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Production concept of sink
Bahula, Jan ; Jopek, Miroslav (referee) ; Císařová, Michaela (advisor)
The thesis presents a design for manufacturing a rotary kitchen sink made of a stainless austenitic steel 17 240 with a thickness of 0.8 mm with a production series of 20 000 pieces per year. Based on the analysis of manufacturing variants and necessary calculations, deep drawing without a reduction in the thickness was selected to three operations including calibration. A hydraulic press PO 250 from Dieffenbacher was chosen based on the required forces and available rams. The drawing process was checked using numerical simulations and tools were designed for each operation using a drawing ram, a bottom blank holder, and an upper ejector. In the design of drawing tools, normalised components or easily manufacturable parts were preferred.
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Improving the internal quality of aluminum alloy castings by the optimization of foundry technology
Mátl, Vojtěch ; Krutiš, Vladimír (referee) ; Kaňa, Václav (advisor)
This master’s thesis deals with the topic of improving the internal quality of aluminium alloy castings using foundry technology optimization. Theoretical part of this thesis consists of five chapters. These chapters deal with topics of internal defects in castings, solidification of aluminium alloys, numerical simulations in foundry, feeding and use of chills. The second part of this thesis is experimental. It focuses on defect analysis of investigated castings, casting technology simulation and suggestions for its improvement, with consideration for liquid metal utilization.
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Proudění tekutiny v okolí překážky kruhového průřezu
BELOV, Sofya
This bachelor thesis deals with the issue of fluid flow around an obstacle of a circular cross-section, including the phenomenon called Kármán vortex street. Numerical code Lare2d is used for numerical simulations of fluid flow at various Reynolds numbers and extending the issue to magnetic field environment.
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NVH of electric vehicles
Dufek, Martin ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
There is no internal combustion engine in electric cars and although this is a positive shift in development, it presents new challenges in terms of NVH sources. In these days electric cars seem to be the future of the automotive industry so it is necessary to pay attention to it. In the first part the work is focused on the distribution and description of NVH sources, comparison of their importance in the electric car compared to a car with an internal combustion engine and proposing a possible solution for their damping. The second part of the work is then focused on the importance and implementation of numerical simulations and technical experiments for individual parts of EV used in their development nowadays.
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Modelling electron energy-loss spectra of vanadium dioxide nanostructures
Kabát, Jiří ; Křápek, Vlastimil (referee) ; Konečná, Andrea (advisor)
This thesis concerns the characterization of optical modes in vanadium dioxide (VO2) nanostructures, mainly by simulating numerically electron energy loss spectroscopy (EELS) intensity. Among the studied optical modes, there are plasmons, phonons and Mie-type resonances, for which we performed a literature review. VO2 undergoes a phase transition when reaching a temperature of about 67 °C from the insulating phase to the metallic phase. This phase transition is connected to significant changes in optical properties, which offer potential uses in nanophotonics. The main part of the thesis is devoted to numerical simulations, which were firstly performed for thin VO2 slabs and then for VO2 nanoparticles. In simulations of VO2 nanoparticles in the metallic phase, we observed electron energy losses caused by plasmons and localized surface plasmons, which were then characterized and imaged by spacedependent EELS maps. In nanoparticles in the insulating phase, losses caused by phonon excitations and material absorption were observed. A new kind of loss contribution was observed for some geometries, potentially related to the Mie-type resonances.
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Spectral analysis of the B[e] star FS CMa
Kříček, Radek ; Korčáková, Daniela (advisor) ; Mayer, Pavel (referee)
The thesis is dealing with spectral analysis of the B[e] star FS CMa, a prototype of FS CMa stars group. These objects are characterized by huge amount of matter in sourrounding shell which origin is not explained for many years. However, solving this issue could enrich stellar astrophysics by enhanced stellar evolution models. The goal of this thesis is to improve our understanding of FS CMa. We described spectral variability on various time scales and simulated spectra for different forms of the system in HDUST code. On the basis of new obtained spectra we confirmed long-term changes in variability of some spectral features and rapid variability of some spectral lines. We gained an estimate of the gas density. The simulations showed that spectral type of FS CMa is not certain and that the star could be surrounded by extended disk, many stellar radii wide. 1
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Thermal Convection in Terrestrial Planetary Mantles
Benešová, Nina ; Čížková, Hana (advisor) ; Hejda, Pavel (referee) ; Šrámek, Ondřej (referee)
In this thesis, we present results of a numerical modelling study focused on the thermal evolution of the Earth and terrestrial planets. We focus particularly on two problems: I) constraining the internal structure of Venus and Mercury using their geoid and surface topography data and II) evaluating the effects of a rhe- ologically distinct post-perovskite on the secular cooling of the Earth. In part I, we performed simulations in a broad group of models of the Venusian man- tle, characterised by different rheological descriptions, and we compared spectra of their geoid and their surface topography with the observed quantities. Our analysis suggested that the geoid and the surface topography of Venus are con- sistent with a radially symmetric viscosity model with a strong 200 km thick lithosphere, without an asthenosphere and with a gradual viscosity increase in the underlying mantle. In the case of Mercury, none of our models was able to predict observed data, thus suggesting other than a dynamic origin of observed geoid and topography. In part II, we investigated style of Earth's mantle con- vection and its long-term evolution in the models that take into account a weak post-perovskite. We conclude that the presence of the weak post-perovskite en- hances the core cooling. This effect is comparable in...
