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Investigation of deformation mechanisms in Mg-Gd alloys
Szabóová, Andrea ; Mathis, Kristián (advisor) ; Drozdenko, Daria (referee)
Title: Investigation of deformation mechanisms in Mg-Gd alloys Author: Andrea Szabóová Department: Department of Physics of Materials Supervisor: doc. RNDr. Kristián Mathis, DrSc. Abstract: In the present work, the deformation behavior of magnesium-gadolinium binary alloys was investigated. Dependence on the concentration of Gd and deformation temperatures was studied. Extruded samples had relatively strong initial texture. Compression tests were done at room temperature and 200řC. Simultaneously with deformation acoustic emission was recorded. Data from acoustic emission was analyzed with advanced statistical methods. Results of the combination of these two experimental methods indicated that at the beginning of the deformation twinning is the dominant mechanism. In the following stage of plastic deformation non-basal slip systems became the governing deformation mechanism. With higher content of Gd the size of twins decreases as a result of the decreased mobility of twin boundaries caused by solute atoms. At higher temperatures twinning activity was increasing. In addition, results were confirmed by optical light and scanning electron microscopy. Keywords: magnesium alloy, deformation tests, acoustic emission, microscopy
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Study of advanced high strength magnesium alloys by in situ techniques
Fekete, Klaudia ; Dobroň, Patrik (advisor) ; Lejček, Pavel (referee) ; Mayama, Tsuyoshi (referee)
The aim of the present doctoral thesis was to reveal the active deformation mechanisms in novel high strength magnesium (Mg) alloys using advanced in-situ techniques with high time and space resolutions. The deformation behavior of two extruded Mg-LPSO alloys with a different volume fraction of the long-period stacking ordered (LPSO) phase was investigated in tension and compression at room temperature and in compression at 200 řC, 300 řC, and 350 řC. In order to support the results obtained by in-situ acoustic emission and synchrotron diffraction methods, detailed microstructure investigation was provided by transmission and scanning electron microscopy, particularly the backscattered electron imaging and electron backscatter diffraction technique were used. The results indicate that both temperature and the LPSO phase content significantly influence the plasticity of the magnesium matrix, particularly they affect the activation of extension twins and non-basal slip. Moreover, both parameters have a high impact on the formation of the deformation kinks in the LPSO phase. Keywords: Mg-LPSO alloys, deformation mechanisms, acoustic emission, synchrotron diffraction, in-situ methods.
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Influence of dynamic loading on the contact fatigue characteristics of bearing material
Hložek, Jiří ; Hutař, Pavel (referee) ; Mazal, Pavel (advisor)
This thesis deals with the study of sudden step changes observed in model testing of standard bearing steel 100Cr6. Methodology of experiments with step change of load is proposed and applied in measurements. Three complete series of experiments were conducted, and rating life was determined for each loading trend. Based on the experiments carried out, it was found that the selected steel is able to withstand the sudden step of load changes, despite the fact that it is not material of choise for this type of load. Part of this work was to verify functionality of the innovated test stations AXMAT with modern diagnostics and a new control system, and also of the hydraulic variant of AXMAT, which allows to remotely derive dynamic loading of the test sample.
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Monitoring and Analysis of Corrosion of Reinforcing Steel in Reinforced Concrete Elements and Structures Using the Acoustic Methods
Timčaková, Kristýna ; Semerák,, Petr (referee) ; Medveď,, Igor (referee) ; Vaněrek, Jan (referee) ; Chobola, Zdeněk (advisor)
The dissertation thesis deals with the study of non-destructive acoustic methods as instruments for monitoring and analysing corrosion of reinforcing steel in reinforced concrete elements. Four acoustic methods were selected for this task - the impact-echo method, the nonlinear acoustic spectroscopy method, the acoustic emission method, and the ultrasonic pulse velocity method. To verify the functionality of these methods, testing was carried out on three sets of reinforced concrete samples that had been exposed to the effects of sodium chloride, which corroded the embedded steel reinforcement in these samples. Suitable parameters were proposed for individual acoustic methods to monitor corrosion of the reinforcements. In addition, experiments were designed to demonstrate the ability of the selected acoustic methods to reveal the corrosion of steel reinforcement and its influence on the concrete matrix and to assess the condition of the degraded elements and structures. The analysis of the measurement results based on their comparison shows the advantages and disadvantages of the individual methods and of their practical applications. To verify the results, correlation with common methods that are currently used for the study of corrosion was carried out and included for example the electrical resistivity measurement of the reinforcement and simultaneous monitoring of the sample surface using a confocal microscope to record the development of microcracks during the degradation.
