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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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Coulomb Interactions in Electron Beams
Jánský, Pavel ; Janík,, Ján (referee) ; Kolařík,, Robert (referee) ; Lencová, Bohumila (advisor)
The thesis deals with numerical simulations of a hairpin thermionic electron gun, an electron source of the electron-beam welding machine. Simulations showed that the space charge in the electron gun has a significant influence on the beam current and electron trajectories. Simulation outputs are in a sufficient agreement with the experimental measurements.
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Methods of Space and Spectral Characterization of Light Sources used in Car Industries
Guzej, Michal ; Černý,, Pavel (referee) ; Samek, František (referee) ; Horský, Jaroslav (advisor)
Automotive headlamps work in very variable operating conditions during which the producer have to guarantee their primary function of seeing and being seen. During the development stage of the new headlamps the manufacturers want to eliminate defects which could led to malfunction in operation. The numerical simulations along with the test procedures are appropriate tools for detection of problematic areas. The most appropriate approach is designing of experiment with a view to the subsequent simple implementation of the measured data into numerical simulations software and carefully choosing a measuring method of the monitored physical quantities. The thesis deals with phenomenon of condensation in headlamps, which has a negative effect on the light distribution and their life expectancy. Due to this experimental defog methodology was developed based on evaporation of a specified amount of water into the headlamp and then condensation on the inside surface of the headlamp lens. Pictures are taken during the measurements and the fogged and defogged areas are automatically detected. The results from experiments are used to adjust and verify a numerical model. The next part is devoted to the thermal load of the headlamp components which are mostly heated by waste heat from light sources. This phenomena depends mainly on the type of source, emissivity and thermal conductivity. A methodology of temperature measurement, thermal conductivity measurement, non-stationary method for emissivity determination and spectral characterization of thermal source based on their thermal fluxes to the surroundings has been developed.
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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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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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Numerical simulation of mold filling and casting solidification
Kolda, Vlastimil ; Herman,, Aleš (referee) ; Krutiš, Vladimír (advisor)
The object of this diploma thesis is to analyze, persuant to numerical simulation of current technology of production aluminous casting roller-reck V9X, causes of the rise of cold lap and laminations defects. Consequently, to work up a project of variant solution of the shape of casting so, as to come to elimination mentioned defects. This variant solving will be tested with numerical simulation as well. Fruitfulness of these designed changes will be verified by testing molten of the casting. In terms of solve the problem the simulation of cycling of the mold and subsequently the filling of the casting will be effected. During the analyse of filling of the die the first phase of filling will be effected too.It means the movement of the piston throught the chambre. Simulation of solidification of the casting wont be effected because of the type of the defect.
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Diversion headwork on Smolinka river
Juriga, Jan ; Brázda, Daniel (referee) ; Zachoval, Zbyněk (advisor)
Within the preparation of the dam Vlachovice, it is planned to construct a diversion work on the Smolinka river to ensure the transfer of water from the Smolinka basin to the Vlachovice reservoir. The diversion work is designed by AQUATIS a.s. and is equipped with a sluice gate and a spillway with a crest intake. This thesis deals with the determination of recommendations for the implementation of modifications to the design of the diversion work. Recommendations resulting from the work should lead to reliable functionality of the object both from the point of view of water intake and from the point of view of continuous transport of sediments through the Smolinka river. A two-dimensional numerical model simulating sediment transport and three-dimensional numerical model simulating water flow are used in the thesis to determine recommendations for design modifications. The documents necessary for the creation of the work were provided by company AQUATIS a.s. with the permission of Povodí Moravy, s.p
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Prediction of welding joint distortion by computer simulation.
Vaněk, Mojmír ; Slováček, Marek (referee) ; Daněk, Ladislav (advisor)
In this master’s thesis there are set down dependencies of distortion of T-joints on the size of heat input and welding speed. Dependencies were found for single- and double-fillet welds, for single- and multiple-pass welding. The computer simulations were carried out in programs Visual-Weld and SYSWELD. The size of the melted zones, stress fields, material structure and hardness of the weld specimens were specified. Simulation results were compared with experimentally detected values.
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Production of the distributor by non-convential forming technology
Blažek, Matěj ; Peterková, Eva (referee) ; Jopek, Miroslav (advisor)
The thesis is focused on the evaluation of the possibility of manufacturing a distributor body used for distribution of heat-bearing medium in underfloor heating. For the part, due to the series of 100 000 pieces·year-1, the technology of high-pressure hydrofroming without active action of axial presses is chosen. The original solution with a forming pressure of 58,5 MPa did not lead to success and an optimization was necessary, where the pressure was increased to 158,5 MPa, which also did not lead to success. This was followed by a further optimization consisting of hot forming at 700 °C and a pressure of 158,5 MPa, again with no successful solution. The last possible treatment option of changing the material to 11 321 steel and pressure 134,2 MPa was not successful and the high pressure hydrofroming method with passive action of axial dies is not recommended for industrial practice. The final step was an economic evaluation, where the price per piece was determined to be 133,3 CZK with a 20% margin. Considering that the product is suitable the profit will start to be generated after the production of 140 460 pieces.
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Numerical simulation of oil flow in the gearbox
Činčár, Vojtěch ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
Component design, subsequent functional verification and possible optimization are an integral part of any production process. Based on increasing customer requirements, the aim is to achieve the smallest possible dimensions and the lowest possible price, while maintaining safety. Incorporating both aspects can be achieved using advanced computational approaches, while this work focuses on the area of flow simulation. Specifically, it deals with the analysis of oil flow in a railway vehicle gearbox using computational fluid dynamics or CFD. The flow simulations were performed using ParticleWorks software, which works with the semi-implicit moving particle method MPS, whose suitability was verified by short analysis works. By monitoring the flow in the workspace, the geometry of the gearbox housing was first verified. However, the critical areas are the bearings whose lubrication quality was analysed using a series of computational models that included the service conditions that may occur. In addition to summarizing the overall evaluation, the paper concludes by outlining a possible suggestion for the potential improvement of bearing distribution and lubrication quality.
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