials against steel
Tribology International, 1982
A tri-pin-on-disc tribometer has been used to determine coefficients of friction, u, given by some polymer-based bearing materials sliding on mild steel over a wide range of loads and speeds, both dry and lubricated. At constant sliding speed, values of # for both the dry and lubricated polymers were virtually independent Of load over the range (moderate to heavy) used. The frictional properties are thus presented in terms of the variation of # with sliding speed, these values being representative of all but lightly loaded applications. Under unlubricated conditions the plastics tested varied considerably in performance, the lowest friction being obtained with a filled polyethene and the highest with a polyurethane. Paraffin oil lubrication significantly reduced friction in all cases
Journal of Non-Newtonian Fluid Mechanics, 1983
A small, fixed cylinder attached to a load cell almost touches a larger, rotating cylinder (axes parallel). When a Newtonian liquid is introduced into the gap as a lubricant, the normal load and coefficient of friction are in reasonable agreement with theoretical predictions. When elastico-viscous polymer solutions are used, however, at progressively increasing polymer concentrations, the load increases to over 20 times the theoretical prediction and the coefficient of friction falls to half its theoretical value.
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2019
The problem of the decrease in power loss due to friction stands permanent. One of the approaches to the solution of the problem is the application of polymer additives in order to modify the rheological properties of oils. The present theoretical work is dedicated to the analysis of experimental results of a study on polymethacrylate additives’ influence on friction that were obtained in the laboratory of Solid Mechanics of the Poitiers University. A simulation model developed in the present paper is based on the generalised Reynolds equation that takes heterogeneity of viscosity properties into account. The Reynolds equation was modified and rewritten in the bicylindrical coordinates. The geometry of the flow region could thus be described more accurately and the numerical solution could be obtained over a grid with an adaptive step. Analysis of numerical results along with experimental results allowed the identification of relationship between contents of polymer-containing oils ...
Lubricants
The hydrodynamic lubrication and thermal analysis of tilting pad thrust bearings has been a major subject for many studies in the field of tribology. There is only a limited number of studies regarding thrust bearings with coated surfaces. The purpose of this study is to build a parametric, iterative algorithm in order to perform a complete thermal and hydrodynamic lubrication analysis for pivoted pad thrust bearings with coatings. The analytical model is mainly based on the energy, continuity and Navier-Stokes equations, which are solved numerically with the Semi-Implicit Method for Pressure Linked Equations Consistent (SIMPLEC) method. The analysis focuses on a single pivoted pad of the thrust bearing. The thermal properties of the coating material are taken into account and the resulting thermal and flow fields are solved. The basic hydrodynamic and tribological characteristics are calculated for an uncoated, a Babbitt coated, a PTFE coated and a diamond like carbon (DLC) coated pivoted pad thrust bearing. The pressure and the film thickness distribution, as well as the load capacity and the frictional forces, are determined for several pad positions and velocities of the rotor. A mineral oil lubricant is used to estimate the shear thinning or thickening effects on the pad tribological performance. The results indicate that pads coated with PTFE and DLC show lower friction forces compared to the common steel and Babbitt applications. At the same time, the DLC coating seems to affect the bearing's flow and thermal fields less than the PTFE, making it more suitable for thrust bearings applications.
Tribology International, 2012
The viscosity of polymer-containing oils decreases at high shear rates; it would follow that reducing viscosity enhances performance by decreasing frictional losses in journal bearing lubrication but impedes performance by increasing metal contact. However, as our previous study confirmed, no such trade-off occurred. It is also considered that the first normal stress difference (N1) of polymer helps to move the shaft in the direction of increasing oil film thickness. In order to analyze the effect of polymers, the authors experimentally and theoretically evaluated bearing performance using a base oil and polymer-containing oils.
Lubricants, 2018
Nowadays, hydropower plants are forced to have more frequent power control and the self-lubricated bearings used in the applications are one of the most critical components affected by the continuously changing operating conditions. In this study, microstructure and composition of two commercially available bearing materials (Orkot TXM Marine and Thordon ThorPlas) used in hydropower turbines were studied. In addition, the influence of sliding speed and applied pressure on the friction and wear behavior of the materials was investigated systematically for dry sliding conditions. The bearing materials were characterized using X-ray microtomography, Nuclear Magnetic Resonance (NMR) spectroscopy and Inductively Coupled Plasma-Sector Field Mass Spectrometry (ICP-SFMS) techniques. Friction and wear tests were carried out with a polymer pin sliding against a stainless steel (SS2333) plate with a linear reciprocating motion. Test conditions were: room temperature, 9-28 MPa pressure and 10-40 mm/s sliding speed ranges. Surface analysis of the polymer pins and the wear tracks were performed by optical profilometry, Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) techniques. Test results show that, for both materials, the coefficient of friction (COF) is decreasing at higher pressures. Surface analysis reveals higher concentrations of solid lubricants in the transfer layers formed at higher pressures, explaining the decrease in COF. Furthermore, the specific wear rate coefficients are increasing at higher sliding speeds, especially at lower pressures. Results of this study demonstrate that, under dry sliding conditions, changes in sliding speed and pressure have a significant influence on the tribological behavior of these bearing materials.
2016
Polymer thickened oils are the most preferred materials for modern lubrication applications due to their high shear. The present paper explores a lubrication mechanism in sliding contact lubricated with polymer thickened oil considering cavitation. Investigations are carried out by using a numerical method based on commercial CFD (computational fluid dynamic) software ANSYS for fluid flow phenomenon (Fluent) to assess the tribological characteristic (i.e. hydrodynamic pressure distribution) of lubricated sliding contact. The Zwart-Gerber-Belamri model for cavitation is adopted in this simulation to predict the extent of the full film region. The polymer thickened oil is characterized as non-Newtonian powerlaw fluid. The simulation results show that the cavitation lead lower pressure profile compared to that without cavitation. In addition, it is concluded that the characteristic of the lubrication performance with polymer thickened oil is strongly dependent on the Power-law index of lubricant.
Transition from Boundary Lubrication to Hydrodynamic Lubrication of Slider Bearings
IBM Journal of Research and Development, 1974
The transition from boundary lubrication to fully hydrodynamic lubrication is investigated for air-lubricated slider bearings using the electrical resistance method. Intermittent contacts are shown to exist even under conditions for which the numerical solution of the Reynolds equation or white light interferometry predicts steady state spacings in the spacing region from 0.125 to 0.25 pm. The transition is similar to the one found in the presence of liquid films, being influenced for a given surface roughness of disk and slider by load, speed, and hydrodynamic design.