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Mechanical properties of a novel magnesium WN43 alloy prepared by spark plasma sintering
Greš, Adam ; Knapek, Michal (advisor) ; Dobroň, Patrik (referee)
Title: Mechanical properties of a novel magnesium WN43 alloy prepared by spark plasma sintering Author: Adam Greš Department: Department of Physics of Materials Supervisor: RNDr. Michal Knapek, Ph.D., Department of Physics of Materials Abstract: Properties such as low modulus of elasticity, low toxicity, and biode- gradability make magnesium alloys interesting candidates for medical applicati- ons. To avoid potentially harmful effects of rare earth mischmetal present in the commercial WE43 alloys, it has been replaced in this study with pure neody- mium, which exhibits lower toxicity. To achieve high control over the material microstructure, it was prepared using the spark plasma sintering technique. This study focuses on exploring the mechanical properties of the novel WN43 alloy using compression and tensile testing accompanied by the acoustic emission tech- nique. Ultimate compressive strength and ductility were observed to improve significantly with higher sintering temperatures. In order to obtain better insi- ghts into microscopic aspects of the deformation mechanisms, EBSD images of the samples were taken at multiple points during deformation. It was shown that around the yield point twin nucleation produces strong acoustic emission signal, while later stages of deformation are mostly accommodated by...
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Mechanical and thermophysical properties of illite-based ceramic materials.
Kušnír, Jakub ; Knapek, Michal (advisor) ; Chmelík, František (referee)
Title: Mechanical and thermophysical properties of illite-based ceramic materials. Author: Jakub Kušnír Department: Department of Physics of Materials Supervisor: RNDr. Michal Knapek, Ph.D, Department of Physics of Materials Abstract: This work examines high purity illite-based ceramic material (illite) with varying porosity, illite with fly-ash addition and textured illite- and kaolin-based ceramics. Investigated illitic clay originated from the Tokaj region in Hungary and contained 84 wt.% of illite. Kaolinitic clay (Sedlecký Kaolin Inc.) contained 88-94 wt.% of kaolinite. Samples were prepared using different heating regimes based on the type of material, with maximum firing temperature of 1100 řC. The porosity was controlled by adding charcoal powder to the green body before firing. Fly-ash waste from the combustion of powdered oil shale from Estonia was used as another additive. The microstructure of samples was analyzed by scanning electron microscopy. Mechanical properties were studied by compression tests with concurrent application of advanced investigation methods: Acoustic emission (AE) and Digital image correlation. By means of thermal analyses and AE we also investigated the frost resistance of samples with porosity created by charcoal combustion. Keywords: illite; kaolinite; ceramics;...
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Study of cooperative dislocation phenomena in solids by the acoustic emission technique
Knapek, Michal ; Chmelík, František (advisor) ; Haušild, Petr (referee) ; Landa, Michal (referee)
Title: Study of cooperative dislocation phenomena in solids by the acoustic emis- sion technique Author: Michal KNAPEK Department: Department of Physics of Materials Supervisor: doc. RNDr. František Chmelík, CSc., Department of Physics of Materials Abstract: Plastic deformation of micron-scale crystalline materials differs con- siderably from bulk specimens, as it is characterized by random strain bursts. Three categories of metallic samples were investigated in this thesis: micron- scale copper micropillars with varied geometries, submillimeter-scale aluminum microwires, and aluminum and aluminum-magnesium salt-replicated foams. Very precise fabrication methods and sensitive measurement set-ups consisting of uni- axial compression and tensile tests with concurrent acoustic emission (AE) record- ing were developed. These fine methods allowed for investigations of effects re- lated to plastic deformation at micrometer scales, i.e. the dislocation dynamics associated with the stress drops. Size effects in plastic deformation, as well as clear correlations between the stress drops and the AE events, were found in mi- crosamples, confirming that dislocation avalanches are indeed responsible for the stochastic character of deformation processes also at microscales. Open-cell pure aluminum and aluminum-magnesium...
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Study of cooperative dislocation phenomena in solids by the acoustic emission technique
Knapek, Michal ; Chmelík, František (advisor)
Title: Study of cooperative dislocation phenomena in solids by the acoustic emis- sion technique Author: Michal KNAPEK Department: Department of Physics of Materials Supervisor: doc. RNDr. František Chmelík, CSc., Department of Physics of Materials Abstract: Plastic deformation of micron-scale crystalline materials differs con- siderably from bulk specimens, as it is characterized by random strain bursts. Three categories of metallic samples were investigated in this thesis: micron- scale copper micropillars with varied geometries, submillimeter-scale aluminum microwires, and aluminum and aluminum-magnesium salt-replicated foams. Very precise fabrication methods and sensitive measurement set-ups consisting of uni- axial compression and tensile tests with concurrent acoustic emission (AE) record- ing were developed. These fine methods allowed for investigations of effects re- lated to plastic deformation at micrometer scales, i.e. the dislocation dynamics associated with the stress drops. Size effects in plastic deformation, as well as clear correlations between the stress drops and the AE events, were found in mi- crosamples, confirming that dislocation avalanches are indeed responsible for the stochastic character of deformation processes also at microscales. Open-cell pure aluminum and aluminum-magnesium...
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The Suggestion Small Water Resources
Knápek, Michal ; Mastný, Petr (referee) ; Matoušek, Antonín (advisor)
This Bachelor’s paper deals with design of a micro hydro power plant. First, a suitable location for the plant is chosen. Second, technology for the plant, along with technical equipment and enginery, is proposed. Third, electrical part of the project, including power feeding into the grid, is proposed. Last, economical projection of costs and benefits of the plant is calculated.
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The assessment of advantages of construction of large hydroelectric power plants in the area of Cukrova bouda, district Sumperk
Knápek, Michal ; Kopřiva,, Miroslav (referee) ; Mastný, Petr (advisor)
The subject matter of the master´s thesis is, in particular, an evaluation of the advantageousness of the construction of a pumped-storage hydroelectric power station in the vicinity of Cukrová Bouda. In the master´s thesis introduction the utilisation of pumped-storage hydroelectric power stations in providing reserve power generation to the operator of a power transmission system is discussed. The thesis then focuses on a technical design solution where two alternatives are drawn up for which the nominal parameters of individual designs for a pumped-storage hydroelectric power station are specified. The following part deals with the impact of the structure and the plant’s subsequent operation on the environment. A further key part is the determination of investment and subsequent operating costs and an evaluation of the plant according to economic pointers. The final part of the master´s thesis contains a SWOT analysis and an assumed programme of works for the plant’s preparation and actual construction. The conclusion contains an overall evaluation.
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Design of Home Theater
Knápek, Michal ; Buganská, Tamara (referee) ; Křenek, Ladislav (advisor)
The main aim of my bachelor´s thesis is to find new approaches and new ergonomic, technical and esthetic solutions which satisfy the latest requirements for domestic devices of today. The result should be a design that is modern in appearance and technology should also show a new direction for the design of home theater could take. Another aim is also to fulfill psychological and social function and in order to appeal more to the public and suspended to its beauty.
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