This thesis describes a study of the influence of surface texturing on rolling contact fatigue of non-conformal contacts. The texture depth and density have been considered during experiments. It also presents the methodology and the procedure of creation of micro-dents on sample surfaces. Described results suggested that properly designed surface texturing should not necessarily increase the risk of fatigue failure of rubbing surfaces.

The thesis proposes a methodology for damage identification of thrust bearings using acoustic emission method. The work is the way of the hydraulic loading of specimens and thrust bearings with programmable settings severity and duration of load cycles during contact fatigue tests at stations Axmat. They are designed structural adjustment elements (waveguides) to capture the acoustic emission signal selected apparatus, including the modification of software to capture the data. At the described experiments is verified functionality of the circular test specimens and axial bearings . Part of this work is to propose a new methodology for identifying early stages of contact fatigue using a combination of diagnostic methods.

The Ph.D. thesis is focused on a surface degradation mechanisms under combined heat and mechanical load. The objects of examination are work rolls from hot rolling mill which suffer such a load. In first chapter, the hot rolling process, the design, the manufacturing process and present materials of work rolls are described. The state-of-the-art study of work roll surface degradation mechanisms – wear, oxidation, thermal and contact fatigue are described in the second chapter. The characterization, the formation, the mechanisms of progression and the effects of each surface degradation mechanism is described step by step. The state-of-the-art study of analytical and numerical models which are related to hot rolling process is described in third chapter together with their limitations and flaws. The next chapters contain design of an analytical, an optimized macroscopic and a microscopic model for study of the work roll stress state. The macroscopic and the microscopic model is based on finite element method and they are implemented in ANSYS Programming Design Language. The models are used to process several case study which are based on previous experimental work of the Heat transfer and fluid flow laboratory. The results from case studies specify and expand the knowledge of work roll stress state. The results show the portion of each loading factor on the whole stress state. In addition, time and depth depended distribution of stress state is presented. The results from macrosferic model illustrate the cause of spalling and a rupture of the work roll. The results from the microsferic model show the cause of creation of the to-surface-parallel cracks within carbides of high chromium irons. Last chapter summarized of all results gathered from case studies together with the goals for further research definition. The necessary steps for further cognition are stated. The thesis contains a large set of appendixes with deeper discussion of several related topics. These appendixes represent the one third of whole the thesis.

The thesis is focused on assessment of fatigue behaviour of austempered ductile iron with nodular graphite. Optimal period of transformation was determined based on the best combination of stress and strain characteristics established by tensile test. Cyclic response and low-cycle fatigue life were studied under both stress-control and longitudinal strain-control mode at room temperature. For both modes, shapes of cyclic hardening curves are dependent on stress amplitude. Cyclic deformation curves (CDC) were fitted by power regression function. Results were compared with CDC established by multiple step test in both modes with verification of the influence of cyclic creep (high stress levels, stress-control mode). Experimental data of S-N curves are in agreement with the Manson-Coffin and the Basquin law. Fatigue and cyclic parameters were compared. Fatigue life time in high-cycle fatigue region was determined. Experimental data were fitted by suitable regression functions. Regression parameters and fatigue limit were established by means of each regression function. Experimental data in low- and high-cycle fatigue regions were used to construct S-N curve and to determine relevant parameters. Discontinuity of experimental data was not observed. Low-cycle fatigue behaviour was predicted. Approximation of tolerance bands was realized in high-cycle and both high and low cycle fatigue regions.

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.

The thesis is focused on clarifying fatigue damage mechanisms and fatigue-creep damage mechanisms of MAR-M 247 and IN 713LC polycrystalline Ni-based superalloys. This thesis begins with basic information about nickel-based superalloys and their microstructure, followed by a description of fatigue and creep mechanisms and their mutual interaction. The next part contains experimentally obtained results describing the behavior of MAR-M 247 and IN 713LC superalloys under various sets of conditions. Three testing temperatures - 800, 900 and 950 °C were used for the measurement of fatigue properties under symmetrical loading cycle, because in the temperature range 800 – 950 °C, the mechanism of fatigue crack propagation of both superalloys should change from the originally crystallographic at "lower" temperatures (800 °C) to non-crystallographic at "higher" temperatures (950 °C). In addition the effect of processing technology on fatigue properties was studied on the superalloy IN 713LC. High-frequency cyclic loading (about 120 Hz) with high mean stress at elevated temperatures was applied to induce fatigue-creep interaction. The combined fatigue-creep loading was performed on the IN 713LC superalloy at 800 °C and on the MAR-M 247 superalloy at 900 °C.

