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Extremely low cycle fatigue life of non-ferrous alloys
Judas, Jakub ; Kohout, Jan (referee) ; Zapletal, Josef (advisor)
This thesis is focused on fatigue behaviour of aluminium alloy 2024-T351 in low cycle and extremely low cycle fatigue regime. Test specimens were firstly subjected to quasi-static tensile and compression tests to establish basic mechanical properties of the experimental material. Fatigue tests were conducted in strain-control mode, when cyclic plastic response and S-N curves were determined. All of the experiments were conducted at room temperature. Shapes of mechanical hysteresis loops are dependent on the strain amplitude and clearly exhibit cyclic plasticity of the alloy. Cyclic deformation curve was fitted by power regression function and subsequently compared with the tensile test. Experimental data of the S-N curves were fitted by Manson-Coffin and Wöhler-Basquin law. The discrepancy of the fatigue data was observed in the extremely low cycle fatigue regime. Based on this phenomenon, new regression function was used to overcome shortening of fatigue life in the extremely low cycle regime.
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Analysis of an accuracy of laser scanning
Vacová, Dominika ; Kohout, Jan (referee) ; Volařík, Tomáš (advisor)
The main goal of this master thesis is processing a point cloud with respect of possibilities of a registration clouds based on reference objects or on objects in general. This thesis studies transformations to the reference coordinate system S –JTSK. The first part of this thesis describes a theoretical background of the laser scanning and its use. A practical part shows the results and the evaluation of whole research.
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Metallic materials used for dental prostheses
Kožiol, Martin ; Kohout, Jan (referee) ; Věchet, Stanislav (advisor)
The topic of the bachelor's thesis is the use of metallic prosthesis and implants in dental medicine. The main point is to elaborate the summary of metallic materials and their mutual comparision in the terms of properties and individual application. For the clearly understand, there has to be defined a biocompatibility which along with mechanical properties serves for categorizing materials capable of application in the form of dental prosthesis. At the end is discussed about future of metallic materials in dental medicine.
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Biocompatible titanium and cobalt alloys and their aplications
Volná, Kateřina ; Kohout, Jan (referee) ; Věchet, Stanislav (advisor)
This work is written in the form of literary research and deals with titanium and cobalt alloys and their application in dental medicine. Production of the individual metals, their mechanic, physical as well as chemical characteristics and various alloys which these elements can form are described in the first part. Furthermore, biocompatibility and basic division of biocompatible materials are explicated here. The work also deals with the basic requirements placed upon the materials used in dental medicine. Subsequently, five particular alloys are introduced: Ti-6Al-4V, Nitinol, Oralium, Oralium Ceramic and Ceramill Sintron and their characteristics and usage are described. In conclusion, the individual metals and their alloys are evaluated.
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Fatigue properties of structural steel 11 523
Kudelka, Martin ; Kohout, Jan (referee) ; Věchet, Stanislav (advisor)
This bachelor thesis studies the mechanical properties of steel 11 523 in the state after normalization annealing. Its purpose is an assessment of the structure in material and determination of static and fatigue characteristics. In the theoretical part of thesis, there is explained, how to divide and mark kinds of steel. There is also a mention about basic parameters of material and the main attention is paid to fatigue and its laws. The metallographic analysis, tensile test and the fatigue test were realized in the experimental part of thesis. Experimentally determined values were compared with data in the literature.
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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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Influence of Plasma-nitriding on Fatigue Life of High-strength Steels under Biaxial Loading
Major, Štěpán ; Kohout, Jan (referee) ; Růžička,, Milan (referee) ; Obrtlík, Karel (referee) ; Pokluda, Jaroslav (advisor)
This work deals with fatigue life and fractographycal analysis of plasma-nitrided and virgin specimen made of the low-alloy high-strength steel. Specimens were subjected to in-phase combined bending-torsion loading. The work is focused on three groups of problems. The first group of problems was associated with the fatigue life and its prediction. The objective was to examine a relationship between the presence of the nitrided layer and fatigue life. The application of surface layers has significantly improved the fatigue life in the high-cycle region. An extended comparison between classical and advanced multiaxial criteria was performed. Criterions proposed by Marin and Matake were found to be most precise. The second objective of this work was to examine a relationship between the loading ratio ( is the bending amplitude and is the torsion amplitude ) and the fracture surface topography in the highcycle fatigue. Properties of fracture surfaces were quantified by many roughness and fractal parameters. Many roughness parameters start to incrise rapidly above a critical value of the loading ratio zc = 0,5. The last part of this work deals with the fractographical analysis of fish-eye cracks that were formed in plasma-nitrided steel specimens under symetrical bending, symetrical torsion and biaxial in-phase bending-torsion combinations.
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Accuracy testing of mobile mapping system MOMAS
Nováčková, Soňa ; Kohout, Jan (referee) ; Hanzl, Vlastimil (advisor)
The aim of this thesis is to introduce the mobile mapping system MOMAS, which is owned by Geodis Brno, spol. s.r.o. and test the accuracy of the system. Perform data collection and processing of data in the workplace company Geodis. In addition, identical target points, determine their coordinates and compare them with the coordinates obtained MOMAS system. And finally processed statistically derived coordinate differences.
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Fatigue Behaviour of AZ31 and AZ61 Magnesium Alloys
Gejdoš, Pavel ; Lukáč, Pavel (referee) ; Kohout, Jan (referee) ; Podrábský, Tomáš (advisor)
This doctoral thesis deals with the fatigue behaviour of AZ31 and AZ61 magnesium alloy casted by advanced methods of casting squeeze casting. Based on the regression functions and measured fatigue data were determined fatigue characteristics of these alloys. The work also extends into the area of fatigue cracks in the AZ31 alloy. Were measured fatigue crack propagation rate on modified cylindrical specimens. The paper also outlines the possibilities for describing the fatigue behaviour of AZ61 alloy in extremely low-cycle fatigue.
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Influence of asymmetry loading cycle on fatigue crack growth of alloy Inconel 625
Kander, Jan ; Kohout, Jan (referee) ; Věchet, Stanislav (advisor)
The main subject of this bachelor thesis was to evaluate influence of asymmetry of loading cycle on fatigue crack growth rate in a nickel-based superalloy Inconel 625. Experimental part of this thesis was carried out in Material and metallurgical research Ltd. Company in Ostrava, it’s main aim was to study the influences of loading cycles with parameter of asymmetry R = 0,1 and R = 0,7 on crack growth rate. Theoretical part deals with structure of nickel-based superalloys and fatigue crack growth rate.
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