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HEAT – MECHANICAL DEGRADATION OF SURFACES AT THE HIGH TEMPERATURES
Zahradník, Radek ; Hajduk, Daniel (referee) ; Čecho, Ladislav (referee) ; Toman,, Zdeněk (referee) ; Raudenský, Miroslav (advisor)
The Ph.D. thesis is focused on a surface degradation mechanisms under combined heat and mechanical load. The objects of examination are work rolls from hot rolling mill which suffer such a load. In first chapter, the hot rolling process, the design, the manufacturing process and present materials of work rolls are described. The state-of-the-art study of work roll surface degradation mechanisms – wear, oxidation, thermal and contact fatigue are described in the second chapter. The characterization, the formation, the mechanisms of progression and the effects of each surface degradation mechanism is described step by step. The state-of-the-art study of analytical and numerical models which are related to hot rolling process is described in third chapter together with their limitations and flaws. The next chapters contain design of an analytical, an optimized macroscopic and a microscopic model for study of the work roll stress state. The macroscopic and the microscopic model is based on finite element method and they are implemented in ANSYS Programming Design Language. The models are used to process several case study which are based on previous experimental work of the Heat transfer and fluid flow laboratory. The results from case studies specify and expand the knowledge of work roll stress state. The results show the portion of each loading factor on the whole stress state. In addition, time and depth depended distribution of stress state is presented. The results from macrosferic model illustrate the cause of spalling and a rupture of the work roll. The results from the microsferic model show the cause of creation of the to-surface-parallel cracks within carbides of high chromium irons. Last chapter summarized of all results gathered from case studies together with the goals for further research definition. The necessary steps for further cognition are stated. The thesis contains a large set of appendixes with deeper discussion of several related topics. These appendixes represent the one third of whole the thesis.
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Proposal to revitalize the banks of the flooded Hulín sandstones - section 2
Čuda, Ondřej ; Pelikán,, Petr (referee) ; Šlezingr, Miloslav (advisor)
The subject of this bachelor’s thesis is to prevent the retreat of the bank line by the proposal of suitable biotechnical stabilization of the banks of the flooded Hulín sandstones on the specified section. Shore abrasion is mainly caused by the starting wind, which results in the formation of waves that subsequently spread the banks. The result of the thesis is the processing of biotechnical stabilization proposals, which are intended to reduce or slow down the retreat of the bank lines.
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Classification and evaluation of rail wear
Nohel, Rostislav ; Frýza, Josef (referee) ; Galas, Radovan (advisor)
This bachelor’s thesis is focused on the wear of rails. In this thesis, the reader will be firstly introduced to the fundamentals such as nomenclature of wheel and rail, adhesion, adhesion coefficient, contact area, slip, traction characteristic and wear. Subsequently, the fundamental types of material wear (adhesive, abrasive and fatigue) will be explained, which occur in the wheel-rail contact. In the next part, the individual rail defects are analysed with respect to locations. The output of the bachelor’s thesis is overview and description of the most common rail defects which are usually caused by fatigue wear.
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Stabilization of the flooded sand pit near Hulín
Patková, Aneta ; Pelikán,, Petr (referee) ; Šlezingr, Miloslav (advisor)
The aim of this bachelor thesis is to assess the current state of the bank damaged by abrasion of the flooded gravel and sand pit in Hulín with the subsequent proposal of suitable biotechnical or biological stabilization and hydrological calculations to determine the prognosis of the prognosis retreat of the coast. As part of the field survey, photo documentation of abrasive log cabins caused by wind waves and water level fluctuations was taken. Part of the work is also the proposal of a total of six stabilization measures, the construction of which should prevent or slow down the effects of abrasion.
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Slurry surfacing - composition and quality issue
Dostál, Filip ; Koudelka, Tomáš (referee) ; Hýzl, Petr (advisor)
This thesis is focused on slurry surfacing technology, particularly on microsurfacing. The theoretical part describes the differences between the slurry seal and microsurfacing. Ingredients for the production and laying. There are also described their advantages. The practical part presents proposal of mixture and demonstrate that the service of life of the emulsion mixture is closely related to the content of residual binder and composition of microsurface.
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Stabilization of bank
Podola, Martin ; Pelikán, Petr (referee) ; Šlezingr, Miloslav (advisor)
The subject of this bachelor’s thesis is assessment of reservoir banks Bystřička in terms of abrasion. Judgement is focused on two main points on the northeastern bank of the reservoir near the tributary. It is an area near the hotel Beskydská Tatranka. Thesis is finished with design of selected biotechnical measures to slow or stop erosions banks.
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Study on wear of material in contact with MR fluid
Žáček, Jiří ; Vimmr, Jan (referee) ; Kubík, Michal (advisor)
This paper is focused on MR dampers and its critical parts in term of damper`s durability, which seems to be a piston-rod seals, and it should find an ideal material combination of seal and MR fluid for increasing the damper`s life. The tests were conducted in modified pin-on-flat configuration, which was supposed to be more suitable for laboratory testing. There was tested and compared a suitable material for seals, like PTFE, NBR, SBR of polyurethanes. The article is also focused on MR fluids and its contribution to seal`s wear. The impact of particle concentration, wear of MR fluid and effect of modification of MR fluid was tested. It showed up, that the best material for seal is H-PU95FDA. The effect of particle concentration is negligible on seal`s wear, while effect of modification and wear of MR fluids are significantly higher.
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Proposal to revitalize the banks of the flooded Hulín sand pit
Skřížala, Lukáš ; Pelikán,, Petr (referee) ; Šlezingr, Miloslav (advisor)
The master´s thesis deals with the assessment of the state of the shore territory on the Brno reservoir, in the Osada area and subsequently the proposal for shore stabilization. As part of a personal visit to the area of interest, photographic documentation, geodetic focus and subsequent assessment of the current state of the abraded shores were made. Using the geodetic focus and data of water heights on the reservoir provided by the Povodí Moravy, s.p. the most numerous in the reservoir was evaluated in 2007-2017, the coastline retreat and the proposed shore stabilization were determined. There was suggested totaly eight measures were proposed against the further retreat of the shore line, which were incorporated into schemes and visualizations.
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