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Application of Technique of Oriented Foils in TEM
Buček, Petr ; Kruml, Tomáš (referee) ; Petrenec, Martin (advisor)
The master’s thesis is focused on the application of the technique of oriented foils in transmission electron microscopy. Dislocation structures were identified by this technique in both phases of polycrystalline austenitic-ferritic stainless steel SAF 2507 formed during low cycle fatigue at two plastic strain amplitudes ap. In individual grains the stress axis and the Schmid factors of active slip systems were determined. In austenitic grains, the planar structures were determined at both ap. In ferritic grains, the dislocation arrangement was different for the two observed ap. Individual screw dislocations and pile-up´s of edge dislocations were found at low ap = 1x10-4. Mixture of vein and wall dislocation structures were formed at high ap = 2x10-3. Observed dislocation structures were discussed in relation with the cyclic plastic response of the duplex stainless steel.
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Computational analysis of strength and fatigue of turbine blades
Polzer, Stanislav ; Suchánek, Miroslav (referee) ; Janíček, Přemysl (advisor)
This master thesis deals with steam turbine blade attachment. Main goal is to perform strength analysis of the given geometry under static and cyclic loads by FEM and software ANSYS. Every particular model is described separately with mentioning of the problems which had to be solved. To create model of material, the tensile tests has been performed and results has been evaluate. There were planned and performed the low cycle fatigue tests to create a model of ultimate states which is used to evaluate the fatigue life of the attachment. Results of the nonlinear FEM analysis is discussed and some improvements of the geometry has been proposed to achieve better state of stress. Finally, the plan of future work has been proposed.
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Determination of Shortcut Cyclic Stress-strain Curves of Superalloy Inconel 738LC at Elevated Temperatures
Šmíd, Miroslav ; Obrtlík, Karel (referee) ; Petrenec, Martin (advisor)
Multiple step tests under cyclic strain control have been performed using cylindrical specimens of cast polycrystalline Inconel 738LC superalloy at 23, 700, 500, 800 and 900 °C in laboratory atmosphere to obtain cyclic stress-strain curves. During cyclic straining of specimen were obtained cyclic hardening-softening curves. Their progress changed with temperature and strain amplitude. Evaluated cyclic stress-strain curves are shifted to lower stresses with increasing temperature. Surface relief was observed in fatigued specimens under SEM and metalography under optic microscopy. Slip markings were studied on specimen surface fatigued at 700 °C .Stress-strain response is compared and discussed in relation to the surface observations - persistent slip markings.
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Fatigue behaviour of nickel-based superalloy IN738LC with AlSi coating at 800°C
Hlavnička, Radek ; Juliš, Martin (referee) ; Hutařová, Simona (advisor)
This work deals with influence of applied protective AlSi layer on low cycle fatigue behaviour of substrate from nickel base superalloy Inconel 738 LC. Protective layer is made by thermal spraying, plasma spraying followed by heat treatment. The emphasis is especially concentrated to the microstructure evaluation of the protect layer and basic material, in addition, measurement of layer thickness and the microhardness in as sprayed conditions and after heat treatment. The fatigue behaviour is assessed by fracture area observation and fatigue cracks evaluation after low cycle fatigue tests carried out at 800 °C.
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Low cycle fatigue of EN-AW 7075 aluminium alloy
Bártková, Denisa ; Liškutín, Petr (referee) ; Věchet, Stanislav (advisor)
The main goal of this bachelor thesis is analysis of low-cycle fatigue of wrought alluminium alloy EN-AW 7075. In theoretical part of thesis, current facts about alluminium alloys and fatigue behaviour of material are summarized. Practical part contains evaluation of tension tests and analysis of experiments in low-cycle fatigue region. In additional, the microstructure of an alloy was observed.
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Low Cycle Fatigue of Magnesium Alloy AZ91
Julišová, Martina ; Podrábský, Tomáš (referee) ; Juliš, Martin (advisor)
The objective of the present study is to investigate the fatigue characteristics of cast magnesium alloy AZ91 after low–cycle fatigue tests at the indoor temperature. Squeeze casting specimens in both non–thermal treatment cast state and in solution annealing state were used as the experimental materials. Cyclic hardening/softening and fatigue life curves were obtained from the tests varying according to the way of thermal treatment. This bachelor thesis includes also fracture tests of specimens. Light microscopy and scanning electron microscopy were used for the investigation.
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Kinds of materials damage - II
Mašková, Lenka ; Nekvasil, Richard (referee) ; Neterda, Zdeněk (advisor)
Materials of production unit facilities are subjected to permanent damages while they are operating. Furthermore, there is a tendency to advance their working parameters that significantly increases risks of their damages. The goal of this thesis is to describe a process and mechanism of commonly occurred kinds of materials damage in the process industry. The thesis is focused on the material damage caused by the low-cycle fatigue and hydrogen embrittlement, and also the material disturbance evoked by the sudden fracture. Furthermore, the assessment technique of selected kinds of materials damage using theoretical formulae and their graphical representations using diagrams, schemes and figures for specific machineries are presented.
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