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Safety of technological systems
Jiříček, Petr ; Pavlík, Josef (referee) ; Hammer, Miloš (advisor)
The work deals with the safety of technological systems and can be divided into two main thematic units. The attention in the first theoretic unit is paid to aspects that affect the safety of technological systems during their technical life. It describes, together with elementary norms and acts solving the products safety, the most important principles for creating and analysing the safety. It clarifies the origin of company’s risk management, part of its quality management, mentions the faults in which products can be found and also describes the failures which have the biggest effect on these faults and of course on the safety too. Attention is further paid to the reliability analysis, as the tool that helps to create the products safety in the pre-manufacturing phase and also to technical diagnostic, as the tool to keep the safety in after-manufacturing phase. The second practical unit arithmetically analyses the safety of two high-voltage transformers. For that it was used the database of real operation numerical values that were gained during diagnostic investigations on these transformers. In addition it describes mentioned diagnostics methods and gives the new procedure for analyse of transformers’ safety by criteria matrix and weighted sum approach. The main contribution of the work can be considered the checkout and the evaluation of this procedure for use in elaboration of high-voltage transformers diagnostic values for analyzing their safety.
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Diagnostic of System Reliability
Bábek, Tomáš ; Pohl, Jan (referee) ; Havlíková, Marie (advisor)
This thesis is oriented to the reliability theory and diagnostics. It involves brief explanation of terms that exists in a branches of technical devices reliability. The next part contains determining the reliability indexes, calculations of probabilities and statistics for electronic devices. I do mention the different methods of reliability diagnostics. The three most used of them are described. First of them is the reliability block model. By this I describe the serial reliability model, the parallel reliability model and the combination of them. Using this method is the simple way to show how each component affects reliability of the whole system. The second method is FMEA (Failure Mode and Effects Analysis) which is used mostly in the begining of the system designing. The third method is FTA (Fault tree analysis) which is one of the classic deductive methods. The FTA method is a graphical reliability model of a given system. By the end of this thesis, process of calculating the failure probability and the other reliability indexes of a given komponent (preamplifier with operational amplifier) is shown.
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Systems Reliability Analysis using Monte Carlo Approach
Kučírek, Vojtěch ; Havlíková, Marie (referee) ; Jirgl, Miroslav (advisor)
Master’s thesis is focused on the technical systems reliability analysis. The first part of the thesis contains the description of the most commonly used reliability parameters and random variable probability distributions. Reliability of a human operator is described in the separate chapter. In the next part of the thesis are mentioned different types of reliability diagrams and methods of reliability analysis. Reliability analysis using Monte Carlo approach is described in the extra chapter. In the thesis are described several software tools, which can be used for systems reliability analysis. Design of PLC system with a human operator is done in the thesis. Reliability analysis using Monte Carlo approach is done on the designed PLC system. Results of Monte Carlo approach are compared with analytically calculated values and with values from reliability software.
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Reliability analysis of the hip joint endoprosthesis ceramic head
Málek, Michal ; Janíček, Přemysl (referee) ; Fuis, Vladimír (advisor)
This diploma thesis deals with probability of fracture ceramic head of total hip endoprosthesis during tests by the standard ISO 7206-5. In the first part is made stress analysis with method of finite elements in program ANSYS. Six types of ceramic head with different geometry was analysed for ideal geometry of head and shaft, and also for shape imperfections from nominal conical shaft and head. The final values of principal stress from stress analysis were entry values for the second part – probability of fracture analysis. Weibull weakest-link theory was applied, namely 3-Parameter and 2-Parameter Weibull distribution.
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STOCHASTIC CRACK PROPAGATION MODELLING USING THE EXTENDED FINITE ELEMENT METHOD
Nešpůrek, Lukáš ; Novák, Drahomír (referee) ; Hutař, Pavel (referee) ; Anthony Nouy, PhD., HDR (referee) ; Knésl, Zdeněk (advisor)
Tato disertační práce vychází z výzkumu v rámci francouzsko-českého programu doktorátu pod dvojím vedením na pracovišti Institut français de mécanique avancée v Clermont-Ferrand a na Ústavu fyziky materiálu AV v Brně. Úvodní výzkumný úkol na brněnském pracovišti se zabýval numerickou analýzou pole napětí v okolí čela trhliny v tenké kovové fólii. Zvláštní pozornost byla zaměřena na vliv speciálního typu singularity v průsečíku čela trhliny s volným povrchem. Těžiště disertační práce spočívá v numerickém modelování a stochastické analýze problémů šíření trhlin se složitou geometrií v dvojrozměrném prostoru. Při analýze těchto problémů se dříve zřídka používaly numerické metody, a to z důvodu vysoké náročnosti na výpočtový čas. V této disertaci je ukázáno, že aplikací moderních metod numerické mechaniky a vhodných technik v analýze spolehlivosti lze tyto problémy řešit s pomocí numerických metod i na PC. Ve spolehlivostní analýze byla využita lineární aproximační metoda FORM. Pro rychlost šíření trhlin se vycházelo z Parisova-Erdoganova vztahu. Pro parametry tohoto vztahu byl použit dvourozměrný statistický model, který postihuje vysokou citlivost na korelaci obou parametrů. Mechanická odezva byla počítána rozšířenou metodou konečných prvků (XFEM), která eliminuje výpočetní náročnost a numerický šum související se změnou sítě v klasické metodě konečných prvků. Prostřednictvím přímé diferenciace bylo odvozeno několik vztahů pro derivace funkce odezvy, čímž se dosáhlo lepší numerické stability a konvergence spolehlivostní analýzy a výrazného zkrácení doby výpočtu. Problém zatížení s proměnou amplitudou byl řešen aplikací transformace zatížení metodou PREFFAS. Využití distribuce výpočtů v síti PC umožnilo další zrychlení analýzy.
