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Basic Mechanism of Fatigue and Combined Fatigue/Creep Damage of Ni-based Superalloys MAR-M 247 and IN 713LC
Horník, Vít ; Kohout, Jan (referee) ; Pantělejev, Libor (referee) ; Kunz, Ludvík (advisor)
The thesis is focused on clarifying fatigue damage mechanisms and fatigue-creep damage mechanisms of MAR-M 247 and IN 713LC polycrystalline Ni-based superalloys. This thesis begins with basic information about nickel-based superalloys and their microstructure, followed by a description of fatigue and creep mechanisms and their mutual interaction. The next part contains experimentally obtained results describing the behavior of MAR-M 247 and IN 713LC superalloys under various sets of conditions. Three testing temperatures - 800, 900 and 950 °C were used for the measurement of fatigue properties under symmetrical loading cycle, because in the temperature range 800 – 950 °C, the mechanism of fatigue crack propagation of both superalloys should change from the originally crystallographic at "lower" temperatures (800 °C) to non-crystallographic at "higher" temperatures (950 °C). In addition the effect of processing technology on fatigue properties was studied on the superalloy IN 713LC. High-frequency cyclic loading (about 120 Hz) with high mean stress at elevated temperatures was applied to induce fatigue-creep interaction. The combined fatigue-creep loading was performed on the IN 713LC superalloy at 800 °C and on the MAR-M 247 superalloy at 900 °C.
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Fatigue properties of titanium alloys
Horník, Vít ; Němec, Karel (referee) ; Věchet, Stanislav (advisor)
This bachelor thesis is concerned with fatigue properties of titanium alloys. The introductory part deals with basic information about titanium, its production, distribution of titanium alloys and their heat-treating. Next part then describes basic process of fatigue loading with the focus on the high-cycle fatigue stress and its application on some titanium alloys. The final part of the thesis includes optical and fractograph pictures.
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Analysis of the influence of temperature cycles on the elimination of recast layer on materials used in aerospace
Slavíková, Barbora ; Martin,, Grepl (referee) ; Horník, Vít (advisor)
This bachelor thesis is dealing with the analysis of the influence of temperature cycles on the elimination of recast layer on materials used in aerospace. This thesis was created in cooperation with Honeywell Aerospace Company in Olomouc. The aim of this work was to prepare the study about influence of the brazing heat cycle on recast layer removing which was caused by laser cutting process. In first part of this bachelor thesis the unconventional machining methods, materials and related brazing processes used in Honeywell Aerospace Olomouc were described. Second part of the thesis consists of experimental measurement of the recast layer provided on a test specimens including their evaluation and interpretation of the results. The conclusions of this bachelor thesis will be used as future reference for next technological research in Honeywell Aerospace Company in Olomouc.
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Control of excitation of synchronous generator
Horník, Vincenc ; Červinka, Dalibor (referee) ; Huták, Petr (advisor)
The main focus of the work is to create the optimal design of the reconstruction of synchronous generator excitation system of small hydro power plants with regard to the economical and technical performance, description of synchronous generator excitation, possible technical solutions to the reconstruction of excitation systems and their driving.
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Initiation and development of cyclic damage in steel for the energy industry
Horník, Vít ; Mazal, Pavel (referee) ; Věchet, Stanislav (advisor)
The main content of this master's thesis is a determination of the fatigue properties by using non-destructive testing methods – the acoustic emission technique and the X-ray diffraction. The reactor steel, that is named GOST 15Ch2NMFA, is used as a model material and is used to manufacture VVER-1000 reactor pressure vessels. The supplied material was made of two different steel melting, designated as H and S. For the basic measurement of the fatigue properties the stress-cycle asymmetry R = -1 was used. Some of the samples were used for approximate determination of the fatigue strength stress-cycle asymmetry R = 0. During the loading process the resonance frequency of the loading machine and acoustic emission signals were recorded. The changes in microstructure were estimated from the record of acoustic emissions during the whole fatigue life. The change of the microstructure was experimentally observed by X-ray diffraction analysis. The mechanism of the fatigue can be described by the observation of the microstructural processes as well as the relevant bifurcation with sufficient sensitivity. The results of the used methods indicate a decay and re-growth of mosaic blocks during the whole loading process. Therefore, it is important to find a correlation of these two non-destructive methods, or to use other non-destructive testing methods in the future.
