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EN
In this paper authors present results of measurements of slide journal bearings surface topography measured with a profilometer and an atomic force microscope (AFM). Surface topography of investigated bearings (i.e. journals and sleeves) was measured using the Hommeltester T8000- R60 profilometer. The results of these measurements give information about micro-grooves dimensions and location. Measurements of surface topography were made for journals and sleeves of slide journal micro-bearings from personal computers fans, with the Atomic Force Microscope NT-206 produced in MTM in Minsk, Republic of Belarus. The results of measurements of surface topography were presented in the form of surface topography maps, threedimensional graphs and some examples of selected cross-sections of investigated surfaces in the form of profile graphs. The values of profile roughness parameters Ra and Rq and the distance between maximum peak height and maximum valley depth are presented as well. The application SurfaceXplorer registered trademark was used for processing and visualization of the data obtained from AFM NT-206, which besides from generating 2D, 3D and profile diagrams, was used to calculate and draw graphs of height distribution. In this research authors used two identical sets of micro-bearings. The investigated bearings are: a) Kama Flow SP0825FDB12H fan with grooved surface of bearing sleeve, b) Xilence Case fan which sleeve surface was without grooves. First set of that micro-bearings functioned for a year at rated RPM continuously (i.e. 24 hours a day). Second set of the same micro-bearings also functioned for a year at rated RPM, but in intermittent mode (i.e. 15 minutes on, 15 minutes off). On the surfaces of studied micro-bearings some microgrooves can be found in form of herringbone, with depth about 1-2..m and width 100-150..m. Received information about microgrooves geometry will help to develop proper theory of hydrodynamic lubrication for micro-bearings with microgrooves and allows determining how the mode of operating affects on the wear of co-operating surfaces.
EN
In this paper authors present results of measurements of slide journal bearings surface topography measured with an atomic force microscope (AFM). The results of measurements of surface topography were presented in the form of surface topography maps, three-dimensional graphs and some examples of selected cross-sections of investigated surface in the form of profile graphs. Measurements of surface topography were made for journals and sleeves of slide journal micro-bearings from personal computers' hard drives and fans, with the Atomic Force Microscope NT-206 produced in MTM in Minsk, Republic of Belarus. The values of profile roughness parameters Ra and Rq and the distance between maximum peak height and maximum valley depth are presented as well. The application SurfaceXplorerŽ was used for processing and visualization of the data obtained from AFM NT-206, which besides from generating 2D, 3D and profile diagrams, was used to calculate and draw graph of height distribution. Surface pictures of investigated bearings sleeves were made with the optical microscope Zeiss Axiovert 25+. That measurements give information about micro-grooves dimensions and location. On the surfaces of studied micro-bearings some micro-grooves can be found in form of herringbone, with depth about 1.5mi m and width 150/mi m. Received information about micro-grooves geometry will allow to develop proper theory of hydrodynamic lubrication for micro-bearings with micro-grooves. Topography of surfaces of investigated journal micro-bearings will be reconsidered after exploiting them proper amount of time.
EN
In this paper are assumed micro-ridges and micro-grooves on the Journal and bearing sleeve surfaces. Friction on the boundary layer of the body moving in the oil at high Reynolds numbers may be decreased due to such asculpturing of the surface. The grooved scale of the shark skin is an example of such tribological systems. There size ranges of the grooves are from 200 jum to 400/jm. The surface of the each scale contains parallel groove between so-called ribbed directed almost parallel to the longitudinal body axis. An explanation of the shark skin effect has been proposed recently for the micro-bearing surfaces shapes execution. In the boundary layer, not only longitudinal micro-turbulence but also cross-directed micro-turbulence occurs. The longitudinal grooves of the shark and bearing surface prevent the appearance of the cross-directed micro-turbulences. Forces of the streaming oil in bearing or micro-bearing gap act on the bearing surface in two different ways. On one side, the oil generates the pressure directed normally to the surface of the Journal surface and is responsible for inertiaforces. On the other side, friction or shearing force acts tangentially to the bearing surface. The resulting force depends on the geometry of the body, its relative dimensions to the oilflow and on such characteristics of the oil as its density, viscosity and velocity.
PL
Jednym z głównych wyzwań realizowanym od niemal dwóch dekad w wielu ośrodkach badawczych jest próba zbudowania wysokoobrotowej mikromaszyny przepływowej w technologii MEMS. Wyzwanie to związane jest z zapotrzebowaniem w zakresie maszyn przetwarzających energię z dużą gęstością mocy w skali mili i mikro. Zaprezentowane wyniki obliczeń numerycznych mają na celu teoretyczne porównanie działania ultrakrótkich mikrołożysk poprzecznych o zmiennej geometrii dla dwóch różnych systemów podparcia segmentów oraz łożysk o stałej geometrii. Zasadniczym i osiągniętym celem takiego porównania jest wykazanie, że przy odpowiednim doborze parametrów elastycznego podparcia segmentów możliwe jest uzyskanie zadawalających parametrów funkcjonowania mikrołożyska poprzecznego o niskim stosunku długości do średnicy (L/D<0.1). W obliczeniach posłużono się nieliniowym modelem łożyska poprzecznego o zmiennej geometrii, który podczas prowadzonych badań układu łożyskowego w powiększonej skali wykazywał dobrą zgodność wyników obliczeń teoretycznych z eksperymentem. Badania, których wyniki tutaj zaprezentowano, są częścią projektu badawczego prowadzonego w ramach współpracy IMP PŁ i ONERA.
EN
Aspirations for construction of a high-speed Power MEMS micro-turbomachinery have been one of major challenges in many research centers all over the world for almost two decades. This tendency results from the demand for micro-scale devices which are able to process energy with high power density. The presented numerical investigations have been conducted in order to compare theoretically the ultra-short tilting pad gas journal bearing with two different pivot systems and the corresponding multi-lobe gas journal bearing applied in the Power MEMS. The fundamental goal of this comparison is to show that it is possible to achieve advantageous performance parameters of the journal micro-bearing with a low length to diameter aspect ratio (L/D<0.1), provided the parameters of elastic pivots are properly selected. The non-linear model of the tilting pad gas journal bearing which yielded a good agreement of numerical calculation results with the experiment in the macro-scale has been used in the computations. The investigations discussed herein are a part of the research project conducted within the co-operation between the Institute of Turbomachinery Technical University of Lodz (Poland) and The Office National d'Etudes et de Recherches Aeronautiques (ONERA, France).
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