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Using Acoustic Emission for aircraft structure monitoring
Krasavin, Taras ; Juračka, Jaroslav (referee) ; Jebáček, Ivo (advisor)
This thesis deals with the theoretical and practical part of the phenomenon of acoustic emission. The thesis examined the theoretical foundations of this phenomenon and also described the equipment that was used in the laboratory of VUT in Brno to perform measurements. Then measurements and their analysis were described. Several possible errors that occurred during the work on the thesis were also described. Error description is the basis for error-free laboratory testing and for improving the quality of laboratory testing.
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Investigation of deformation mechanisms in textured magnesium alloy
Dittrich, Jan ; Minárik, Peter (advisor) ; Lukáč, Pavel (referee)
Název práce: Studium deformačních mechanism· v hořčíkové slitině s texturou Autor: Jan Dittrich Katedra: Katedra fyziky materiál· Vedoucí bakalářské práce: RNDr. Peter Minárik, PhD., Katedra fyziky materiál· Abstrakt: Předložená práce se zabývá studiem deformačních mechanism·, zá- visejících na orientaci vzork· v·či p·vodní textuře válcované hořčíkové slitiny, pomocí pokročilých in-situ i ex-situ metod. Během deformačních zkoušek, které byly prováděny v tlaku a v tahu, byla současně zaznamenávána akustická emise. Mikrostruktura deformovaných vzork· poté byla zkoumána metodami optické mi- kroskopie a difrakce zpětně odražených elektron·. V práci byla zjištěna výrazná závislost mechanických vlastností a aktivovaných deformačních mechanism· na orientaci vzork· v·či zjištěné bazální textuře válcovaného plechu hořčíkové sli- tiny AZ31. Dále byla ustanovena souvislost mezi základními parametry akus- tické emise a aktivovanými deformačními mechanismy. Rovněž byla pozorována a objasněna asymetrická odezva akustické emise při deformaci tlakem a tahem, související s rozdílným vývojem mechanického dvojčatění v pr·běhu plastické deformace. Klíčová slova: hořčíkové slitiny, deformace, dvojčatění, akustická emise, EBSD
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Investigation of basic deformation mechanisms of magnesium alloys by means of advanced in-situ methods and theoretical modeling
Čapek, Jan ; Mathis, Kristián (advisor) ; Landa, Michal (referee) ; Šiška, Filip (referee)
The work is focused on developing testing methods for investigating of the deformation mechanisms of magnesium alloys. The work involves the measurement of in-situ acoustic emission and neutron diffraction and comparison to the theoretical models. Mg + 1wt.% Zr alloy was selected for investigation of the compression - tension asymmetry. Advanced analysis of acoustic emission and neutron diffraction data revealed activation of different slip systems during deformation. Moreover, the different evolution of twinning was explained. The same methods were used to investigate the aluminum influence on deformation mechanisms. The hardening of basal slip and twinning and increasing importance of prismatic slip was observed.
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Význam nedestruktivního zkoušení v oblasti hodnocení kvality svarů během procesu
Koucký, Miloslav
The diploma thesis The significance of nondestructive testing in the area of evaluation of the welds quality during the process is focused on the area of creating a material weld joint that cannot be disassembled. In the theoretical part the area of fusion welding, methods of fusion welding and defects of weld joints are analysed. Assessment of current practice of verification of the weld joint quality using nondestructive testing is analysed, too. In the experimental part of the diploma thesis progressive examination for assessing the weld joint quality is suggested from the view of making an expert as-sessment. The suggested method of evaluating the making of welds is also verified in an experimental way and the gained results of the performed measurement are compared with the existing method of determining the weld quality. In the final part of the diploma thesis economical assessment of the benefit of the suggested method and its incorporation into the qualification of an expert engineer is carried out.
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