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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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The Material Selection for Bicycle Frames
Šály, Peter ; Petrenec, Martin (referee) ; Němec, Karel (advisor)
Bachelor's thesis summarises basic information about materials that are used for production of bicykle's frames. It concerns not only with common materials that are the most used nowadays, thus aluminium alloys and composite materials – carbon in the concrete, but it also pointed on the other, alternative materials. It also explains specific terms that relate to concrete materials or to their technological treating. Each material has listed characteristic which is objective thus measurable and it results from physical-chemical's properties and treating possibilities of concrete materials. It conveys assumption of frame behaviour made from this material. Subjective characteristic is also listed and it results from practice – from the feelings by real ride. Comparison of these two approaches resulted in conclusion which may help in choosing material for bicykle's frame which we have specific requirements on. Next thesis concerns with usage of concrete materials by various producers whether world producers or national ones, with orientation on brands which are interesting because of their treating of unusual materials or they are interesting because of their specific treating of common materials. There is a brief review of most used materials for concrete types of bicycle's frames at the end of the thesis.
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Effect cyclic heat treatment on structure of TiAl alloy
Vraspírová, Eva ; Němec, Karel (referee) ; Petrenec, Martin (advisor)
The subject of this master thesis is focused to the refining of the cast structure of gamma-TiAl–2Nb alloy using cyclic heat treatment and to the analysis of the grain refining mechanism. Structure evolution after applied cycles of heat treatment was characterized using light, laser and electron microscopy and using microhardness tests. Application of five heat treatment cycles during which two phase transformations (eutectoid and alpha-recrystallization reactions) repeatedly took place resulted in refining of the cast columnar structure having the mean grain size 512 microns to fully lamellar structure containing gamma and alpha2 phases having the mean grain size 229 microns. Lamellae thickness of gamma was not changed while the thickness of alpha2 phase decreased, up to 78 nm. Refining of alpha2 phase resulted in the increase of the microhardness by 20 %. The recrystallized cast structure obtained by cyclic heat treatment and the knowledge on the mechanisms of the refining the structure were compared with the literature data and were discussed in order to propose more efficient procedure for refining thermal treatment of cast TiAl alloys.
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On the effect of lacquer-setting technology on the quality of a joint
Smékal, Jan ; Petrenec, Martin (referee) ; Píška, Miroslav (advisor)
The thesis is divided into two parts. At first it deals with the process of powder coating technology, gluing technology and rubber. Then the thesis continues with the experimental part, which includes process of making glued joints and evaluation of tensile test of those glued joints. The effect of lacquer-setting technology on quality of a joint cannot be reliably evaluated based on results achieved from tensile test. Analysis of results was made as well as suggestion for improvements of experiment for future thesis.
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Technological and economic analysis of the production for the automotive industry
Sedláková, Eva ; Petrenec, Martin (referee) ; Píška, Miroslav (advisor)
The thesis deals with an analysis of an existing technology of thread forming under various technological parameters used in car industry. Furthermore, it characterizes metric threads, their production and quality control, forming taps, process fluids and other process parameters. In the experimental part the experimental tests with a conventional and CNC drilling machines were carried out. The influence of various process fluids on surface and thread quality have been assessed statistically. The technical-economic evaluation of the process fluids and their effect on the technology has been made. The work supports a beneficial role of soap and polymers as convenient tribological means at thread forming.
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Recrystallization study of free-cutting steel by in-situ SEM/EBSD technique
Babinský, Tomáš ; Němec, Karel (referee) ; Petrenec, Martin (advisor)
Placing recrystallization annealing in a manufacturing proces is often necessary in order to restore plasticity of worked blanks right before working products to its final shape. For better understanding of processes which are taking place in a material during annealing the use of in-situ techniques is favorable. Such observations enable us to watch changes in the materiál in real time at the original spot. Observations at grain-level are ideally made with scanning electron microscope – SEM by electron back-scattered diffraction – EBSD. The technique makes watching nucleation, growth and potential coarsening of recrystallized grains possible. Special construction of a tensile stage allows us to watch changes of a sample during tensile tests which can be used in observing influence of MnS inclusions on plasticity of free-cutting steels. Materials studied in this work are commonly used free-cutting steel 11SMnPb30 and its lead-free alternative 11SMnBi30.
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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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On the effect of lacquer-setting technology on the quality of a joint
Smékal, Jan ; Petrenec, Martin (referee) ; Píška, Miroslav (advisor)
The thesis is divided into two parts. At first it deals with the process of powder coating technology, gluing technology and rubber. Then the thesis continues with the experimental part, which includes process of making glued joints and evaluation of tensile test of those glued joints. The effect of lacquer-setting technology on quality of a joint cannot be reliably evaluated based on results achieved from tensile test. Analysis of results was made as well as suggestion for improvements of experiment for future thesis.
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