Main topic of the thesis was to evaluate fatigue properties of the titanium alloy Ti-A13-V2,5, labelled by ASTM as Grade 9. Most attention was focused on fatigue behaviour of the alloy in the range of high cycle fatigue. Fatigue testing was realised to detect the fatigue properties and consequently to generate the Wöhler curve and the Haigh diagram. In addition to this, tension and bending tests were performed. Metallographic and fractographic analyses of fatigue fracture form part of the overview about material properties, which was accomplished by use of REM. Experimental part of the thesis was backed by the literature research. The first half of it contains a short summary of basic information about the titanium and its alloys, so as some chapters about the history and properties of titanium, the way of its production, classification of titanium alloys and its thermic treatment. The fatigue is thoroughly scrutinised in the second half of the background research. Here can also be found the information about the fatigue process, its stages, the fatigue life and the most significant attributes of the fatigue fracture. The last chapters of the thesis are dedicated to the alloy Ti-A13-V2,5 - being examined in the experimental part - so as to its fatigue properties. The main benefit of this thesis is the completion of the missing information concerning the fatigue behaviour of the alloy, which is – according to the literature research - generally not available.

The thesis is focused on assessment of fatigue behaviour of austempered ductile iron with nodular graphite. Optimal period of transformation was determined based on the best combination of stress and strain characteristics established by tensile test. Cyclic response and low-cycle fatigue life were studied under both stress-control and longitudinal strain-control mode at room temperature. For both modes, shapes of cyclic hardening curves are dependent on stress amplitude. Cyclic deformation curves (CDC) were fitted by power regression function. Results were compared with CDC established by multiple step test in both modes with verification of the influence of cyclic creep (high stress levels, stress-control mode). Experimental data of S-N curves are in agreement with the Manson-Coffin and the Basquin law. Fatigue and cyclic parameters were compared. Fatigue life time in high-cycle fatigue region was determined. Experimental data were fitted by suitable regression functions. Regression parameters and fatigue limit were established by means of each regression function. Experimental data in low- and high-cycle fatigue regions were used to construct S-N curve and to determine relevant parameters. Discontinuity of experimental data was not observed. Low-cycle fatigue behaviour was predicted. Approximation of tolerance bands was realized in high-cycle and both high and low cycle fatigue regions.

This doctoral thesis deals with the determination of the influence of plasma electrolytic oxidation (PEO) on fatigue behaviour of extruded AZ61 magnesium alloy in air and in the 3.5% NaCl solution. The coatings were formed in the silicate-phosphate electrolyte under pulsed current conditions at a frequency of 50 Hz. The influence of current density on coating formation was examined under current densities of 70, 130 and 200 mA cm-2 for different durations up to a maximum of 1800 s. 8 g dm-3 of KF were added to the electrolyte to study the influence of fluoride ions in plasma electrolytic oxidation. It is shown that fluoride ions inhibit localised oxidation in the initial stage of the process, associated with the secondary particles based on Al–Mn. The presence of fluoride also modified the sparking characteristics, decreased the rate of coating growth and changed the morphologies of the coatings. The influence of fluoride on the coating hardness, and the corrosion resistance of the alloy during exposure to salt spray, was negligible. Based on previous optimised PEO conditions, coatings formed under a current density of 130 mA cm-2 for 300 s in the electrolyte containing KF were chosen for fatigue testing. The high-cycle fatigue tests were carried out on cylindrical samples under a force controlled sinusoidal tension-tension cycle with asymmetry parameter R=0. The experimental data were fitted with Kohout & Věchet function. The fatigue limit of uncoated alloy in air for 107 cycles was determined at 145.4 MPa and the combination of PEO coating with chloride ions caused a reduction of ~55 %. Attention was paid to the fatigue crack initiation in different conditions of cyclic loading. The fracture surfaces underwent detailed fractography analysis including secondary crack observation on the gauge length. The contribution of Al–Mn particles were confirmed on the uncoated alloy in air and the presence of chloride ions were observed as another influential contributor to local corrosion attack. The cyclic loading caused spalling of the outer layer, and the multiple initiation was observed on PEO coated alloy, caused by cracks in the coating and stress transferring to the alloy.

Title: Changes in fitness levels and fitness parameters for water polo players during ATC 2012/2013 Objectives: The aim of the work determine the current performance through changes in competition and the transition period for players (n = 12, mean age 22.22 years + - 5, 6 years) water polo. Methods: To obtain a personal history of the probands was chosen method of qualitative structured interview with closed questions. From the basic anthropometrics values measured body height, weight and circuit parameters. Non-standard specific test for swimming biokinetic was at water polo players performed twice. The first test in the racing season (24th 3. 2013, 26th 3. 2013, 2nd 4. 2013), the second under the same conditions (10th 9. 2013), in a transitional period of annual training cycle (ATC) 2012/ 2013. The content of the selected non-standard specific test was compared test1 and test 2, which ran without the possibility of resting players were only interrupted by 40 seconds when tested probands carried leaps with throw up arms slightly bent at the elbows. This test was measured actual performance changes in ATC 2012/2013. Furthermore, fatigue was observed between test 1 and test 2 in the race and the transition period. During the trial, the parties all observed repeatedly drawn lactate. Results: All...