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The probabilistic solution of dike breaching due to overtopping
Alhasan, Zakaraya ; Fošumpaur, Pavel (referee) ; Šoltész,, Andrej (referee) ; Říha, Jaromír (advisor)
Doctoral thesis deals with reliability analysis of flood protection dikes by estimating the probability of dike failure. This study based on theoretical knowledge, experimental and statistical researches, mathematical models and field survey extends present knowledge concerning with reliability analysis of dikes vulnerable to the problem of breaching due to overtopping. This study contains the results of probabilistic solution of breaching of a left bank dike of the River Dyje at a location adjacent to the village of Ladná near the town of Břeclav in the Czech Republic. Within thin work, a mathematical model describing the overtopping and erosion processes was proposed. The dike overtopping is simulated using simple surface hydraulics equations. For modelling the dike erosion which commences with the exceedance of erosion resistance of the dike surface, simple transport equations were used with erosion parameters calibrated depending on data from past real embankment failures. In the context of analysis of the model, uncertainty in input parameters was determined and subsequently the sensitivity analysis was carried out using the screening method. In order to achieve the probabilistic solution, selected input parameters were considered random variables with different probability distributions. For generating the sets of random values for the selected input variables, the Latin Hypercube Sampling (LHS) method was used. Concerning with the process of dike breaching due to overtopping, four typical phases were distinguished. The final results of this study take the form of probabilities for those typical dike breach phases.
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Systems Reliability Analysis Using Monte Carlo
Approach
Kučírek, Vojtěch
This paper is focused on the systems reliability analysis. In the first part of the paper, the reliability block diagrams and the most commonly used reliability parameters are described. Next part of the paper is focused on the Monte Carlo approach used in systems reliability analysis. In the last part of the paper, digital multimeter reliability analysis using Monte Carlo approach is made.
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Systems Reliability Analysis using Monte Carlo Approach
Kučírek, Vojtěch ; Havlíková, Marie (referee) ; Jirgl, Miroslav (advisor)
Master’s thesis is focused on the technical systems reliability analysis. The first part of the thesis contains the description of the most commonly used reliability parameters and random variable probability distributions. Reliability of a human operator is described in the separate chapter. In the next part of the thesis are mentioned different types of reliability diagrams and methods of reliability analysis. Reliability analysis using Monte Carlo approach is described in the extra chapter. In the thesis are described several software tools, which can be used for systems reliability analysis. Design of PLC system with a human operator is done in the thesis. Reliability analysis using Monte Carlo approach is done on the designed PLC system. Results of Monte Carlo approach are compared with analytically calculated values and with values from reliability software.
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The probabilistic solution of dike breaching due to overtopping
Alhasan, Zakaraya ; Fošumpaur, Pavel (referee) ; Šoltész,, Andrej (referee) ; Říha, Jaromír (advisor)
Doctoral thesis deals with reliability analysis of flood protection dikes by estimating the probability of dike failure. This study based on theoretical knowledge, experimental and statistical researches, mathematical models and field survey extends present knowledge concerning with reliability analysis of dikes vulnerable to the problem of breaching due to overtopping. This study contains the results of probabilistic solution of breaching of a left bank dike of the River Dyje at a location adjacent to the village of Ladná near the town of Břeclav in the Czech Republic. Within thin work, a mathematical model describing the overtopping and erosion processes was proposed. The dike overtopping is simulated using simple surface hydraulics equations. For modelling the dike erosion which commences with the exceedance of erosion resistance of the dike surface, simple transport equations were used with erosion parameters calibrated depending on data from past real embankment failures. In the context of analysis of the model, uncertainty in input parameters was determined and subsequently the sensitivity analysis was carried out using the screening method. In order to achieve the probabilistic solution, selected input parameters were considered random variables with different probability distributions. For generating the sets of random values for the selected input variables, the Latin Hypercube Sampling (LHS) method was used. Concerning with the process of dike breaching due to overtopping, four typical phases were distinguished. The final results of this study take the form of probabilities for those typical dike breach phases.
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