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Proceedings of the 16th International colloquium Mechanical Fatigue of Materials
Polák, Jaroslav ; Kruml, Tomáš ; Man, Jiří
The XVI International Colloquium on Mechanical Fatigue of Metals was organized by the Institute of Physics of Materials, Academy of Sciences of the Czech Republic in Brno, in September 24-26, 2012. The Colloquium has been opened to participants from all countries interested in the subject of fatigue of metallic materials. The proceedings contains 39 abstracts of 35 oral and of 4 poster contributions by 122 authors from 18 countries to be presented during the Colloquium.
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Propagation of inclined cracks to the interface of ceramic laminates
Novotná, Lenka ; Trunec, Martin (referee) ; Chlup, Zdeněk (advisor)
Composite materials with laminated structure provide advantages which are utilised during component design. Low density, temperature and chemical stability are the profitable properties predetermining application of ceramic laminates. The main obstacle for wide spread of ceramic materials is their inherent brittleness. Therefore, in this thesis, the crack propagation in ceramics laminates has been extensively studied. Laminated structures with various volume fractions of components (alumina and zirconia) were prepared by electrophoretic deposition. Evaluation of crack propagation through the interface and determination of basic mechanical properties was conducted on the basis of extensive literature search. Crack deflection originated in both presence of internal stresses and differences in elastic modulus during the crack interface passing was monitored. A special type of specimen geometry was employed with the aim to set arbitrary angle between crack and interface. It was experimentally found that the degree of crack deflection is dependent on entering angle and volume fraction of components. Higher crack deflection was already found in the bulk of the test piece comparing to the test piece surface. The 3D fracture surface reconstruction generated using laser confocal microscopy was used in this detailed crack propagation study. Further basic elastic and strength characteristics of laminates were determined and compared to those obtained from monolithic materials. The validity of the mix rule for elastic characteristics was confirmed by comparing of elastics modulus. The most reliable method for elastic modulus determination was marked the dynamic resonance method due to low scatter and consistency in measurement. The flexural strength of all laminates tends to be close to the flexural strength of the weakest component. Therefore the mix rule is not applicable for flexural strength estimation on the contrary of elastic characteristics. The change of component volume fraction leads only to change of flexural strength scatter. Thanks to gained knowledge about crack propagation and basic characteristic determination will be possible to design ceramic laminates more efficiently for given needs of application.
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Milling of internal threads in Bosch injection unit bodies
Krčál, Petr ; Prokop, Jaroslav (referee) ; Humár, Anton (advisor)
At the beginning of this diploma thesis I describe the production of different types of threads (with special emphasis on the production of internal threads), then I discuss different types of application of abrasion resistant coating by PVD and CVD, I describe their main advantages and disadvantages. Further, this diploma thesis explains particular mechanisms and forms of tool wear on tool with coating. In the second part of this diploma thesis the analysis of the current status of the production of internal threads in the Rail (high-pressure chamber) is made. In the last part I compare six different threads cutters by the use of a scanning electron microscope
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Multimedia communication
Vondra, Zdeněk ; Horný, Stanislav (advisor) ; Skrbek, Jan (referee) ; Jurášková, Olga (referee)
Multimedia is a form of communication and sharing knowledge using synergic effect of parallel connected communication channels. Its main use is in producing communications products and services and in design of user interfaces. Main objective of this dissertation is to develop and create a model of multimedia communication for better understanding of the meaning and the purpose of using multimedia forms in communication process. The model will describe a system of elements and parameters of multimedia communication within the internal and external context. Another objective of this dissertation is to develop multimedia communication methodology that will be used for the design, development and evaluations of concepts of multimedia communication. The methodology will be created by applying the model of multimedia communication into the procedure structure. In theoretical way this dissertation is based on analysis of different definitions and approaches to the multimedia communications topic. This is followed by an analysis of communication theories, concepts of media, multimedia, delivery channels, and communication functions. The theoretical part is followed by the outcomes of the research in practice of four different fields of multimedia use. The knowledge gained is analyzed in the following parts in purpose of creating the model of multimedia communication and the methodology which is derived from the model. The methodology is further validated through case studies and the recommendations for further development are formulated. The model and the methodology of multimedia communication created in this dissertation present complex view on multimedia communication topic that is considered as a useful tool for meeting a specific communication purpose. Dissertation provides mechanics for use and study of multimedia communication and also defines the opportunities for further development of the methodology.
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název v anglickém jazyce není uveden
Kolesová, Hana ; Grim, Miloš (advisor) ; Slípka, Jaroslav (referee) ; Nečas, Emanuel (referee)
Branchial arches region and its blood vessels are extensively transformed in the embryonic development. Aim of this study is to investigate mechanisms of the branchial arches region development and to study how a morphogen Sonic hed gehog (Shh) participate on the formation and remodeling of branchial arches and their blood vessels. Influence of Shh was evaluated based on the changes caused by its inhibition in vivo. Shh function was inhibited with an anti-Shh antibody, which was produced into the embryo from the applied hybridoma cells. Shh signaling cascade was also inhibited by cyclopamine. Results show that Shh is important for dc novo format,ion of the blood vessels in the branchial arches region. Further Shh is necessary for stabilization of the vessel wall, mainly for anterior cardinal vein. Shh also alfects later vessel development and transformation, which includes i.e. fusion of the dorsal aorta, branching of the internal carotid artery and outflow tract development. Short time inhibition of Shh has minor effect on the apoptosis and proliferation activity of the branchial arches region mesenchymal cells. We assume that Shh signals directly to the blood vessels endothelial cells, as Shh receptor ptel is also expressed in endothelial cells and its signal is reduced with Shh inhibition. In studied...
