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Initiation of stable crack propagation of selected building composites
Majtánová, Romana Viktória ; Veselý, Václav (referee) ; Keršner, Zbyněk (advisor)
The purpose of my bachelor’s thesis is study of the effects of fibres in normal-weight concrete and light-weight concrete. Specimens were prepared from concrete with polypropylene fibres FORTA FERRO of three different lengths – 19, 38 and 54 mm – and also reference concrete (without fibres) was prepared. This thesis contains gradual evaluation of fracture tests on specimens from mentioned materials. The used fracture test was a three–point bending fracture test on beams with a central notch. From the measured load–deflection in the middle of span and load–crack mouth opening displacement diagrams were determined values of modulus of elasticity, unstable fracture toughness, initiation part of fracture toughness and also load level for beginning of stable crack propagation composites. For determination was used „double–K“ fracture model. For illustration is described evaluation using the effective crack model.
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Fracture tests of selected specimens with special aggregates: experiments and numerical simulation
Majda, Tomáš ; Malíková, Lucie (referee) ; Keršner, Zbyněk (advisor)
The diploma thesis deals with selected fracture tests and evaluation of fracture parameters of cement-based composite. One part of the thesis deals with cement-based composite with glass spherical aggregate of a single fraction of 2 mm. After production, the beams with dimensions of 20×40×200mm exposed to temperatures in the range from 100 to 1000 °C for one hour. Using the non-destructive ultrasonic pulse method, the degree of damage caused by termal load was determined. Selected specimen with central edge notch were then tested in three-point bending and fragments after these tests were tested in compression. In the second part, attention was paid to the evaluation of fracture tests conducted on specimen from drill-cores taken from selected objects located at the former Transgas Gas Control Center in Prague. The specimen were provided with a chevron notch before being tested in three-point bending. The measured data was modified by the GTDiPS program and in the case of the glass composite the StiCrack program was used to evaluate fracture parameters.
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Advanced evaluation of fracture tests of selected rock specimens
Kubeš, Pavel ; Veselý, Václav (referee) ; Keršner, Zbyněk (advisor)
This bachelor's thesis deals with the advanced evaluation of fracture tests of selected rock (sandstone) specimens. The first part describes several fracture models/methods, fracture-mechanical parameters, process and configuration of the tests, used specimens and the procedure of data processing using the program GTDiPS. The second part contains neatly sorted evaluation of load-displacement diagrams. The results of the work are calculated fracture-mechanical parameters of various sandstones and their mutual comparison.
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Advanced evaluation of selected fracture tests of fibre reinforcement concrete specimens
Majda, Tomáš ; Frantík, Petr (referee) ; Keršner, Zbyněk (advisor)
The goal of this thesis was evaluation of extensive series of selected three point bending tests on fibre reinforced concrete specimens of ages 7, 28 and 126 days. First the measured data were adjusted by GTDiPS software. Than the assumed contribution of fibres in load--deflection diagram was approximated by regressive function. Contribution of matrix was calculated by deducting the approximated part from full diagram. Using StiCrack software the Young modulus, fracture toughness and fracture energy were calculated for both original and approximated diagram. All results were evaluated and tabled.
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Porušování jemnozrnného cementového kompozitu v blízkosti rozhraní plniva a matrice
Vyhlídal, Michal ; Kabele,, Petr (referee) ; Profant, Tomáš (referee) ; Keršner, Zbyněk (advisor)
The Interfacial Transition Zone (ITZ) between the aggregate grain/reinforcement bar and the matrix is considered to be the weakest element in cementitious composites and is, according to some authors, directly responsible for the nonlinear (more precisely, quasi-brittle) behavior of the composites. The aim of this work is verification of the generally accepted paradigm of the weakest element by means of fracture experiments and corresponding numerical simulations. In the experimental part, in addition to traditional fracture tests, modern methods of 3D scanning, scanning electron microscopy, chemical analysis using an electron microprobe and nanoindentation were used. In the numerical part, models based on generalized linear elastic fracture mechanics as well as modern models intended for the simulation of cement composites, namely crack band model with smeared cracks and the Microplane model, were used. Based on the results, the numerical part was complemented by the Cohesive Zone Material model simulating the behavior of the interface. All results are discussed and put into context with already published work. The main conclusion of the work is that the properties of the ITZ do not have such an influence on the behavior of cement composites as the adhesion between the inclusion and the ITZ, i.e. the matrix.
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Fracture tests of selected specimens with special aggregates: experiments and numerical simulation
Majda, Tomáš ; Malíková, Lucie (referee) ; Keršner, Zbyněk (advisor)
The diploma thesis deals with selected fracture tests and evaluation of fracture parameters of cement-based composite. One part of the thesis deals with cement-based composite with glass spherical aggregate of a single fraction of 2 mm. After production, the beams with dimensions of 20×40×200mm exposed to temperatures in the range from 100 to 1000 °C for one hour. Using the non-destructive ultrasonic pulse method, the degree of damage caused by termal load was determined. Selected specimen with central edge notch were then tested in three-point bending and fragments after these tests were tested in compression. In the second part, attention was paid to the evaluation of fracture tests conducted on specimen from drill-cores taken from selected objects located at the former Transgas Gas Control Center in Prague. The specimen were provided with a chevron notch before being tested in three-point bending. The measured data was modified by the GTDiPS program and in the case of the glass composite the StiCrack program was used to evaluate fracture parameters.
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Advanced evaluation of selected fracture tests of fibre reinforcement concrete specimens
Majda, Tomáš ; Frantík, Petr (referee) ; Keršner, Zbyněk (advisor)
The goal of this thesis was evaluation of extensive series of selected three point bending tests on fibre reinforced concrete specimens of ages 7, 28 and 126 days. First the measured data were adjusted by GTDiPS software. Than the assumed contribution of fibres in load--deflection diagram was approximated by regressive function. Contribution of matrix was calculated by deducting the approximated part from full diagram. Using StiCrack software the Young modulus, fracture toughness and fracture energy were calculated for both original and approximated diagram. All results were evaluated and tabled.
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Advanced evaluation of fracture tests of selected rock specimens
Kubeš, Pavel ; Veselý, Václav (referee) ; Keršner, Zbyněk (advisor)
This bachelor's thesis deals with the advanced evaluation of fracture tests of selected rock (sandstone) specimens. The first part describes several fracture models/methods, fracture-mechanical parameters, process and configuration of the tests, used specimens and the procedure of data processing using the program GTDiPS. The second part contains neatly sorted evaluation of load-displacement diagrams. The results of the work are calculated fracture-mechanical parameters of various sandstones and their mutual comparison.
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Initiation of stable crack propagation of selected building composites
Majtánová, Romana Viktória ; Veselý, Václav (referee) ; Keršner, Zbyněk (advisor)
The purpose of my bachelor’s thesis is study of the effects of fibres in normal-weight concrete and light-weight concrete. Specimens were prepared from concrete with polypropylene fibres FORTA FERRO of three different lengths – 19, 38 and 54 mm – and also reference concrete (without fibres) was prepared. This thesis contains gradual evaluation of fracture tests on specimens from mentioned materials. The used fracture test was a three–point bending fracture test on beams with a central notch. From the measured load–deflection in the middle of span and load–crack mouth opening displacement diagrams were determined values of modulus of elasticity, unstable fracture toughness, initiation part of fracture toughness and also load level for beginning of stable crack propagation composites. For determination was used „double–K“ fracture model. For illustration is described evaluation using the effective crack model.
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