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Numerical simulation of volume changes of selected cementitious composites
Drbušková, Magdaléna ; Veselý,, Václav (referee) ; Keršner, Zbyněk (advisor)
This thesis deals with volume changes of selected cementitious composites. They are divided into two parts, theoretical and practical. The theoretical section describes the volume changes that occur in concrete structures. The practical part is focused primarily on the initial stage of shrinkage specimens of two-component cement composite (cement paste + aggregate) and it´s numerical simulation. For analysis were used SpatiDist and FyDiK 2D computer applications. It was simulating shrinkage of specimens with and without notch to compare. The result is a parametric study which reflects the influence of type and size of grain aggregate and shrinkage degree of cementitious paste.
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Stress-strain analysis of the thin wall structure subjected to impact load
Tatalák, Adam ; Peč, Michal (referee) ; Návrat, Tomáš (advisor)
This master thesis deals with stress-strain analysis of simplified model of the thin wall transformer case subjected to impact load of electrical blast. Electrical blast is replaced by chemical blast (detonation of high explosive). The problem is solved using computational modeling utilizing the Finite Element Method (FEM) and LS-DYNA solver. After the introduction where detonation and shock wave propagation is explained the analytical approach is presented. This approach serves to results verification. In the next chapter is conducted research of applicable methods from which ALE method is chosen. In preliminary study is performed the mesh size analysis that is focused on finding the size of element which is both computational effective and gives accurate results. Next the infulence of input conditions (shape, location and parametres of high explosive, location of detonation point, boundary conditions) on distribution and time progress of pressure is investigated. Then influence of the opening on upper side of the case on overall pressure redistribution and strain and stress of the case is analysed. The stress-strain analysis of the case´s door which are connected to case by various types of contact models is performed as well as stiffness analysis of these types of contact.
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Quantification of hydrodynamic load on overflowed bridge deck using 2D numerical simulation
Pavlíček, Michal ; Hrdlička, Libor (referee) ; Špano, Miroslav (advisor)
The diploma thesis is focused on a quantification of hydrodynamic load of overflowed bridge deck. Solution was pursued by using two–dimensional numerical simulation of open channel flow in vertical plane created in ANSYS 15.0 software (modules: Workbench, Design Modeler, Meshing, Fluent). Values of drag force, lift force, moment, drag coefficient, lift coefficient and moment coefficient is result of computation. Various types of bridge decks were tested in relation to the degree of inundation (inundation ratio) and flow velocity.The thesis provides comparison of numerical simulation with physical experimental testing and result published in accessible resources.
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Effects of Non-Newtonian Lubricants on Surface Roughness in Point Contacts
Ficza, Ildikó ; Kaneta, Motohiro (referee) ; Poll, Gerhard (referee) ; Hartl, Martin (advisor)
Tato dizertační práce je zaměřena na studium deformace nerovnosti uvnitř elastohydrodynamicky mazaného (EHD) kruhového kontaktu. Práce se zabývá studiem přechodu příčné nerovnosti přes kontaktní oblast, která je modelována pomocí numerických metod. Model dále uvažuje nenewtonské chování maziva. Použitý matematický model se skládá z parciální diferenciální rovnice druhého řádu pro řešení tlaku a integro-diferenciální rovnice pro řešení elastických deformací. Pro řešení tohoto modelu je použitá takzvaná multigrid (vícesíťová) metoda. Práce obsahuje popis matematického modelu EHD kontaktu a aplikované numeriké metody. Výsledky simulací jsou porovnány s experimentálně stanovenýma hodnotama tloušťky mazacího filmu. Deformace nerovnosti uvnitř kontaktní oblasti je studována pro různé provozní podmínky (střední rychlost, poměr proklzu) a různá vlastnosti maziva.
