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Friction Modification within Wheel-Rail Contact
Galas, Radovan ; Meierhofer, Alexander (referee) ; Pfaff, Raphael (referee) ; Hartl, Martin (advisor)
Předložená disertační práce se zabývá experimentálním studiem modifikátorů tření a maziv pro temeno kolejnice, které jsou aplikovány do kontaktu kola a kolejnice za účelem optimalizace adheze a redukce hluku. Hlavním cílem práce bylo objasnit vliv aplikovaného množství a složení těchto látek na adhezi v kontaktu. Hlavní pozornost byla věnována zejména potencionálním hrozbám souvisejících s kriticky nízkou adhezí, která může nastat po aplikaci těchto látek. Experimentální studium probíhalo v laboratorních i reálných podmínkách, konkrétně v tramvajovém provozu. V případě laboratorních experimentů byl využit komerční tribometr a dvoudiskové zařízení umožňující simulovat průjezd vozidla traťovým obloukem. Kromě samotné adheze bylo při experimentech sledováno také opotřebení a míra hluku. Výsledky ukázaly, že maziva pro temeno kolejnice jsou schopna poskytovat požadované třecí vlastnosti, nicméně jejich chování je silně závislé na aplikovaném množství. V případě předávkování kontaktu dochází ke kriticky nízkým hodnotám adheze, které vedou k výraznému prodloužení brzdné dráhy. V případě modifikátorů tření bylo ukázáno, že chování těchto látek je výrazně ovlivněno odpařováním základního média. Výsledky také ukázaly, že nadměrné množství částic pro modifikaci tření může způsobit kriticky nízké hodnoty adheze. U obou výše zmíněných typů produktů byl prokázán pozitivní vliv na míru opotřebení a míru poškození povrchu, zatímco významná redukce hluku byla dosažena pouze v případech, kdy došlo ke značnému poklesu adheze. V závěru této práce jsou uvedena doporučení pro další výzkumné aktivity v této oblasti.
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Rail materials and profiles in rail transportation
Svobodová, Anežka ; Kvarda, Daniel (referee) ; Galas, Radovan (advisor)
This bachelor’s thesis is focused on the issue of the choice of rail materials and profiles. The aim is to give a comprehensive overview of the current situation in Czech Republic and some other foreign countries. The first part is dedicated to rail steels with description of structure, current usage and indication of the scopes of consecutive development. In the second part, there are described the most frequent profiles, their history and the current state. This thesis includes also discussion part which compares current problems and requirements that can be significant to some possible research.
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Lubricants for bicycle chains
Brychta, Ondřej ; Navrátil, Václav (referee) ; Svoboda, Petr (advisor)
This bachelor thesis deals with the lubrication of bicycle chains. The introduction describes the basics of the friction processes, then there is an analysis of the chains used on bicycles, used materials, analysis of forces and wear in the chains. The last part is devoted to the properties of basic types of lubricants, their additives and the possibilities of their use in cycling.
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On the advanced production technology of UHMWPE joint implant part
Urbancová, Kateřina ; Sliwková, Petra (referee) ; Píška, Miroslav (advisor)
This bachelor’s thesis is dealing with the problematics of individual joint replacements. The thesis summarizes the modern materials used for making artificial joint replacements, but it concentrates mainly on the plastic femoro-tibial part of the implant, usually manufactured from ultra-high molecular weight polyethylene. This material is the best choice when manufacturing the articulating surface of the joint replacement at the moment. The thesis pays attention to the polyethylene surface treatment, as the quality of the surface affects the wear of the plastic, which is critical for the implant lifespan. The thesis also focuses on analysis of the coefficient of friction of UHMWPE in contact with the titanium femoral component. Another part of this thesis is also a wear analysis of used tibial inserts made of UHMWPE and the mechanisms of wear.
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Tribological characteristics of smart fluids
Michalec, Michal ; Čermák, Jan (referee) ; Svoboda, Petr (advisor)
The master's thesis deals with experimental study of tribological characteristics of smart fluids. Smart fluids are substances in liquid state reacting to the presence of magnetic or electric field by change in rheological properties. For possible application in devices using conventional lubricants is necessary to choose suitable smart fluid and study the influence of excitation on formation of lubricating layer, friction and wear. Comprehensive description of excitation influence is executed using three experimental devices and theoretical model for measurements parameters specification. Assessed are lubricant film thickness, friction coefficient and wear under smart fluid activation in non-conformal contact. Results show significant observable influence of smart fluids excitation on all assessed aspects. Understanding the mechanisms of smart fluids excitation can be a key step in development of intelligent devices with active external control of lubricant behaviour and character, that could lead to maintenance cost reduction and effectivity improvement.
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The effect of lubricant contamination and degradation on lubricating film behavior
Strnad, Jan ; Dzimko, Marián (referee) ; Omasta, Milan (advisor)
Lubrication contamination and degradation is one of the major causes of unexpected failure of tribological nodes. As a result, different levels of maintenance are introduced in practice, leading to a longer service life of the lubricated node. These systems often include sophisticated on-line diagnostic tools that can be used to evaluate a sample of a lubricant using certain variables such as viscosity, number of particles, humidity, dielectric constant, etc. Based on changes of these variables some systems can make corrective measures such as filtering or complete replacement of lubricant. Therefore, the aim of this experimental thesis is to determine the influence of lubrication contamination (solid particles, moisture) and degradation (oxidation) on the lubricating film behavior with respect to its limit bearing capacity. To examine the thickness of the lubricating film, friction and wear, an optical and MTM tribometer, in the ball-on-disc configuration, was used.
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Analysis of durability and costs of monolithic milling and drilling tools
Kašpar, David ; Osička, Karel (referee) ; Kalivoda, Milan (advisor)
This bachelor thesis deals with the durability of different types of monolithic drilling and milling tools made of high-speed steel and sintered carbide. The theoretical part deals with durability, possible types of wear of monolithic drilling and milling tools and related circumstances. The practical part examines the durability of different types of tools for drilling and milling, their comparison in terms of cost and productivity of machining and their impact on production costs in the production of a simple part.
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Wear of hard coatings
Černý, Libor ; Křupka, Ivan (referee) ; Omasta, Milan (advisor)
This bachelor's thesis was made as a description of the main technological methods, which are used in order to manufacture hard coatings. Applications of hard coatings are realized to improve tribological properties of components in various industries. The aim is to minimize the amount of wear and friction losses. Thesis also discusses methods of measuring the hard coatings wear. These methods are important to determine the properties of coating layers and their subsequent use. A lot of testing methods offer sufficient possibilities to test various mechanisms of wear in variety of laboratory conditions. Additionally in the end of the thesis there is an experimental wear measurement of specimen on tribometer using the "Pin on disc" method. Both size and type of the wear are evaluated by profilometer.
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