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Strength design of the truss construction
Rašovská, Hana ; Horníková, Jana (referee) ; Vrbka, Jan (advisor)
Bachelor thesis deals with strength, stress and strain analysis of the plain truss construction. The aim of the thesis is calculation the size of forces for two storage of the system with resultant suggestion of the cross- section geometry. The different position of the load is also considered. Further the influence of gravitational field of the Earth is reviewed as well as displacements in characteristic places, in construction is defined.
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Assesment of stress strain response during cyclic loading
Lehnert, Ondřej ; Slámečka, Karel (referee) ; Horníková, Jana (advisor)
This bachelor´s thesis is focused on assessment of data extracted from testing machine and establishment of cyclic stress-strain curve using peaks of saturated hysteresis loops. In this thesis before data analysis itself, is written down research study about general fatigue of material, then the study is focused on change of mechanical attributes, description of hysteresis loops and cyclic curve. After that follows the procedure of data analysis extracted from testing machine aimed to compare cyclic curve with tensile curve and its mathematical description.
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Stress and strength analysis of the bike frame and compliance assessment at selected construction places.
Prášil, Jiří ; Horníková, Jana (referee) ; Vrbka, Jan (advisor)
Purpose of this work was the realization of stress and strenght analysis of the bike frame with the help of the basic elasticity approach. At first I had to transfer this task from three-dimensional to two-dimensional and also to simplify to fulfill the beam conditions. I also focused on static safety of the construction. This static safety was solved for two loading modes. First one was define as the load, which cyclist can induce, when he is going on the direct road. Second one was defined as the load, which he can induce, when he is going up to the hill. I used for these calculations mathematical software such as Mathcad 14 or Maple 12, but also modeling software especially Autocad for establishing correct dimensions. At the end I checked the stress and strain analysis obtained by the basic elasticity approach with the solution performed making use of the ANSYS software code.
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Criteria of Multiaxial Fatigue Life
Blaha, Jakub ; Slámečka, Karel (referee) ; Horníková, Jana (advisor)
Bachelor’s thesis is about fatigue of materials and options of component’s lifetime determination during multiaxial cyclic loading. First it is described mechanism of initiation and grow of fatigue cracks, then the way of determination fatigue life during uniaxial loading and state of stress during multiaxial loading. Then multiaxial fatigue criteria for life time determination are presented. All criteria are based on critical plane and are divided into stress-based, strain-based and energy-based.
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Numerical simulation of crack propagation in ceramic composites in 3D
Svoboda, Josef ; Horníková, Jana (referee) ; Majer, Zdeněk (advisor)
The strength of materials such as glass and ceramics can be influenced by the environment (stress corrosion). Under applied stress defects (cracks) can grow sub-critically below fracture toughness K_Ic. The aim of this work was to develop a three-dimensional finite-element model to analyze the subcritical crack growth behavior of ceramic-based particulate composites. The maximum tangential stress criterion (MTS) was used to predict the direction of the crack propagation in the framework of linear elastic fracture mechanics. The modeled material was a Low Temperature Co-fired Ceramics (LTCC), containing alumina particles embedded in a glass matrix. The main aim of this work was to develop a 3D model describing the crack growth. Conclusions from this work can contribute to a better understanding of subcritical crack propagation in particle composites.
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The fatigue life of steel specimens under axial, torsional and combined axial-torsional loading
Mička, Jan ; Horníková, Jana (referee) ; Slámečka, Karel (advisor)
The master’s thesis deals with the fatigue life prediction under multiaxial cyclic loading. First, the fatigue process is discussed and the methods for fatigue life prediction under uniaxial and multiaxial loading are described. In the practical part, the accuracy of selected criteria is assessed based on experimental data obtained on cylindrical samples made of 1.2210 steel that were tested under synchronous symmetric axial-torsion loading. Application of criteria requires to determine the fatigue strength under pure axial and torsional loading.
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Description of creep crack propagation in electrofusion sockets for polymer pipes connection
Helešicová, Petra ; Horníková, Jana (referee) ; Trávníček, Lukáš (advisor)
The presented bachelor’s thesis deals with crack propagation by the slow crack growth mechanism in electrofusion sockets used for welding of polymer pipes. The thesis can be divided into several parts. First part presents a research on the topic of polymer pipes, materials used for their production, types of failures and ways of connecting including detailed description of the process of electrofusion welding with electrofusion sockets. Next part is focused on fracture mechanics that is used for the practical part of the thesis. The theory of linear elastic fracture mechanics and its stress-intensity approach are described. Different ways of obtaining the stress intensity factor, which is the main parameter used to describe the stress distribution at the crack tip, are presented. The practical part of the thesis focuses on numerical modelling of crack propagation through an electrofusion socket wall and calculating values of stress intensity factor in dependence on the crack length. The creation of the numerical model for the crack propagation simulation is described. The direction of propagation is evaluated using MTS criterion. The whole simulation is carried out by a parametric macro created using the APDL language. The main goal of the thesis is to describe the influence of the socket geometry or joint configuration changes on the stress intensity factor values and calculated lifetimes. The stress intensity factor functions for the modified configurations are compared to the original. At the end of the thesis, lifetime estimations of the electrofusion sockets are also calculated using the stress intensity factor functions and compared.
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Comparison of fatigue fracture criteria for uniaxial tension
Stolář, Jakub ; Šebek, František (referee) ; Horníková, Jana (advisor)
Bachelor’s thesis „Comparison of fatigue fracture criteria for uniaxial tension“ is focused on material fatigue and the possibilities of material service life aproximation for uniaxial tension. Research study of material fatigue and fatigue fracture criteria is stated in the first part of the thesis. In the second part, experimentally measured data are processed and application suitability of particular fatigue fracture criteria is assessed while using the research study theoretic findings.
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Influence of torsional pre-strain on fracture characteristics under tensile loading
Kupka, Oldřich ; Majer, Zdeněk (referee) ; Horníková, Jana (advisor)
The diploma thesis is about the influence of torsional pre-strain on fracture characteristics under tensile loading of steel 11 375. Plastic strain in the cross-section of tested specimen is caused by torsional pre-strain. Plastic strain causes a different response of a material to tensile loading. A smooth tensile test specimen and tensile test specimen with a notch are examined. The research part of thesis describes tensile and torsional tests according to regular standarts. The nonlinearities considered in computational models are also described, followed by a description of material models in the software Ansys, which is used to create the computational model. Mechanisms of failure, the importance of stress triaxiality and the construction of triaxiality space are also introduced to a reader. The first experiment is about a tensile test of steel 11 375. The stress-strain curve obtained by the tensile test will be used as input in computational modelling. The aim of computational modelling is the determination of torsional pre-strain, that causes plastic strain in a tested specimen. The true stress field, true strain field and points of triaxiality space are determined by computational models. During the second experiment, tensile test specimens are torsioned according to outputs of computational models, followed by a tensile load to fracture. The main output of the experiment is fracture engineering strain. Finally, the stress-strain curves of computational models are also compared with experimental measurements.
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