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Elastohydrodynamic Film Study under Impact Loading and Lateral Vibrations
Frýza, Josef ; Bakolas, Vasilios (referee) ; Habchi, Wassim (referee) ; Křupka, Ivan (advisor)
Disertační práce se zabývá chováním a odezvou elastohydrodynamického (EHD) mazacího filmu za neustálených provozních podmínek. V úvodní části práce jsou shrnuty poznatky z oblasti EHD mazání; od jeho historie, přes základní mechanismy mazání a používané experimentální metody, až po nedávno publikované studie zaměřené na transientní podmínky. Hlavním cílem práce bylo experimentálně objasnit vliv provozních parametrů a reologických vlastností maziv na chování mazacího filmu v bodovém kontaktu při jeho nárazovém zatěžování a vystavení příčným vibracím. Za tímto účelem byla vyvinuta laboratorní zařízení umožňující měření rozložení mazacího filmu a tření za kontrolovaných nestacionárních podmínek. Experimenty odhalili zásadní roli přibližovacích a zatěžovacích rychlostí na formování stlačených mazacích filmů při nárazovém zatěžování. Výsledky byly srovnávány s nedávným teoretickým řešením. Bylo ukázáno na jeho nedostatky, jež byly následně odstraněny implementací empirických vztahů zohledňujících reologii maziv. V případě příčných vibrací byly nalezeny hranice selhání mazacího filmu a určeny vztahy popisující vliv příčných vibrací na centrální tloušťku filmu a její fluktuace jednotně pro všechny maziva. Závěrečná část práce poskytuje nový pohled na reologii maziv pomocí inovativního přístupu měření třecích reakcí maziva současně ve dvou směrech kontaktu za podmínek příčných vibrací. Tyto původní výsledky rozšiřují pochopení mechanizmů EHD mazání a mohou být použity k dokonalejším návrhům strojů, a vylepšit tak jejich účinnost, spolehlivost a životnost.
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Lithic function and its application in archeology
Krásná, Soňa ; Popelka, Miroslav (advisor) ; Květina, Petr (referee) ; Hroníková, Linda (referee)
The goal of the thesis is to find the way how to apply use-wear analysis as well as functional analysis to archaeological assemblages of selected artefacts from Central European archaeological contexts, namely lithics (chipped stone artefacts) and obtain the greatest potential from the analysis. Thesis consists of: current state in the field of functional studies research worldwide, method of use-wear application in connection with material science knowledge, especially tribology. Use-wear analysis is applied to the selected lithic artefacts from Paleolithic to Eneolithic Periods. The results of this work are based on the following microscopic approaches: low power approach (LPA), high power approach (HPA), scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). There are described and stated differences in potential of above mentioned approaches in connection with specific archaeological artefacts (assemblages of artefacts). The question answered in the conclusion is how to apply the above mentioned methodological approaches in application to various archaeological materials (period, number, context etc.) to obtain the greatest informational potential from the material analysed. Work is concluded with specific terminology from the field of tribology and use-wear analysis...
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Tribotechnical diagnostics of oils
Pokorný, Ondřej ; Frýza, Josef (referee) ; Svoboda, Petr (advisor)
The purpose of this bachelor’s thesis is compile an overview of currently used sensors for real-time oil analysis. The paper contains a record of knowlenge in field of wear and tribotechnical sensors and determines the appropiate behavior of the tribological system for predictive maintenance. In the next part of the thesis are evaluated the introduced sensors and with help of obtained informations is assembled diagnostic for monitoring the state of gearbox of wind power plants.
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Radial Slide Bearing Analysis Using Advanced Computational Methods
Orbán, Tomáš ; Dlugoš, Jozef (referee) ; Novotný, Pavel (advisor)
This master’s thesis introduces a slide bearing analysis using the MBS software tool of FEV Virtual Engine, including real surface topography based on 3D roughness measurements. The first half of the thesis gives a brief overview about gasoline combustion engines, slide bearing usage in engines, slide bearing construction and about essential approaches for the characterization of elasto-hydrodynamic behavior. In the second half, the process of model building, rough surface measurement and preparation of analyses are described. At the end of this thesis, the results of the analyses are shown and discussed.
