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Electron beam welding of ODS materials
Jankůj, Luděk ; Čížek, Jan (referee) ; Jan, Vít (advisor)
Thesis on Electron beam welding of ODS materials is divided into theoretical and experimental part. In the first part the theoretical research work focuses on the accurate description of the candidate materials in a research fusion reactor ITER. Following are detailed constructional ODS materials and tungsten alloy as a material of the first wall. The second part of the theoretical research deals with various possibilities of joining high-melting dissimilar materials such as brazing or electron beam welding as well, which will be established in the experimental section. The experimental part of the thesis deals with a joining ODS steel MA 956 with sintered carbide WC-Co and ODS tungsten. These materials are welded by electron beam. Individual samples are distinguished used filler material, preheating or welding parameters. This thesis contains photographic documentations of microstructure the welding samples, results from scanning electron microscopy, and measurements of microhardness across the weld metal.
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Electron beam welding of Ti 6Al 4V
Skalka, Jan ; Dupák, Libor (referee) ; Mrňa, Libor (advisor)
The thesis is dedicated to welding combination of titanium alloy Ti-6Al-4V and austenitic steels 1.4301 by electron beam. Based on literature studies of bonding titanium and its alloys with steels, it was proposed to select for welding interlayer of copper, which could limit the impact of intermetallic phases on the mechanical properties of the weld seam and enable the creation of weld. For welding the pipe samples were used three methods of welding with various welding parameters. Samples which remain after thermal cycling vacuum-tight, were then further analyzed (micro-hardness, tensile test, etc.).
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Surface treatment of selected steels using electron beam
Oríšek, Petr ; Jan, Vít (referee) ; Kouřil, Miloslav (advisor)
The thesis aims for the surface treatment of materials using electron beam. It includes a literary research describing physical principle and properties of the electron beam. This research also presents possible influencing of the beam and describes the construction of the device that generates the beam. Various applications of the electron beam for the material treatment are presented in the second part of the paper. Within this thesis an experiment with the heat treatment of the steel surface by the electron beam has been realized. The experiment was aimed at creating a layer as deep as possible without melting the surface. The results and their evaluation are presented in the experimental part of the thesis. The attention is also paid to selected process parameters.
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Structure and properties of electron beam penetration produced in steel AMS 5659
Říčan, Daniel ; Foret, Rudolf (referee) ; Kouřil, Miloslav (advisor)
This master thesis deals with the electron beam welding of the AMS 5659 steel used in industry for special hydraulic cylinders (Fig. 1). A theoretical analysis of electron beam welding and analysis of the influence of selected welding parameters on penetration characteristics are in the first part of the thesis. The second part contains an evaluation of the implemented experimental penetrations on samples of the steel in the hardened condition H1025 and after solution heat. It was also done a properties assessment of the same samples that were been hardened again. The light microscopy (SM), the scanning electron microscopy (SEM) and the measurement method of hardness according to Vickers were used for evaluation and comparison of the steel properties in the region of penetration and the heat affected zones properties.
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Electron Beam Control and Diagnostics for Advanced Technologies
Zobač, Martin ; Kolařík, Vladimír (referee) ; Průša, Stanislav (referee) ; Lencová, Bohumila (advisor)
The thesis deals with problems of control and diagnostics of electron beam technological devices which use electron beam for localised intensive heating of a material. A brief description of the electron beam welder MEBW-60/2 is included; the author has participated on its development and implementation. Main topics are the analysis of deflection system properties and the measurement of current distribution of the beam (so-called beam profiles). Geometrical aberrations, hysteresis, stability and dynamics of a single-stage magnetic x-y deflection system are described. Suitable measurement procedures and correction methods are introduced. Methods of transverse and longitudinal beam profile acquisition is presented using successive sampling of the local current density of the beam by a modified Faraday cup. The data processing and evaluation of characteristic beam parameters are shown. The presented methods were verified by fourteen experiments using the electron beam welder. The methods have proven to be useful in practical evaluation of the device properties.
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Influence of electron beam on graphene field effect transistors
Mareček, David ; Čech,, Vladimír (referee) ; Čechal, Jan (advisor)
This diploma thesis deals with electrical conductivity of a graphene sample, preparation of a graphene field-effect transistor and his irradiation by electron beam. In the theoretical part of the thesis, we describe electronic properties of graphene, preparation of graphene by CVD and its transfer to Si substrate with SiO_2 layer. Experimental part of this thesis is focused on the preparation of a graphene field-effect transistor for use in UHV conditions. Futher describes electron beam scanning over the transistor and creation of current maps of tranzistor. In the last part, the thesis deals with influence of electron beam on transport properties of graphene layer and doping of graphene layer by electron beam.
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Electron Beam Micromachining of Nonmetalic Materials
Dupák, Libor ; Mrňa, Libor (referee) ; Bábor, Petr (referee) ; Lencová, Bohumila (advisor)
The thesis deals with electron beam micromachining of nonmetallic materials like glass, ceramics and plastics. A brief description of the device on which the experiments were carried out is included; the author has participated on its development. Main topic is experimental study of influence of main electron beam parameters on results of machining. Examined parameters include accelerating voltage, beam current, focusing and speed of machining. Influence of beam deflection is analyzed. Method of sequential machining by repeated passes of the electron beam is presented. Main examined materials are quartz glass, alumina and selected plastics. The usefulness of the technology is shown by several practical applications.
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Design of focusing and deflection system of electron welder
Franc, Viktor ; Sháněl, Ondřej (referee) ; Zlámal, Jakub (advisor)
Main parts of the electron beam welder are the source of electrons, accelerator, magnetic lens with deflection coils and stigmator, welding chamber with manipulation stage for welding object and vacuum system. This master thesis starts the design of the electron beam welder prototype. More precisely it is aimed not only on electron optic design, but also on construction of magnetic lens, deflection coils, stigmator, welding chamber and vacuum system.
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Detection and measurement of electron beam in TEM images
Polcer, Simon ; Vičar, Tomáš (referee) ; Chmelík, Jiří (advisor)
This diploma thesis deals with automatic detection and measurement of the electron beam in the images from a transmission electron microscope (TEM). The introduction provides a description of the construction and the main parts of the electron microscope. In the theoretical part, there are summarized modes of illumination from the fluorescent screen. Machine learning, specifically convolution neural network U-Net is used for automatic detection of the electron beam in the image. The measurement of the beam is based on ellipse approximation, which defines the size and dimension of the beam. Neural network learning requires an extensive database of images. For this purpose, the own augmentation approach is proposed, which applies a specific combination of geometric transformations for each mode of illumination. In the conclusion of this thesis, the results are evaluated and summarized. This proposed algorithm achieves 0.815 of the DICE coefficient, which describes an overlap between two sets. The thesis was designed in Python programming language.
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