JOINIG OF MG ALLOY AZ31B BY SELECTED TECHNOLOGIES

This contribution presents metallurgical joining of Mg alloy AZ 31B by several technologies - Friction Stir Welding - FSW, Laser Beam Welding - LBW, soldering and their mutual comparison. The difficulty of joining Mg alloys is connected with the strong MgO layer, low ductility of the weld metal (WM), a presence of intermetallic phases connected with the hardness increase. To successfully join Mg alloys, a precise setting of welding parameters is needed. The welds are susceptible to low mechanical properties as all samples fractured at WM. From the tested methods, laser beam welding proved the best results, because laser welding is the fastest and weld strength reached the highest values, i.e. 87% of BM (base metal) strength

WELDING OF NITINOL BY SELECTED TECHNOLOGIES

Nitinol is a perspective alloy that is difficult to weld because of its high sensitivity to heat, atmospheric gases and the NiTi phase instability. We evaluated several welding techniques with regard to their applicability to weld fine pseudoelastic NiTi wires. Namely, we tested the microplasma arc, laser, electron beam, resistance and capacitor discharge welding. In conclusion, the behaviour of the weld for any of the implemented welding techniques is similar; it leads to a loss of mechanical properties in the welded joint caused by a recrystallization and an increased amount of brittle intermetallic phases. Yet, under perfect shielding and with a minimum heat input, the welds could, as a whole, retain the majority of their properties, and, as such, have the desired properties close to the base metal

Lokal watchdog.

This master's thesis focuses on studying the function of civil control over local government and maps this practice both in the Czech and the Slovak Republic. It pursues the following questions: what is the role of watchdog NGOs in civil society and democracy? What is the watchdog concept? What is corruption and how to fight against it? Through practical examples and several case studies it describes the basic interactions of watchdog with the local environment, the sources of civil control legitimacy, and the obstacles and limits to watchdog work

web aplication eShop - clothes

Tato práce se zabývá návrhem a implementací internetového obchodu zaměřeného na prodej oblečení s možností vkládání vlastních motivů. Cílem této práce je mimo vytvoření internetového obchodu, optimalizace pro vyhledavače pomocí metodologie SEO. Teoretická část se zabývá studií SEO, v praktické části je uveden detailní popis celé aplikace a následná praxe z hlediska SEO.This thesis deals with design and implementation of internet shop specialized in sales of clothing, with the possibility of inserting their own motives. The aim of this thesis is outside the creation of an Internet Shop, search engine optimization through SEO methodology. The theoretical part deals with the studies of SEO, in the practical part is given a detailed description of the entire application and follow-up practice in terms of SEO.Katedra informačních technologiíDokončená práce s úspěšnou obhajobo

HSS DEPOSITION BY PTA – FEASIBILITY AND PROPERTIES

High speed steels (HSS) as iron alloys reinforced by carbides of tungsten, chromium, vanadium and/or cobalt are known for more than 100 years. HSS is commonly used for cutting tools fabrication because of their high hardness, ductility, and strength and temperature resistance. Recently many different kinds of thin layers are often deposited on HSS tools in order to increase their lifetime. HSS are produced by conventional metallurgical methods and the tools are hardened by quenching and tempering. Recently, large part of HSS tools are produced by powder metallurgy (i.e. HIP-hot isostatic pressing). There are also some studies about thermal spraying of HSS but there is no evidence about Plasma Transfer Arc cladding of HSS. Two powders of HSS 23, resp. HSS30 grade were selected and deposited by Plasma Transfer Arc (PTA) and pulsed PTA on to mild steel substrate. In order to find the ability of thick layer forming, four layers cladding were used. To minimize heat input the influence of 76 Hz pulsation was also studied. Vickers hardness was measured on cross section and metallography of coatings was done. It was found that with selected parameters thick layer of HSS can be deposited. Pulsation increases the hardness of coatings in comparison with layers produced by direct current PTA. PTA and pulsed PTA methods of HSS parts fabrication can be used for both manufacturing and reparation of cutting tools and also for 3D additive manufacturing process