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Lubricant film formation in oil impregnated sintered metal parts
Látal, Roman ; Polach, Pavel (referee) ; Omasta, Milan (advisor)
This thesis deals with the experimental study of the formation of the lubricating film used for sintered metal parts impregnated with oil. The thickness of the lubricating film in a line contact is measured by the method of optical interferometry of thin lubricating films. In this thesis, the effects of various operating parameters on the formation of the lubricating film are described. The usage of impregnated lubricant leads to insufficient supply of lubricant to the contact. Individual results are significantly influenced by the degree of flooding of the contact area.
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Design and execution of additional module of laboratory equipment for measurement of friction within lubricated contacts
Stifter, Jan ; Šperka, Petr (referee) ; Frýza, Josef (advisor)
This bachelor‘s thesis presents the design and implementation of a module of laboratory device for measuring coefficient of friction and friction forces in elastohydrodynamic lubricated contacts. The module is able to measure friction forces in two perpendicular axes. A motivation for realization of this module was the absence of a similar equipment. The retrieval section of this thesis is dedicated to tribology, strain gauges (force sensors) and compliant mechanisms. The selection of the appropriate concept of the module and the force transducers is solved in the design part of thesis. The compliant mechanism with flexure hinges was designed via FEM analysis. This mechanism allows the displacement of the contact member of module in the direction of the frictional forces acting within a lubricated contact. The proposed module was manufactured, implemented in laboratory equipment and its functionality was tested. According to preliminary results, the module fulfilled the objectives of this thesis.
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An overview of method for studying and quantification of wear
Řeháková, Bára ; Urban, Filip (referee) ; Galas, Radovan (advisor)
This bachelor thesis describes ASTM test methods for determination of wear in accordance to their usefulness to ÚK in FSI VUT in Brno. The beginning concerns with types of wear and their mechanisms and with creation of new test methods. The main section deals with each of the test methods normally used by ÚK and their exact procedures. In the last part of this thesis, comparisons of these are made due to their use according to the type of material.
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The Possibilities of Displacement Increase of 4C Zetor Engine
Zloch, Jan ; Franz, Rudolf (referee) ; Dundálek, Radim (advisor)
Diploma thesis aims on mechanical design of new concept of Zetor UŘ III engine with displacement increase and solves calculations of main and pin hydrodynamic bearings of crankshaft. Creo 2 CAD software is used for preparing mechanical design of this new concept. For computation and analysis of hydrodynamic bearings multibody model of crankshaft mechanism is used with flexible FEM model of crankshaft for solving dynamics of mechanism and performing hydrodynamic analysis of bearings in FEV Virtual Engine. Results of this diploma thesis demonstrate the feasibility of new concept of engine and serve as a basis for next engineering tasks before realization of concept.
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Mechanical activation of chemical reactions at interfaces of MDF composites
Matoušek, David ; Másilko, Jiří (referee) ; Šoukal, František (advisor)
The thesis deals with study of mechnochemical activation of chemical reactions at interphase of MDF composites. MDF composites are high-perspective composite materials on polymer-cement base. They excel especially in terms of flexural strengths. High flexural stregth is caused by binding interactions between the polymer and the cement. This interactions arise due to mechanochemical activation of raw material mixture at the stage of production. This work focuses on the creation of artificial cement-polymer interphase by contacting the surfaces of two molded tablets (polyvinyl alcohol and monocalcium aluminate), activation of chemical reactions at interphase by means of specially designed appartus, which achieves good plane-parallelism of activation surfaces and good definability of activation conditions (shear rate, pressure). After experiments under different conditions, the activated surfaces are analyzed by SEM, EDS, XPS and FT-IR.
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