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CNC Programming if the Single Point Incremental Forming
Ladecký, Tomáš ; Slaný, Martin (referee) ; Píška, Miroslav (advisor)
V současné době se zvyšuje potřeba rozvoje agilních výrobních postupů, které lze snadno přizpůsobit neustálému zavádění nových produktů na trh. Jednobodové inkrementální tváření je nový, inovativní a proveditelný tvářecí proces s jednoduchým uspořádáním. Proces se provádí při pokojové teplotě (tváření za studena) a vyžaduje CNC stroj, nástroj s kulovou hlavou a jednoduché příslušenství pro uchycení obrobku plechu. V samotném procesu jde o přírůstkové formování, řízené CNC programem. Plastická deformace je lokalizována pod formovacím nástrojem takže plech je tvářen souhrnem pohybů lokální plastické zóny. Tento proces je zdlouhavý a proto se hodí pouze pro prototypovou výrobu nebo pro malé výrobní dávky. Na druhé straně umožňuje vyšší tvářitelnost ve srovnání s konvenčními procesy tváření, umožňuje použití levných nástrojů a také je charakterizován krátkou dobou od návrhu po výrobu produktu. Tato práce je výsledkem mezinárodní spolupráce Danmarks Tekniske Universitet v Lyngby a Instituto Superior Técnico v Lisabonu. Práce začíná krátkým hodnocením dílčích tvářecích procesů, pokračuje představováním jednobodového inkrementálního tváření a identifikací jeho praktických aplikací. Teoretická část obsahuje přehled nového rámce pro jednobodové inkrementální tváření, který je vytvořen na základě analýzy styku třecích sil. Praktická část projektu poskytuje úplný popis experimentálních technik použitých pro charakterizaci materiálů a stanovení limitů tvářitelnosti, dále se analyzuje vliv různých vstupních parametrů procesu (poloměru nástroje, tepelné zpracování materiálu obrobku, druh maziva,...). Tato část také obsahuje přehled experimentálního uspořádaní procesu jednobodového inkrementálního tváření i krátký popis CAD / CAM vývoje tří testovacích modelů. Poté jsou popsány v samostatné kapitole výsledky pozorování a analýzy hlavních parametrů procesů, které ovlivňují tvařitelnostní limity v jednobodovém inkrementálním tváření v souvislosti s aplikovaným teoretickým rámcem. Výsledky experimentů z časti objasňují probíhající mezinárodní diskusi kolem tvářitelnosti mechanismu jednobodového inkrementálního tváření vzhledem k tradičním metodám tváření. Jako logické pokračování prováděných experimentů, byla práce rozšířena na více-stupňové jednobodové inkrementální tváření, které umožňuje tváření součástek (kalíšku) se svislými stěnami ve více krocích. Za účelem objasnění procesů spojených s tímhle procesem byly navrženy a ve čtyřech krocích vyrobeny dva experimentální modely. Hlavním přínosem této práce k více-stupňovému jednobodovému inkrementálnímu tváření byla úspěšná výroba součásti s nekruhovým průřezem a kolmými stěnami. S cílem aplikovat celkové znalosti získáných v předchozích částí práce byla vyrobena prototypová součást. Popis designu a vývoje prototypu je součástí práce. V neposlední řadě jsou celkové závěry uvedené v poslední kapitole. Předpokládá se, že tato práce přizpívá k lepšímu pochopení mechanismu jednobodového inkrementálního tváření.
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INFLUENCE OF LASER CUTTING AND PUNCHING ON MAGNETIC PROPERTIES\nOF ELECTRICAL STEEL M470-50A
Bulín, Tomáš ; Švábenská, Eva ; Hapla, Miroslav ; Ondrůšek, Č. ; Schneeweiss, Oldřich
Electrical steel M470-50A belongs to the most often used materials in electrical machines. Due to this fact, it is desirable to know the magnetic parameters after processing raw sheets into the required shape. Basic parameters of mechanical, electrical, and magnetic properties of the sheets are usually obtained from the producer but the magnetic properties are changing in dependence on additional machining processes. The aim of this study is to describe changes in parameters of magnetic behavior after punching, laser and spark cutting of the original sheets. The basic information of structure was obtained by optical and scanning electron microscopy. The magnetic parameters were acquired from the measuring of magnetic hysteresis loops in dependence on saturation fields and frequencies. The results are discussed from the point of view of applied\ncutting technology with the aim to obtain the best magnetic parameters and consequently a higher efficiency of the final product. Results can be used as input parameters in simulation of the electrical machine.
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STRAIN ENGINEERING OF THE ELECTRONIC STRUCTURE OF 2D MATERIALS
del Corro, Elena ; Peňa-Alvarez, M. ; Morales-García, A. ; Bouša, Milan ; Řáhová, Jaroslava ; Kavan, Ladislav ; Kalbáč, Martin ; Frank, Otakar
The research on graphene has attracted much attention since its first successful preparation in 2004. It possesses many unique properties, such as an extreme stiffness and strength, high electron mobility, ballistic transport even at room temperature, superior thermal conductivity and many others. The affection for graphene was followed swiftly by a keen interest in other two dimensional materials like transition metal dichalcogenides. As has been predicted and in part proven experimentally, the electronic properties of these materials can be modified by various means. The most common ones include covalent or non-covalent chemistry, electrochemical, gate or atomic doping, or quantum confinement. None of these methods has proven universal enough in terms of the devices' characteristics or scalability. However, another approach is known mechanical strain/stress, but experiments in that direction are scarce, in spite of their high promises.\nThe primary challenge consists in the understanding of the mechanical properties of 2D materials and in the ability to quantify the lattice deformation. Several techniques can be then used to apply strain to the specimens and thus to induce changes in their electronic structure. We will review their basic concepts and some of the examples so far documented experimentally and/or theoretically.
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