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The choice of material for the production of blade wheels of jet aircraft engines
Černý, Michal ; Hutařová, Simona (referee) ; Němec, Karel (advisor)
This bachelor's thesis provides a basic overview of the materials used in the production of turbine blades of jet aircraft engines. An aircraft engine can be divided into two parts - cold and hot part, each with very different requirements for the materials used in them. The conditions in the cold part are relatively mild and the requirements are more or less satisfied by the currently used materials. The goals for further development are primarily a reduction in density and an increase in strength and fatigue properties. The real challenge of the aerospace industry is to find materials capable of working under extreme conditions in the hot part, therefore this work devotes most of the scope to the given issue. The basic overview is created by synthesizing several sources. Most of the information is drawn from American books giving a comprehensive picture of materials and manufacturing processes for this use. After decades of research, nickel superalloys in combination with thermal coatings and cooling vents proved to be the most suitable materials. Their properties, structure and production process form the basis of knowledge on this topic. The main goal for the development is to increase the temperature at which these materials are able to function, as a higher temperature of the flue gas entering the turbine means higher efficiency and associated financial and ecological savings. Despite years of research and properties unmatched by any other material, I believe there is still room for improvement. With the advent of new technologies, the emergence of a new group of materials on a different basis than nickel superalloys is possible. A brief description of several promising newly tested groups of materials, as well as my view on the future of the industry, form the final part of this work.
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Cu-Fe-based immiscible alloys prepared by casting in a copper mold
Zabloudilová, Eva ; Němec, Karel (referee) ; Adam, Ondřej (advisor)
Immiscible alloys are characterized by a positive enthalpy of mixing. The resulting microstructure of these alloys is therefore made up of separated phases. The microstructure and mechanical properties of the material can be influenced not only by the cooling rate of the sample during casting, but also by the addition of alloying elements. This bachelor's thesis is devoted to alloys based on Cu-Fe, which is characterized by the presence of a miscibility gap. Ni, Mn, Co and Cr were selected as alloying elements. The alloys were prepared using Rapid solidification by casting into a copper mold and their microstructure, chemical composition and hardness were subsequently evaluated. Subsequently, the influence of individual elements on the resulting properties of the alloys was evaluated.
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Wear model of material couple at high temperatures
Rychlý, David ; Adam, Ondřej (referee) ; Němec, Karel (advisor)
Hlavním cílem práce bylo vytvořit model opotřebení materiálové dvojice za vysokých teplot pro predikci opotřebení kinematického mechanismu na turbodmychadle. Predikce opotřebení je komplexní proces, kterého se účastní mnoho chemických, fyzikálních a mechanických jevů, a proto není jednoduché jej analyticky počítat. Tato práce se vydává naproti tomuto problému pomocí empirických vztahů z literatury a aplikace principů a algoritmů strojového učení (machine learning) postaveného na datech z experimentu. Empirické vztahy i metody strojového učení jsou v práci podrobeny důkladné rešerši a aplikovány na dostupná data z firmy Garrett Motion. Práce kriticky hodnotí vhodnost vybraného empirického vztahu I.G.Goryachevy pro adhezivní opotřebení jako primárního mechanismu opotřebení a variuje koeficienty pro výzkum využití rovnice. Na data jsou aplikovány algoritmy strojového učení a je prezentována architektura nejlepšího modelu – Support Vector Regression – spolu s metrikami, analýzou důležitosti vlastností (feature importance) a optimálním rozdělení datasetu pro trénink a testování. Závěrem práce doporučuje směry dalšího výzkumu a způsoby, jak zlepšit proces modelování pro tento konkrétní problém.
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Point Pleasant bridge collapse - casual analysis of the accident
Jagoš, Jiří ; Němec, Karel (referee) ; Válka, Libor (advisor)
The bachelor thesis is focused on the analysis of the causes of the accident of the Silver Bridge, which occurred in 1967, forty years since the introduction of the bridge to the traffic. In the work are discussed in detail all possible causes of the collapse of the bridge on the basis information and facts mentioned both directly in the inquiry reports of committees, as well as in documents and literary sources, dealing with material analysis of the structural nodes of the wrecked bridge. The work carried out critical analysis of the available and relevant information about the crash. The bachelor thesis outlines also the possible causes of the fall and collapse of the bridge from structural point of view and from terms of the material.
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Heat Treatment of Forged Axles
Kaizar, Libor ; Němec, Karel (referee) ; Molliková, Eva (advisor)
This thesis presents a production and heat treatment of forged axles. Additionally, there is the supplier selection procedures for the production of steel axles, mechanical and chemical tests, methods of preservation and packaging of axles. All procedures and technologies that are listed in this work are used in Bonatrans Group Inc., which is in production and processing of axles one of the largest companies in the world.
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Nickel alloys in aerospace
Šprincl, Jan ; Nopová, Klára (referee) ; Němec, Karel (advisor)
The aerospace industry is one of the fastest growing industries today. Increasing demands on the efficiency and fuel consumption of jet engines can be met, among other things, by using higher quality materials, which clearly include nickel-based superalloys, which can meet these demands. This work provides an overview of these materials: both the building block of the whole structure - nickel, superalloys in general, and especially those nickel-based. It deals with the composition of the microstructure formed by the austenitic matrix ( phases) most often cured by carbide or substitution precipitates, unique mechanical properties, but also the influence of high temperatures and creep on the degradation of these properties. The work also includes a comparison of selected superalloys from different perspectives, especially according to the type of particles that cure the matrix or the effect of loading on the superalloy in the presence of thermal oxidation environment. Depending on the area of application, these materials are predestined for further future development and improvement, because their unique properties in areas with extreme conditions are irreplaceable for the time being.
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Fatigue Properties of Stainless Austenitic Steel
Sedlák, Martin ; Němec, Karel (referee) ; Věchet, Stanislav (advisor)
Final bachelor thesis „Fatigue characteristics of anti-corrosion austenitic steels" is aimed at problematic of mechanics and fatigue properties of Chrome-Nickel austenitic steel CSN EN X2CrNiMo 18-14-3. Thesis aim is to pass judgment on influence of stress cycle asymmetry on fatigue characteristics on high cyclic loading on above mentioned steel. Design Haigh and Smith diagrams. Component of the thesis is metallographical and chemical analysis, mathematical values processing obtained from fatigue tests and also determine primary mechanical properties. Further Wohler´s curves are stated at different stress cycle asymmetry. According to mathematical values processing is designed Haigh and Smith diagrams and fatigue index is calculated. From obtained data result that medium stress of cyclic stress, has of principle influence on appreciate fatigue limit of engaged material.
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The Use of the Aluminium Alloy in the Bicycle Industry
Hudec, Jiří ; Liškutín, Petr (referee) ; Liškutín, Petr (referee) ; Němec, Karel (advisor)
Bachelor's thesis deals with the aluminum alloys in the cycling industry. It contains information on the properties of aluminum and its alloys and the distribution of aluminum alloys according to certain criteria. It is discussed in more detail in the work of most alloys in the cycling industry - Al-Cu-Mg, Al-Mg-Si, Al-Mg-Zn and Al-Zn-Mg-Cu with examples, for which components are suitable alloys. Everything is accompanied by images in the enclosure at the end of work.
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