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Fracture behavior of welded polyolefin pipes
Mikula, Jakub ; Kučera,, Jaroslav (referee) ; Ševčík, Martin (advisor)
Cílem této diplomové práce je řešit problematiku poškozování svařovaných polyolefinových potrubí. Prezentovaná práce je zaměřena na numerické modelování kvazi-křehkého porušování, které je přímým důsledkem šíření creepové trhliny. Svařování polyolefinových potrubí vnáší do oblasti svaru nehomogenní rozložení materiálových vlastností a tvar svarového výronku způsobuje vznik geometrických koncentrátorů napětí. Posouzení těchto vlivů na životnost svarového spoje a výpočet polyolefinových potrubí je hlavním cílem této práce. V práci je uveden popis několika experimentálních testů (především CRB a PENT) k určení materiálových vlastností popisujících kinetiku trhliny. Výsledky práce jsou prezentovány pro polyetylenové potrubí (PE 100 110 x 6.3 SDR 17.6). Polyetylen je jeden z nejčastěji používaných materiálů právě v oblasti potrubních systémů. Prezentované výsledky práce mohou být použity i pro jiný polyolefinový materiál. Predikce životnosti polyolefinových potrubí je založena na lineárně elastické lomové mechanice (LELM) a koncepci faktoru intenzity napětí. Diplomová práce doplňuje tuto metodologii výpočtu životnosti o výpočet svařovaných polyolefinových potrubí z pohledu lomové mechaniky s náznakem možnosti budoucího výzkumu.
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Numerical modeling of crack propagation under conditions of LEFM
Mikula, Jakub ; Hutař, Pavel (referee) ; Ševčík, Martin (advisor)
The presented bachelor’s thesis deals with numerical modeling of crack propagation in general planar body. A user macro was created in APDL programming language for estimation of crack propagation direction and collection of data. Macro allows selection one of the four criteria intended to estimate the direction of the crack and the subsequent listing of the data into a text document. The calculation is based on the finite element method (FEM) using a commercial system ANSYS. The conditions of linear elastic fracture mechanics (LEFM) are expected during the calculation. The first part of this thesis describes the basic concepts of LEFM, including a description of mentioned criteria. The second part is devoted to the created macro. It also describes the algorithm and the necessary conditions for correct processing of data. A comparison with available published data or with experimental data gives a summary of the accuracy and utilization of created macro. In conclusion, the example of estimation of the residual life by different criteria is shown, as its other application.
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Comparison of freeware software for estimation of residual fatigue life of bodies
Hanáček, Jan ; Ševčík, Martin (referee) ; Pokorný, Pavel (advisor)
In the first part of this bachelor's thesis the fundamental laws of linear elastic fracture mechanics are described, especially state of stress in bodies with crack and stress intensity factor. Further, the propagation laws of fatigue crack are described and interaction effects of fatigue crack, especially retardation effects are explained. In the second part of this thesis the software NASGRO and AFGROW are described and compared. In the last part of this work the several examples are carried out to compare residual fatigue life obtained by no retardation approach and approach with consideration of retardation effects.
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Simulation of the HVS characterstics in Matlab
Ševčík, Martin ; Slanina, Martin (referee) ; Kratochvíl, Tomáš (advisor)
In theoretical part Diploma thesis deals with the model of human vision HVS (Human Visual System), which can be used for image quality assessment in TV technique area. It has been described calculations of selected JND (Just Noticeable Difference) metrics, used in evaluation of HVS. In practical part of the thesis it has been suggested and realized simulation model in Matlab, which may be used for evaluation of three JND metrics from color and grayscale images and evaluation in spatial a frequency domain. Results of JND models have been compared to another objective image quality evaluation metrics (MSE, NMSE, SNR and PSNR). For interpretation of dependencies it has been used images with different defined content.
