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Fatigue crack front shape estimation
Zouhar, Petr ; Klusák, Jan (referee) ; Hutař, Pavel (advisor)
The presented master’s thesis deals with fatigue crack front shape estimation. The aim of this thesis is to create an iterative process leading to the real fatigue crack front shape. Thesis is solved using finite element method. The work is divided into two logical parts. The first part of the thesis describes the basic concepts of linear elastic fracture mechanic (LEFM), methods used for estimation of stress intensity factor and stress singularity exponent. The first part further describes some phenomenon’s accompanying the mechanism of fatigue crack growth as for example crack tip curving and crack closure. In the second part of the thesis there is studied an affect of the free surface on the fracture parameters, especially the affected distance from the free surface is determined. Based on the assumption of a constant stress intensity factor and stress singularity exponent along the crack front, an iterative process leading to fatigue crack front shape is presented. The accuracy of the result is discussed by comparing of obtained crack front shapes with experimental data at the end of the thesis.
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Prediction of shotcrete behavior applying elastoplastic material model
Kejík, Vít ; Miča, Lumír (referee) ; Chalmovský, Juraj (advisor)
This work is focused on the application of advanced elasto-plastic material model intended for shotcrete. Spatial mathematical models of two laboratory tests are created, where this model is used. The first test is a three-point bending concrete specimen. Next, the behavior of the material is analyzed, in which input parameters are entered. Consequently, two reverse analyzes of the available data are analyzed where a match between prediction and measurement can be obtained. The second test is a modified tensile test, where is describe the material behavior in changing of input parameters. Subsequently, reverse data analysis is created, where an acceptable match between prediction and measurement is possible. In every study, the stress waveform in the fracture process zone is analyzed to more detail.
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Evaluation of fracture tests of selected concrete specimens
Součková, Markéta ; Lehký, David (referee) ; Keršner, Zbyněk (advisor)
This bachelor thesis deals with evaluation of fracture tests of selected concrete specimens. It is divided into two parts: theoretical and practical. The theoretical section describes fracture parameters, three point bending test and effective crack model. It explains evaluation process of the expriments step by step, too. The practical part contains charts with the resulting values of fracture parameters. The StiCrack software was used for analysis of fracture tests. The result of this thesis is comparison of influence the thength classes of concrete, age of specimens and place of ripen on the values of fracture parameters.
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Prediction of shotcrete behavior applying elastoplastic material model
Kejík, Vít ; Miča, Lumír (referee) ; Chalmovský, Juraj (advisor)
This work is focused on the application of advanced elasto-plastic material model intended for shotcrete. Spatial mathematical models of two laboratory tests are created, where this model is used. The first test is a three-point bending concrete specimen. Next, the behavior of the material is analyzed, in which input parameters are entered. Consequently, two reverse analyzes of the available data are analyzed where a match between prediction and measurement can be obtained. The second test is a modified tensile test, where is describe the material behavior in changing of input parameters. Subsequently, reverse data analysis is created, where an acceptable match between prediction and measurement is possible. In every study, the stress waveform in the fracture process zone is analyzed to more detail.
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Fatigue crack front shape estimation
Zouhar, Petr ; Klusák, Jan (referee) ; Hutař, Pavel (advisor)
The presented master’s thesis deals with fatigue crack front shape estimation. The aim of this thesis is to create an iterative process leading to the real fatigue crack front shape. Thesis is solved using finite element method. The work is divided into two logical parts. The first part of the thesis describes the basic concepts of linear elastic fracture mechanic (LEFM), methods used for estimation of stress intensity factor and stress singularity exponent. The first part further describes some phenomenon’s accompanying the mechanism of fatigue crack growth as for example crack tip curving and crack closure. In the second part of the thesis there is studied an affect of the free surface on the fracture parameters, especially the affected distance from the free surface is determined. Based on the assumption of a constant stress intensity factor and stress singularity exponent along the crack front, an iterative process leading to fatigue crack front shape is presented. The accuracy of the result is discussed by comparing of obtained crack front shapes with experimental data at the end of the thesis.
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Evaluation of fracture tests of selected concrete specimens
Součková, Markéta ; Lehký, David (referee) ; Keršner, Zbyněk (advisor)
This bachelor thesis deals with evaluation of fracture tests of selected concrete specimens. It is divided into two parts: theoretical and practical. The theoretical section describes fracture parameters, three point bending test and effective crack model. It explains evaluation process of the expriments step by step, too. The practical part contains charts with the resulting values of fracture parameters. The StiCrack software was used for analysis of fracture tests. The result of this thesis is comparison of influence the thength classes of concrete, age of specimens and place of ripen on the values of fracture parameters.
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Numerical analysis of a surface crack propagation in protective layers
Majer, Zdeněk
The paper contains a numerical analysis of a surface crack propagation in an elastic surface layer. It was analysed an influence of elastic material parameters of both system components, initial length and orientation of crack on fatigue crack propagation direction. The typical behaviour of crack propagation in thin layers was described. The finite element method for determination of the direction of the farther crack propagation was used.
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