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Chemical-heat treatment of steels
Rozum, Jakub ; Pokorný, Zdeněk (referee) ; Sedlák, Josef (advisor)
This thesis deals with study of surface layers of low-carbon steels formed by chemical-heat treatment. The first three chapters consist of theoretical part of the thesis, there are explained basic physical principles of these technologies and described individual types, the third chapter deals with the application of chemical-heat treated low-carbon steels in mechanical engineering. The experimental part of thesis deals with analysis of surface layers of two low-carbon steels formed using plasma nitrocarburizing and gas nitrocarburizing. The properties of these layers are evaluated based on the results of mechanical tests (hardness tests) and observation of microstructure. The thesis is completed by discussion, where the achieved results are evaluated.
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Multiphase Ti-Ni layer on titanium substrate by local alloying
Husťák, Miroslav ; Havlík, Petr (referee) ; Jan, Vít (advisor)
The theory section of this thesis is to describe properties and utilisation of titanium and titanium alloys as well as to deal with various methods of surface treatment and means of alloying a titanium surface layer with nickel. The experimental chapter of this thesis is to describe the creation of a hard surface layer on titanium substrate. In order to achieve a hard surface layer, a layer of nickel was electrodeposited on substrate made of commercially pure ASTM Grade 2 titanium which was subsequently melted with the help of an electron beam. A layer with changed chemical composition and microstructure was created by applying the aforementioned method on the titanium surface. In order to achieve a homogeneous microstructure in the surface layer, several samples with the surface layer were prepared by utilising different parameters of the electron beam. The samples were later tested for their microstructural homogeneity, chemical composition, and hardness.
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Computational analysis of working roll surface layers in hot rolling
Luks, Tomáš ; Hajduk,, Daniel (referee) ; Pohanka, Michal (advisor)
This thesis is dealing with an analysis of thermal and mechanical loads on a work-roll. First, hot rolling focused on work-roll is described in general. A theoretical analysis of roll loads and the mechanisms affecting roll durability are presented here. The thesis is concentrated on creation of a model in FEM program ANSYS. The final model is loaded with different rolling schemes and monitored stresses in a surface layer. The parameters obtained from the measurements performed in a rolling mill are applied as boundary conditions within the model.
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Study of bioceramic materials on the base of calcium phosphates
Kolář, Martin ; Maca, Karel (referee) ; Cihlář, Jaroslav (advisor)
The literature search on the topic of Bioceramic materials focused in layered materials based on calcium phosphates was written up. Based on knowledge obtained, experiments of preparation of calcium phosphates layered materials based on calcium phosphates by spin-coating method focused in optimalization of layer application conditions were designed and carried out. Experiments of preparation of hydroxyapatite bulk ceramics by uniaxial pressing followed by heat treatment were also performed. Prepared layered and bulk ceramics were characterized from bioactivity point of view by testing of their interaction with simulated body fluid.
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The limits of movement and quantification of bedload amount for gravel-bed rivers
Roušar, Ladislav ; Matoušek, Václav (referee) ; Tůma, Antonín (referee) ; Veselý, Jaroslav (advisor)
Doctoral thesis in detail and comprehensively deals with mechanic of incipient bedload motion for gravel-bed rivers. This study based on theoretical knowledge, experimental researches, numerical models and field survey extends present knowledge concerning with incipient bedload motion and sediment transport at small relative height and hydraulically rough surface bed for turbulent unaerated free surface flow. Incipient bedload motion and sediment transport have been determined for homogeneous and inhomogeneous bed materials. For homogeneous bed material the velocity profiles have been described by different methods in near the bed. Further, hydraulic flow resistance has been evaluated. In the case of inhomogeneous bed material, static armouring and influence of surface layer sorting on hydraulic roughness have been investigated. The correctness of obtained knowledge has been confirmed on the object of nature-inspired river widening. Results shown, among others, that incipient bedload motion does not depend on relative height or final armouring of surface layer to what extend hydraulic roughness is influenced.