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Seismic Site Effects (Data Analysis and Modelling)
Caserta, Arrigo ; Zahradník, Jiří (advisor) ; Růžek, Bohuslav (referee) ; Burjánek, Jan (referee)
A comprehensive study of the soil shaking under the seismic wave-field ex- citation is presented. It includes theoretical, geological, geotechnical, data analysis and numerical simulations aspects. The aim is to quantify the main parameters allowing the estimate of the soil shaking in urban areas for better mitigating seismic risk due to future earthquakes. The city of Rome has been chosen as a case study because of its high density of popula- tion and large concentration of historical monuments with high earthquake vulnerability. This study improves significantly the knowledge concerning the detailed near-surface geology of the chosen study area of Rome, ful- fills the absence both of knowledge concerning its geotechnical properties and earthquake data recordings in the city. Among others, it allows for a better explanation of the spatial damage pattern observed in the city due to earthquakes in the past. The main innovations include the construction and long-term operation a seismic array in the city, analysis of the natural seismic noise, and instrumental recordings of the 2009 L'Aquila earthquake sequence. The 3D array (including a borehole sensor at 70-m depth) is the first one in Italy planned, realized and operated within an urban area, and the first one that recorded a significant earthquake in...
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Numerical support for description of behavior of cement based composite during fatigue test
Holušová, Táňa ; Padevět,, Pavel (referee) ; PhD, Ladislav Řoutil, (referee) ; Seitl, Stanislav (advisor)
The presented dissertation thesis is focused on analysis of alternative test method for determination of mechanical parameters of cement based composites. A disk shaped specimen with diameter 150 mm, thickness 60 mm was analysed and its modification for use on compact tension test (CT). Such a test is hereinafter referred to as modified compact tension (shortly MCT or MDCT)). This test configuration was chosen for testing the static and fatigue properties of cement based composites precisely because of its traditional use for fatigue testing of metallic materials. Specimens with a different cross-sections can also be used for MCT, but the work is exclusively focused on circular specimen, for example because it could be easily cut from drill core taken directly from the existing structure, on which the properties are more relevant to the age of the used concrete of the controlled structure. The modified compact tension test was firstly calibrated by numerical simulations involved the tuning of the shape of the numerical model and used material models of concrete and steel. Then the laboratory testing of modified compact tension on several levels were performed. The adequacy of the numerical model was verified against the pilot laboratory testing of the MCT test. Furthermore, the comparison of the modified compact tension test and its suitability for determining of fracture mechanical parameters of cement based composites with the three point bending test, which is the standardized test configuration for these purposes was performed. Another laboratory testing was focused of determining of fracture mechanical parameters of concrete mixture classified in strength class C30/37 and the pilot study of fatigue parameters of the same strength class of the concrete mix. The work was also presented numerical simulations of the push-out test, focused on the connection of concrete and steel with epoxy adhesive.
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Identification of rate type fluids suitable for modeling geomaterials
Tůma, Karel
In the present thesis we study and compare different viscoelastic rate-type fluid models capable of describing response of geomaterials such as asphalt. Using new thermodynamic approach proposed by Rajagopal and Srinivasa (2000) we derive several classes of non-linear viscoelastic models that generalize standard Oldroyd-B and Burgers models. We show that the new models achieve better results in fitting experimental data with asphalt than the previously considered models (Oldroyd-B, Burgers, Rajagopal and Srinivasa (2000)). In particular they are able to capture the behavior of asphalt observed recently in experiments (torque overshoot and two relaxation mechanisms), which is not possible to describe by the other models. Using both the standard and the newly derived models we compute full simulations of viscoelastic flow with the finite element method in fixed domains and incorporating the Arbitrary Lagrangian-Eulerian description also in deforming domains. For example, we study rolling of asphalt or creation of ruts in the road with the real material parameters obtained by fitting the experiments. Powered by TCPDF (www.tcpdf.org)
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