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The influence of specimen dimensions on fatigue crack closure
Šebík, Marek ; Ševčík, Martin (referee) ; Poduška, Jan (advisor)
This study is focused on fatigue crack propagation, especially on plasticity-induced fatigue crack closure. The influence of specimen dimensions on fatigue crack closure is assessed by evaluation and consequent comparison of opening and closing stresses on two different fatigue specimen numerical models: compact tension specimen and center cracked plate tension specimen, using nonlinear material model. The numerical modeling of the phenomenon utilized finite element method. The models were created in Ansys programming language, APDL. The first part of the study deals with theoretical research of the subject. The second part consists of description and results of the numerical modeling.
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Modelling and Implementation of Control System for 3D Printer
Ševčík, Martin ; Pohl, Lukáš (referee) ; Jirgl, Miroslav (advisor)
The content of the thesis is the modeling and implementation of the CNC control algorithm. This master thesis contains the description of issues of computer-controlled machines, the research of interpolation algorithms for control CNC machines and the modeling of the selected control algorithm with motor S-curve shaped speed profiles and simulation of chosen algorithms with S-shaped speed profiles in Matlab & Simulink.
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Modelling and Implementation of Control System for 3D Printer
Ševčík, Martin ; Pohl, Lukáš (referee) ; Jirgl, Miroslav (advisor)
The content of the thesis is the modeling and implementation of the CNC control algorithm. This master thesis contains the description of issues of computer-controlled machines, the research of interpolation algorithms for control CNC machines and the modeling of the selected control algorithm with motor S-curve shaped speed profiles and simulation of chosen algorithms with S-shaped speed profiles in Matlab & Simulink.
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Preparedness of the selected area to participate in implementation of the tasks of civil protection during the release of hazardous chemicals.
ŠEVČÍK, Martin
This diploma thesis and its research deals with the preparedness of the population, pedagogues and representatives of municipal council, to participate in tasks of population protection during the leak of dangerous chemical substances. The work develops research from my Bachelor thesis from 2017, where was my task to verify preparedness of the integrated rescue system to deal with the leak of dangerous chemical substances. The aim of this diploma thesis was to find out, if is the selected area able to adequately respond to hazards arising from the leak of hazardous chemical substances. In order to assess preparedness, slightly different questionnaires were used, those questionnaires were answered by the residents of České Budějovice, teachers working at secondary schools in České Budějovice and representatives of the city and representatives of the South Bohemian Region. The results of the questionnaire survey are presented using descriptive statistics, interesting results are shown using graphs. A high degree of unpreparedness of respondents was found. According to the results of the questionnaire survey, some respondents may also behave dangerously in the events of leakage of hazardous chemicals. The contribution of this work should be increasing and improving awareness in this area. To this purpose, was created an information leaflet containing lot of important information, which was distributed to the population. The benefit which this work has already brought, is to alert representatives from city and region councils, as well as teaching staff, to improve their knowledge of hazardous substances. According to the feedback of several representatives, analyzes focusing the transport of dangerous substances can be expected in the near future. This work can be used as well as a source of information and can be used to compare it with other researches.
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Selected chemical substance and preparedness of integrated rescue system to these substance in selected area in South Bohemian region. (AMMONIA, CHLORINE, NATURAL GAS, BENZINE)
ŠEVČÍK, Martin
This bachelor thesis is focused on integrated rescue system, on it´s components and preparedness of this components to avert danger of dangerous chemical substances, specifically is this thesis focused on ammonia, chlorine, natural gas and benzine. Object of this thesis is find out whether the selected components of the integrated rescue system are able to adequately respond to the hazards resulting from the leakage of these substances. One of the partial objectives is the assessment of the preparedness and assessment of the material resources, because of these reasons, was used a questionnaire, which was filled in by the members of the Czech Republic integrated rescue system. The results of the questionnaire survey are displayed with using descriptive statistics. Results which were interesting are shown graphically. This work can be used as a source of information, as a learning tool or it can be used for compare changes in the preparedness of selected subjects after few years. Some kind of technical unprepardeness of police department and medical rescue service. The fire department was well prepared, not only because of the current material resources, but also because of constant modernization of their technology. The knowledge of all components is good enough to carry out its tasks, but there were also have been notised some mistakes in discipline of hazardous substances, which means possible health threats for rescuers. The work also includes possible solutions, for example creation of lectures, for members of the integrated rescue system which would be led by university teachers.
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