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Study of Post-Discharge Processes
Soural, Ivo ; Hrachová, Věra (referee) ; Brablec, Antonín (referee) ; Krčma, František (advisor)
The decaying plasma was studied by the optical emission spectroscopy. DC discharge created at 45 – 200 mA in Pyrex and Quartz tubes in flowing regime was used. The emission of three nitrogen spectral systems (1st and 2nd positive and 1st negative) were studied in time evolution for pressures of 500 – 5 000 Pa at two wall temperatures – ambient and liquid nitrogen (150 K inside the decaying plasma). Results showed that all three nitrogen systems (respectively N2(B, v), N2(C, v) and N2+(B, v) states as their origins) had their population maxima called pink-afterglow in the afterglow part. These maxima decreased with the increase of pressure for all systems, and moved to the later decay time. Maxima increased with discharge current (respectively power) and moved to shorter time. Populations at temperature of 150 K were measured due to the experimental arrangement from 17 ms, only, and thus pink aftergow maximum wasn’t observed (only at 5 000 Pa some maximum was recognized). Populations were smaller at 150 K that populations measured at laboratory temperature at the middle decay time (50-100 ms). At the late time, the populations were higher at lower temperature at lower pressure. Higher shifts (in intensity and decaytime) of pink afterglow maxima were observed in Quartz tube in comparison with their values in Pyrex tube. Besides the populations, rotational temperatures of selected bands of three observed spetral systems (for 1st negative 0-0 band, 1st positive 2-0 band and for 2nd positive 0-2 band) were measured. Rotational temperatures were monitored from presumption that this kind of temperature is equal to temperature of neutral gas (at local thermodynamic equilibrium). Results from 1st negative and 1st positive system showed strong decreasing of rotational temperatures up to about 10 ms at post-discharge begin, then temperatures were constant up to 20 ms of decay time and after that they grew up. Temperatures increased with the increase of current. The part with decreased temperature correlated with pink-afterglow part of post-discharge. Unfortunately, rotational temperatures of 2nd positive system had bad reproducibility and the time profile shape was opposite. Experimental results were compared with numerical kinetic model created by group of prof. Vasco Guerra at Instituto Supetior Técnico in Portugal. Several sets of conditions for simulation at 500 and 1 000 K in active discharge were applicable for the calculation corresponding to the experiment. Comparison of numerical simulation and experimental data done for N2(B) state demonstrated that maxima populations in pink afterglow are depended on the temperature difference between active discharge and post discharge. Maxima populations were supposed in pink afterglow disappeared if the same temperatures in active and post discharges were supposed. Temperature in active discharge is higher at higher apllied power, as it was showed from rotational temperatures observation. The results clearly showed that real temperature profile must be included into the kinetic model.
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Numerical simulation of the ceramic core manufacturing in the investment casting process
Kinc, Marek ; Kováč, Marek (referee) ; Tomek, Ladislav (advisor)
The aim of this diploma thesis is validation of numerical simulation of the ceramic core manufacturing in the investment casting proces. The first part submit the theoretical description of the manufacturing of the ceramic cores and a description of the basic principles of numerical simulations. The second part compares the video recording of filling the wax-ceramic mixture to the die-casting mold and simulation of the same process created in a simulation software Cadmould 3D-F.
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Glazed Balcony as Preheater of Ventilation Air - Parametric Study
Macháček, Pavel ; Janírek, Martin Stanislav (referee) ; Fišer, Jan (advisor)
This thesis deals with the influence of balcony glazing to preheat ventilation air. In the first part there are described the ways of passive use of sun radiation and types of ventilation of flats. THESEUS-FE 4.0 is used as a simulation program, for which heat transfer is described. The second part contains description of flat and selected case simulation, followed by a geometric model and description of boundary conditions. Finnaly is done evaluation of case simulations not only in therms of savings in ventilation, but also for heat loss as a whole.
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Sheet metal drawing and its verification by computer simulation
Něnička, Filip ; Kopřiva, Miloslav (referee) ; Štroner, Marek (advisor)
This thesis engages on the differences between the numerical simulations of sheet metal drawing process performed using AutoForm software from AutoForm Engineering, Swiss company and actual results measured using non-contact measurement system Argus from German GOM company. This work used DC06 material (whose mechanical properties were determined at Technical University of Liberec) for comparison. The calculated results of simulations were compared to measured results of actual plate thickness.
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Defects and properties of heavy castings
Sobotka, Petr ; Carbol, Zdeněk (referee) ; Záděra, Antonín (advisor)
A diploma thesis was objected to a figure analyzing and a figure interpretation of ingot processing. The described figures were obtained from samples which were taking from feeder-heads of ingot of lower ram, produced in Vitkovice Machinery Group. The thesis was focused on ingot solidification and segregation processes which were associated with this procedure. The figures obtained from numeric simulation of ingot solidification in defined places were analyzed using statistic method – linear regression, as well as linear regression was used for evaluation of explored samples, their chemical compositions and mechanical properties. In conclusion all acquired results were summarized.
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Numeric simulation of surfacing turbine rotors pinot pins
Tkaný, Jan ; Mrňa, Libor (referee) ; Daněk, Ladislav (advisor)
The master´s diploma thesis elaborated as the master's degree M-STG Manufacturing Technology solves surfacing problems in the simulations of surfacing turbine rotors pinot pins. The work was seen as a preparatory work before the real surfacing. Topic commissioned by Siemens Industrial Turbomachinery Ltd. For welding plates test has been used the method of SAW and the base material was identical to turbine rotor material, X22CrMoV 12-1. Additional material was Fluxocord 42. Simulations were carried out in programs SYSWELD and Visual - WELD. The output of the simulation software are temperature and stress fields, material structures and creations of the CCT diagrams at the base material, filler material, and mixed area.
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