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Experimental Study of Lubrication Films Formation During Start-up and Reversal Motion of Rubing Surfaces
Svoboda, Petr ; Dzimko, Marián (referee) ; Čermák, Jan (referee) ; Dobeš, Petr (referee) ; Křupka, Ivan (advisor)
This dissertation is focused on the effects of both artificially produced and real roughness features on mixed lubrication film formation during start-up and reversal of non-conformal contacts operated under rolling/sliding conditions. The start-up operation of mixed lubricated contacts represents one of the transient conditions that bring the risk of the surface damage because of asperities interactions. Chromatic interferograms captured by CMOS high-speed camera during start up of the motion enabled to observe the detailed changes in lubrication film caused by surface features. The observation of the effects of surface dents artificially produced on the ball surface helped to understand better the behaviour of real surface topography. It was found that the presence of shallow surface features can help to separate mixed lubricated rubbing surfaces more efficiently than it could be suggested from the results obtained with smooth surfaces. It can be suggested from the obtain results that properly designed topography of the rubbing surfaces can help to reduce the asperities interactions under transient operational conditions.
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Study of the effects of ellipticity parameter on lubrication film shape
Pavlík, František ; Dzimko, Marián (referee) ; Křupka, Ivan (advisor)
Diploma thesis deals with elastohydrodynamic lubrication of point contacts, which surfaces are influenced by topography and velocity vector of one rubbing surface is misaligned. Author summarizes knowledge of previously published research articles, which fundamentally enrich current state of knowledge. Diploma thesis contains experimental measurement results of the film thickness and the way of lubrication film formation in elliptical contact for different ellipticity parameters, kinds of rubbing surfaces and angles of the velocity vector. New findings have helped to better understand the behaviour of highly loaded lubricated contacts taking place in machine components and completed the current state of knowledge with results that can be used in next thorough study of this issue.
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Realization of the device for measurement of electromagnetic waves scattering from structure of solar cells
Brilla, Pavol ; Březina, Tomáš (referee) ; Ohlídal, Miloslav (advisor)
The master thesis discusses the principles, design and realization of the original device for measuring of the electromagnetic radiation scattering in the structure of solar cells. It follows the results of a previous project "Analýza optických vlastností solárných článku" (ev.n.FT-TA3/142) and as well as knowledge gained from Ing. Vladimir Grundling’s master thesis, which has been done under this project. The subject of this thesis was to make a device for measuring of the electromagnetic radiation scattering in the visible spectrum. The aim of this work is an innovation of the previous device, so that the electromagnetic radiation scattering in the near infrared spectrum can be studied. This makes the possibility to qualify the influence of the rear surface of an active part of solar cell on electromagnetic radiation scattering, i.e., on the conversion efficiency of solar energy into electric. For this reasons it was necessary to modify the device, so that we can change the radiation source and detector because of the transparency of silicon wafers for the near infrared area. The work is supported by the project „Barevné solární články s vysokou účinností pro architektonické aplikace“ (FRTI1/168) in cooperation with Solartec s.r.o.
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Analysis of solar cell surface features
Lipr, Tomáš ; Macků, Robert (referee) ; Škarvada, Pavel (advisor)
This thesis is focused on the study of electrical and optical properties of solar cell samples using the near field optical microscope. Process of the image formation is described. Artefacts which are presented on some of topography images are described, too. There are some timing problems with measuring of the sample local electric response. If the measuring and scanning devices are not in the time synchronization there will be some difficulties with measured data representation and 2D image offline formation. Created electronic for SNOM and measuring devices synchronization is presented.
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Effects of pulsating water jet on materials with variously modified surface
Klich, Jiří ; Klichová, Dagmar ; Hlaváček, Petr
The paper deals with determination of erosion effects of pulsating water jet impinging the surface of aluminium alloy samples treated by various techniques (rough and fine milling, planing and rolling). The influence of the initial surface topography on the final topography of the sample exposed to pulsating water jet was investigated. Erosion of surface layer was analysed and discussed with respect to the traversing velocity of the jet. It was found, that properties of the initial surface have a significant impact on the final topography. Degree of erosion of the surface was determined by the measurement of surface parameter Ra.
Fulltext: content.csg -  DOC
Plný tet: UGN_0398577 - DOC
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Study of the surface topography created by pulsating water jet
Klich, Jiří
The paper has followed to study of the surface topography created by the pulsating water jet. It presents a way to evaluate the surface topography created by the unconventional method. Based on data analysis and subsequent interpretation is described the surface generated pulsating water jet. Knowledge of this description is very important for dimensioning the optimum technological factors pulsating water jet in relation to the workpiece material and the required quality of the finished surface.
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