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Fatigue life prediction models
Hurta, Filip ; Vaněk, František (referee) ; Sladký, Martin (advisor)
Evaluation of fatigue is essential for determining operational capabilities of mechanical parts. Principles of material fatigue are discussed in this bachelor thesis. Most attention is paid to linear elastic fracture mechanics and variable amplitude loading. There are mathematical models, that describe conditions in the center of damaging. In the text there are described chosen models based on fracture mechanics. On basis of the conducted research, a computer program was developed, solving a crack growth in a specimen, depending on the defined loading. This program does not consider interaction effects during the loading sequence. Program output validation was performed by comparison of given results with the calculation and tests results from the literature. The data correlate with the non-interaction predictions, but comparison with the reality demonstrates the importance of interaction effects in complex loading.
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Corrosion of Aircraft Structures
Poláček, Juraj ; Juračka, Jaroslav (referee) ; Katrňák, Tomáš (advisor)
Presented bachelor's thesis deals with the corrosion attack of aircraft structures and their influence on the mechanical properties of individual parts of aircraft structures. The research part of the thesis describes the principles of corrosion attack formation and the influence of aggressive envi- ronments on their formation and development. The influence of aggressive environments is demonstrated through corrosion tests. The thesis maps the most commonly used materials in the aerospace industry. At the same time, it assigns specific materials to typical locations of aircraft structures. Through information and assistance with LOM Prague company, the thesis identifies and displays the most common corrosion-prone areas. Additionally, possible hazards arising from corrosion in specific locations of aircraft structures are described. The output of the thesis presents options for corrosion protection. This is especially the process of anodization, surface treatments, maintenance and appropriate material design in the development of aircraft structures. Due to the extensive use of the anodization process and surface treatments, an analysis was conducted to assess their impact on the mechanical properties of aluminium alloy 6061.
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Potential Causes Of Afternoon Tiredness. Fatigue and exhaustion in the context of contemporary art.
Zentková, Barbora ; Kralović,, Ján (referee) ; Hrončeková, Ivana (referee) ; Rathouský, Luděk (advisor)
The dissertation focuses on the topic of fatigue and exhaustion, which I consider to be one of the characteristic features of today's society. The imperative of constant productivity and high workload is written into all areas of our lives, not excluding the non-work sphere. My intention is to explore and name the main socio-economic causes and consequences of fatigue and exhaustion through the lens of contemporary art, and to introduce readers to the work of domestic and foreign authors who respond in a particular way to the challenges posed by the current neoliberal system. My aim is also to try to present a number of inspiring artistic approaches that can also serve as certain starting points and tools for rethinking established practices and offer concrete solutions to prevent the imminent collapse. At the same time, I have been working on the theme of fatigue and exhaustion for a long time in my collaborative artistic practice with Julia Gryboś. The theoretical part of the dissertation is therefore at the same time an effort to name and define the research carried out within the framework of its own artistic results.
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Návrh silového členu simulátoru zátěže pro dlouhodobé zkoušky VTG aktuátoru
VANĚK, Daniel
The topic of diploma thesis is focused on the design of the life of the power member of the preparation with springs (the load simulator). The preparation is used for long-term testing of VTG (Variable Turbinen Geometrie) actuators. The diploma thesis follows the author's bachelor's thesis (Vaněk, 2019). The theoretical part is focused on the fatigue of the material, the geometry of the used springs, the decomposition of the test profile using the Rain flow method and the Matlab (interactive software). The practical part of that thesis deals with the analysis of the test profile, the calculation of the accumulation of damage and the statistical evaluation of the service life of the used springs.
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High Cycle Fatigue Modelling in ANSYS Workbench
Zoubek, Vojtěch ; Řehák, Kamil (referee) ; Dlugoš, Jozef (advisor)
This diploma thesis deals with the extension of the solution of high-cycle material fatigue in Ansys program. The goal of the thesis is creation own algorithm for evaluation of FEA results and overcoming the existing built-in tool. Thesis is divided into theoretical and practical part. In theoretical part, there was created literary research about material fatigue and current solution options. Practical part introduces own algorithm of evaluation.