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Change in the durability of concrete made of recycled concrete by alternative addition of ceramic admixtures
Stavař, Tomáš ; Hoffmann, Oldřich (referee) ; Stehlík, Michal (advisor)
The master thesis dealing with problematic about durability of concrete, with use of recycled concrete and addition of silica additions. Predominant for resistance of concrete constructions is surface layer, through which aggressive gasses and liquids penetrate from surrounding environment. The most important indicator of concrete durability is ability of surface layer transmissions of aggressive substants. In experimental part will be defined the actual state of surface layer by normal testing methods. The transmissions of surface layer will be tested on concrete cubes. Tests for transmissions of air (method TORRENT), of water (method ISAT), of acid gases (dept of carbonation by quick test in 98% CO2) will be carried out and also strength tests. Assessment of positive or negative influence of additions and amount of cement on durability and mechanical properties of concrete will be discussed in conclusion.
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Chemical-heat treatment of steels
Rozum, Jakub ; Pokorný, Zdeněk (referee) ; Sedlák, Josef (advisor)
This thesis deals with study of surface layers of low-carbon steels formed by chemical-heat treatment. The first three chapters consist of theoretical part of the thesis, there are explained basic physical principles of these technologies and described individual types, the third chapter deals with the application of chemical-heat treated low-carbon steels in mechanical engineering. The experimental part of thesis deals with analysis of surface layers of two low-carbon steels formed using plasma nitrocarburizing and gas nitrocarburizing. The properties of these layers are evaluated based on the results of mechanical tests (hardness tests) and observation of microstructure. The thesis is completed by discussion, where the achieved results are evaluated.
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Multiphase Ti-Ni layer on titanium substrate by local alloying
Husťák, Miroslav ; Havlík, Petr (referee) ; Jan, Vít (advisor)
The theory section of this thesis is to describe properties and utilisation of titanium and titanium alloys as well as to deal with various methods of surface treatment and means of alloying a titanium surface layer with nickel. The experimental chapter of this thesis is to describe the creation of a hard surface layer on titanium substrate. In order to achieve a hard surface layer, a layer of nickel was electrodeposited on substrate made of commercially pure ASTM Grade 2 titanium which was subsequently melted with the help of an electron beam. A layer with changed chemical composition and microstructure was created by applying the aforementioned method on the titanium surface. In order to achieve a homogeneous microstructure in the surface layer, several samples with the surface layer were prepared by utilising different parameters of the electron beam. The samples were later tested for their microstructural homogeneity, chemical composition, and hardness.
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Thermal regime of moraine cover in the Adygene valley, Kyrgyz Range
Martinásková, Daša ; Engel, Zbyněk (advisor) ; Uxa, Tomáš (referee)
The focus of this bachelor thesis is the thermal regime of the morain covering in the valley of river Adygine in Kyrgyz Range area in the northern Tien-Shan. The intention of this thesis is to evaluate the temperature measurements from the glacis zone of the Adygine glacier and to explicate the results with regards to the continuance of recent permanent snow line and permafrost area. In the area of interest, with altitude 3498 to 3659 m, two air temperature sensor and five thermistors with MINIKIN dataloggers were installed. The thermistors measure temperature in 15 and 30 cm depths below the surface of glacial accumulations. The surface layer of morains melts annually for three or five months, mean annuall ground temperature did not drop below -2řC and area of measurements is distinguished with weak freeze-thaw activity. The mean annual air temperature in year 2011 was -4,5 in 3653 m and -6,1řC in 3913 m altitude respectively. The comparsion of measured data with publicated average permafrost temperature data in nearby ranges of Tan-San mountains suggests, that area of interest is located in discontinuous mountain permafrost area. Zero isothermic line is located in approximately 2900m altitude. This is lower than the mountain permafrost level and so the base of glaciál forefront can be denoted as...
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