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Optimalization of parts bonded by hot crimping
Liškář, Ladislav ; Řiháček, Jan (referee) ; Lidmila, Zdeněk (advisor)
The thesis describes the procedure for verifying the conceptual ideas of the company. Design and production of prototypes, testing and evaluation, quantifying savings. Two variants of crimped bond were chosen. For each was length of shaft changed to three and four crimped grooves. These prototypes were tested in two static and one dynamic tests. Recommendation for company is continue with other phases of development for shaft with four grooves.
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Structural and Mechanical Characteristics of Nickel-Alloyed Ductile Cast Iron
Tesařová, Hana ; Kohout, Jan (referee) ; Kruml, Tomáš (referee) ; Konečná,, Radka (referee) ; Pacal, Bohumil (advisor)
The aim of this dissertation work is the evaluation of the influence of nickel alloying on the structure and mechanical properties, both monotonic and dynamic, of nodular cast iron with ferritic and bainitic matrix. Two chock melts with 0.5 and 2.7 % Ni were used to study the nickel influence. The quantitative evaluation of structure of these melts using image analysis was done and basic tensile mechanical properties were determined. Subsequently, the time optimization of two-stage ferritic annealing and isothermal austempered heat treatment at 375 °C was performed with the aim to obtain optimal ferritic and bainitic structures with best static and dynamic mechanical properties. After ferritic annealing the nickel alloying contributes to substitution hardening of ferritic matrix which positively affects its strength and other mechanical properties. The higher nickel content in the bainitic structure causes the shift of phase transformation times to longer times which results in restricted production of small carbides and in bigger volume of retained austenite. These features were confirmed by observation in transmission electron microscope. Precise tensile and low cycle fatigue tests at temperatures 23 and – 45 °C were performed on the optimized structures of both nodular cast irons. As a result of the notch effect of graphite nodules, microplastic deformation of both nodular cast irons was observed at stresses which were lower than the yield stress. The Hollomon's equation very well describes the individual parts of tensile curves for both nodular cast irons including their mutual comparison. From the low cycle fatigue tests, the cyclic hardening/softening curves, the evolution of elastic modulus and hysteresis loop shape parameters, cyclic stress-strain curves and fatigue life curves were obtained for both temperatures and materials. Moreover, the decrease of retained austenite volume was measured by neutron diffraction and the evolution of surface relief was characterized during cyclic straining for both austempered nodular cast irons at both temperatures. On the basis of these results both cyclic plasticity and fatigue degradation mechanisms in relation to the cyclic strain localization were described for both nodular cast irons.
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Determination of mechanical properties of light metals and alloys and composites via small punch test
Langer, Jiří ; Dobeš, Ferdinand (referee) ; Válka, Libor (advisor)
The aim of diploma thesis is estimate mechanical properties (yield strength, maximum strength and elongation) of light alloys by means of SPT. For the experiments were selected aluminium alloys (Al 2024, Al 6082 T6, Al 7020 and NASA 398) magnesium alloys (MgZnMn, AZ31, AZ61) and composites (AZ91 + 20 % saffilu a Al + Al4C3). Theoretical part of this thesis is focused on analysis of conversion formulas, which were made from SPT data and conventional testing. Experimental part is dedicated to evaluation of experimental data and critical analysis validity of conversion formulas. In this part of thesis is discused the problematics of reproducibility methodology of SPT.
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Assessment of heterogeneous properties butt welds in laser welding and electron beam welding
Rozsypal, Oldřich ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
The project was developed within the engineering degree in engineering technology, and is focused in welding together of two different materials. Welds will be done on a high strength steel Domex 420 MC and deep drawing steel DC01 using laser welding, and will be compared with the method of electron beam welding. Part of this project is a scientific research describing the basic physical principles of both methods, different types of lasers, welding material properties and inspection of welds. In the experimental part was carried tensile test, macroscopic and microscopic examination. Finally, work is to evaluate the individual tests.
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Optimalization of parts bonded by hot crimping
Liškář, Ladislav ; Řiháček, Jan (referee) ; Lidmila, Zdeněk (advisor)
The thesis describes the procedure for verifying the conceptual ideas of the company. Design and production of prototypes, testing and evaluation, quantifying savings. Two variants of crimped bond were chosen. For each was length of shaft changed to three and four crimped grooves. These prototypes were tested in two static and one dynamic tests. Recommendation for company is continue with other phases of development for shaft with four grooves.
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Mechanical Properties of Plastics
Suchý, Marek ; Němec, Karel (referee) ; Molliková, Eva (advisor)
This bachelor thesis deals with the plastics in terms of their internal structures. Analyzes the impact of these characteristics on the resulting mechanical properties of materials. Furthermore, examining the external influences significantly on the polymer chain operates. Concludes two basic methods for the detection of mechanical properties - tensile test and 3-point bend tests.
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Influence of Homogenizing on Mechanical Properties of AZ91 Alloy
Provazníková, Andrea ; Liškutín, Petr (referee) ; Věchet, Stanislav (advisor)
This bachelor thesis includes photos and graphic representations of the influence of heat treatment on the mechanical properties of magnesium alloy AZ91. The structures of the alloy are recorded on the light microscopy pictures as well as photographs taken using a scanning microscope of fracture areas in the material. Results of a Tensile Test determining the strength and plastic properties and measuring of hardness and microhardness of the material are also included.
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Změna vlastností nerezových ocelí v agresivním prostředí
Dobrovolný, Pavel
The bachelor thesis on the topic: Changing the properties of stainless steels in aggressive environments examines the influence of heat exposure and aggressive environment on mechanical properties of stainless steels. The theoretical part describes the principle of corrosion, possibility of spreading corrosion, selected corrosive environments, types of corrosion and the factors that affect the intergranular corrosion of stainless steels. The practical part deals with verification experiment that consists in finding the influence of corrosion degradation on mechanical properties of stainless steels. Etalons and corrosion exposed samples from various grades of stainless steels were subjected to tensile test. The evaluation experiment was done by comparing the measured values of tensile test. Practical measurements complement metallographic images.
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