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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
151

Dynamické materiálové modely ve tváření kovů a slitin / Dynamic models of material in metal forming

Kudláčová, Barbora January 2017 (has links)
The aim of the Diploma Thesis is to discuss the creation of material models for the forming technology in quasi-static and dynamic loading conditions and to practically propose a methodology of modeling the mechanical behavior of the selected material for dynamic load conditions using the Split Hopkinson Tensile Bar Test. The presented work contains an overview and analysis of individual experimental methods with the influence of the strain rate in terms of the extent of their suitability, the analysis of the plastic deformation mechanism, an overview of the mathematical mechanical behavior models for the materials used for technological practice and the evaluation of the mechanical behavior of stainless steel according to ČSN 41 7348 in terms of flat formability incl. evaluation of microstructure, fractographic analysis and evaluation of results from ferromagnetism measurement of steel after dynamic loading.
152

Termomechanická interakce vnějších ledových slupek a podpovrchových oceánů na ledových měsících Jupiteru a Saturnu / Thermomechanical interaction between outer ice shells and deep oceans on icy moons of Jupiter and Saturn

Malík, Jiří January 2018 (has links)
The thesis contains a survey of numerical tools for studying thermomechanical interactions of a two-phase system contained in a domain with an upper bound- ary that forms a free surface. The enthalpy diffused-interface formulation is used for an approximation of the phase change interface and the computing algorithm is benchmarked against an analytical solution of the Stefan problem. Arbitrary Lagrangian-Eulerian kinematical description of the continuum is applied to over- come the difficulty in the form of the free surface. The validity of the approach is examined on a thermal convection benchmark problem. 1
153

Studium vlivu organických vláken na požární odolnost betonu / Study of the influence organic fibres on the fire resistance of concrete

Klobása, Jan January 2022 (has links)
The master thesis is focused on current issues of concrete behaviour under high temperatures. In the theoretical part, a search of knowledge about changes in concrete, which take place when exposed to thermal loads, which simulates the effect of fire, is performed, and summarized. It is also important to summarize the changes in the individual components that are used to produce concrete. This work describes the effect of high temperatures on mechanical and physical properties as well. There is an information about the most used fibres and their function in concrete. Emphasis is placed on describing the possibility of using recycled PET or cellulose fibres due to the positive environmental impact. In the experimental part, recipes with different types and amounts of fibres are proposed. The subject of the research was to determine how individual types and amounts of fibres affect the physical mechanical properties of concrete and their suitability for use at high temperatures. Microscopic scanning and study of changes in the structure of concrete was also performed.
154

Využití dat pro systém hospodaření s vozovkou na silnicích II. a III. tříd k posouzení účinků vnějších vlivů na povrch vozovek / Usage of data for the pavement management system on roads II. and III. classes to assess the effects of external influences on the road surface

Skořepová, Eliška January 2022 (has links)
The master thesis is focused on sorting collected primary data, their subsequent analysis and further comparison in the field of road defects. The collection of pavement failures was done by visual inspection with its recording to a computer for the pavement management system. The data later underwent detailed analysis with the aim to find a potential link between the road defect and the location of the damaged section. The study took place on 2nd and 3rd class roads in the Liberec Region, with special focus on those located near forests. The data collection itself took place in the Liberec Region in 2021. The processing and subsequent evaluation of collected data was done thanks to the availability of comparable data sets from 2014 and 2019 to 2021, so the development of road defects of the selected road network in relation to the surrounding afforestation could be assessed. The last part of this master thesis compares results in different classification levels, time periods and levels of afforestation.
155

Funkční zkoušení recyklátů do pozemních komunikací / Performance tests of the recycled aggregates to roads

Karásková, Romana January 2012 (has links)
The work is divided into two parts. The practical part deals with the testing properties of soils which are using in new road in Nové Město na Moravě and the testing of recycled materials which could replace this soils from road. The aim this part is to obtain values of elastic modulus which are then inserted into the computational model. In the second part of work the track road is modeled in the software which uses the Finite Element Method to calculate and respect physical properties of different materials and a load. The result of work will be studies with comparison of displacement and stress generated to using existing soils and recycled materials.
156

Posouzení asfaltového koberce drenážního a tenkého s asfaltem modifikovaným přísadou TecRoad / Evaluation of porous ashalt and acphalt conrete for very thin layers with asphalt modified by TecRoad additive

Kaška, Zdeněk January 2012 (has links)
This work is focused on the design and determination of the properties of porous asphalt and asphalt concrete for very thin layers with TecRoad addition. The water sensitivity, particle loss, stiffness, fatigue and low temperature characteristics and resistance to permanent deformation are determined for a description of mixtures properties. Subsequently, the mixtures are compared and recommendations for use in maintenance and reconstruction of roads are prepared.
157

Aplikace metody difrakce zpětně odražených elektronů v materiálovém inženýrství / Application of Electron Backscatter Diffraction in Materials Engineering

Man, Ondřej January 2010 (has links)
The thesis deals with principles and common applications of the electron backscatter diffraction (EBSD) method. Some practical experience in application of the method to a study of highly deformed structure of copper and its thermal stability is described on one hand, and, on the other hand, to a study of phase composition of TRIP steel on various levels of imposed strain. The limitations of EBSD method are discussed along with its resolution in comparison with other complimentary techniques.
158

Vliv morfologie povlaku Zn na mezní podmínky při tažení tenkých plechů / Influence of Zinc Coating Morphology on Limit Conditions Formability of Thin Sheet Metal

Císařová, Michaela January 2012 (has links)
The doctor thesis deals about the influence of zinc coating morphology on limit conditions formability of a thin sheet metal. In the introduction of the thesis is discusesed about current problems searching the most suitable morphology of the steel sheet metals, a method of appliing to the zinc sheet metal. The hot dip zinc coating is discussed in next chapter, the topical knowledges about the influence of the individual factors have some effect to coat calibre and quality. In literary researchs are discussed the concrete technological tests of zinc coating to harder sheet metal forming, the theory of the bend and the basic theory of pressing sheet metal. In following chapter is devoted interpretation selected technological tests, according to that is described behaviour, characteristics, influence of zinc coating formability of basic material and his morphology.
159

Studium vlivu rychlostních a teplotních parametrů na tvařitelnost Ti slitin / Study of Influence of Strain Rate and Temperature on Formability of Titanium Alloys

Šlais, Miroslav January 2012 (has links)
The PhD thesis deals with the influence of temperature and strain rate on the mechanical behaviour of the Ti-6Al-4V titanium alloy. After verification tests under static loading conditions, the samples were deformed at high strain rates and elevated temperatures, using device for Hopkinson pressure bar test. The result is dependence of stress and strain rate on strain in the temperature range of 20 to 500°C. The deformed shape of specimen from the Taylor anvil test is compared with the results of the simulation in the Ansys – LS Dyna software. The parameters of Johnson-Cook equation were determined from these experiments. Also, the influence of loading conditions on the microstructure was studied. Both optical and scanning electron microscopes were used for the observations. During the research, some adjustments to the experimental devices were made in order to suppress the high-frequency components and noise in the recorded pulses. A functional tensile test adapter for the Hopkinson test was developed; it is registered under No. 2007/008 at the Technology Transfer Office of BUT.
160

Effects of Non-Newtonian Lubricants on Surface Roughness in Point Contacts / Effects of Non-Newtonian Lubricants on Surface Roughness in Point Contacts

Ficza, Ildikó January 2015 (has links)
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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