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Advance evaluation of fatigue resistance of selected construction materials
Benešová, Anna ; Květoň, Josef (referee) ; Seitl, Stanislav (advisor)
This thesis deals with the analysis of S–N curves of models according to Basquin, Kohout and Věchet and Castilla–Canteli using Weibull and Gumbel solution. These curves are interpolated by measured data of cyclically loaded civil engineering materials like concrete and steel. For each material, the accuracies of individual models are determined and in the conclusion, the suitability or unsuitability of individual models for selected materials is compared and evaluated.
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Numerical Modelling of Fatigue Crack Closure
Oplt, Tomáš ; Růžička, Milan (referee) ; Horníková, Jana (referee) ; Hutař, Pavel (advisor)
This Ph.D. thesis was written under the supervision of Assoc. prof. Pavel Hutař, Ph.D., and Assoc. prof. Luboš Náhlík, Ph.D. The thesis is focused on the effect of plasticity induced crack closure, its characteristic and ways of numerical modelling. Premature fatigue crack closure has a significant effect on the fatigue crack propagation rate and therefore on the residual lifetime of a structure. A three-dimensional numerical model allows a detailed look at the stress and strain distribution along the crack front, and particularly it allows a local description of parameters along the crack front which governs the fatigue crack propagation rate. In the first part of the thesis, the study is focused on the influence of a singular stress field at the vicinity of the free surface on the crack front curvature without crack closure being involved. In the second part, a numerical model in 2D of plasticity induced crack closure was created and verified by experimental results. In the final part, a 3D numerical model is used to describe the influence of the crack closure on its fatigue propagation rate and explains typical crack front curvature. The suggested technique allows quantitative accuracy improvement of numerical simulation of the fatigue crack propagation and therefore, more reliable estimation of the residual lifetime of the cracked structure.
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Increasing the fatigue life of the firearm firing pin using the explicit solver
Adamec, Tomáš ; Petruška, Jindřich (referee) ; Šebek, František (advisor)
Firing pin is a critical component in terms of firearm function. Tip of firing pin can break off due to repeated impact loading, which results in malfunction of the whole firearm. This master's thesis aims to propose changes in geometry of the firing pin so that new firing pin will be more durable against fatigue failure. Geometry and characteristics of the original firing pin are provided by company Česká zbrojovka, a.s. To determine the amount of fatigue damage for specific configuration of firing pin, computational model, which simulates impact loading of the firing pin during dry fire, is created. Finite element method with explicit formulation is used for the calculation. Parameters of geometry, which are assumed to have highest influence on fatigue life, are chosen based on the analisys of the original firing pin. These parameters are changed in further calculations, resulting in new configuration of the firing pin, which is approximately 15 % more durable against fatigue failure.
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Fatigue evaluation methods for pressure equipment utilising numerical analysis results
Boleloucký, Václav ; Lošák, Pavel (referee) ; Létal, Tomáš (advisor)
Diplomová práce se zabývá hodnocením únavové životnosti v okolí konstručního uzlu tlakové nádoby, kde vzniká výrazná koncentrace napětí a je zde předpoklad primárního vlivu na únavu materiálu. Konkrétně se jedná o místo přechodu kontrolního otvoru do pláště analyzovaného zařízení. Práce obsahuje teoretickou a praktickou část. V teoretické části jsou představeny pojmy a metody hodnocení, související s danou problematikou. Na základě těchto metod je provedena analýza konstrukčního uzlu tlakové nádoby. Analýza je provedena metodou konečných prvků na skořepinovém a objemovém modelu nádoby v softwaru ANSYS Workbench, její výsledky dále zpracovány a vyhodnoceny dle aktuálního návrhu úpravy evropské harmonizované normy EN 13445--3, kapitoly 18. Výsledky analýz jsou hodnoceny v závěru práce.
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Low cycle fatigue research and application in nuclear industry
Sehnal, Dominik ; Kuželka, Jiří (referee) ; Hůlka, Jiří (advisor)
Fatique life extension of nuclear powerplants lies in the search for project reserves. This work deals with the evaluation of low-cycle fatigue of nuclear installations of the VVER type and the assessment of the influence of the computational model level. Fatigue tests of austenitic steel using optical method of digital image correlation for which the evaluation procedure is designed and used is performed. Selected model of plasticity with kimenatic (Chaboche) and combinated hardening (Chaboche, Voce) are calibrated from the obtained data. Subsequently, the durability of the test specimen is determined by computational modeling for different material models. From the comparison of the results of fatigue tests with the calculation, the material models suitable for the description of fatigue life and their validity are determined.
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