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Thermomechanical fatigue of austenitic stainless steels
Dobeš, Ondřej ; Petráš, Roman (referee) ; Horník, Vít (advisor)
The aim of this bachelor thesis was to study the influence of termomechanical fatigue with dwells in loading cycles on material response as well as damage mechanism. Austenitic stainless steel Sanicro 25 was subjected to in-phase and out-of-phase thermomechanical fatigue (TMF) loading conditions with different amplitudes of mechanical strain in the temperature range 250 to 700 °C. The mechanism of the damage was investigated by means of scanning electron microscope equipped with focused ion beam (FIB) and electron backscatter diffraction (EBSD). Different mechanisms of the fatigue crack initiation were observed in in-phase and out-of-phase TMF cyclic loading. The effect of the type of loading on the damage mechanism and fatigue life is discussed.
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Computer at home and at school with regard to the risks to the childs personal development
Knapová, Jana ; Krykorková, Hana (advisor) ; Horník, Vlastimil (referee)
This thesis on "Computer at home and at school, having regard to the risks to the child's personality development", discusses how to use computers in school, especially in the education, home and leisure of the child. Work emphasizes the risks resulting from improper use of information and communication technology (especially computers and the Internet) and offers solutions to minimize these risks. The aim is to acquaint the reader with the emerging phenomena due to using computers, such as the already extensive social networking, cyberbullying and "addiction" emerging on the Internet and computer games.
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Alternatives of modern information technologies used in education
Horník, Vlastimil ; Koťa, Jaroslav (advisor) ; Vališová, Alena (referee)
The intent of this thesis is to chart educational technology issues. In the theoretic part I'm engaged in universal questions related to school modemizing, teachertechnique relations and a teacher's role in a leaming process supported by an educational technology. In addition to a traditional educational technology and a literature about it, I'm interested in a modem educational technology used along with computers. Except a summary ofthis technology I'm thinking about its use. In the practical part I worked out a case study that charts the process of selected secondary school modemizing. For this purpose I have chosen a school I'm teaching at. It has provided me to get down more in a process of the school modemizing. Even if this part is intended on one concrete school I suppose that problems which have appeared there are similar as in other schools. An outcome of this thesis is a summary of key issues related to a process of modemizing and an indication of next development in this sector.
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Comparison of mortality trends in Central Europe and Baltic countries from 1970 to the present
Horník, Vojtěch ; Hulíková Tesárková, Klára (advisor) ; Burcin, Boris (referee)
Comparison of mortality trends in Central Europe and Baltic countries from 1970 to the present Abstract The aim of this thesis is to assess the most important mortality trends development in countries of Central Europe and Baltic region between 1970 and 2009. The measures used involve life expectancy at birth and life expectancy at the age of 65; besides of this, the age-specific contributions to life expectancy changes are computed according to the method of R. Pressat. The convergence and divergence tendencies among the analyzed countries and between the two regions are evaluated in this thesis as well. Main findings are, on one hand, that mortality trends are relatively similar within each of the regions. When comparing regions between each other, however, significant differences, mostly in the period between mid-1980s and mid-1990s, arise, they are attributed mostly to the influence of mortality crisis in Baltic region after the Soviet Union dissolution. Even though after 1994 mortality development was favourable in Baltic countries, they did not reach mortality level of Central Europe until 2009. Keywords: mortality, Central Europe, Baltic countries, life expectancy, decomposition, convergence, divergence
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