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Numerical support for description of behavior of cement based composite during fatigue test
Holušová, Táňa ; Padevět,, Pavel (referee) ; PhD, Ladislav Řoutil, (referee) ; Seitl, Stanislav (advisor)
The presented dissertation thesis is focused on analysis of alternative test method for determination of mechanical parameters of cement based composites. A disk shaped specimen with diameter 150 mm, thickness 60 mm was analysed and its modification for use on compact tension test (CT). Such a test is hereinafter referred to as modified compact tension (shortly MCT or MDCT)). This test configuration was chosen for testing the static and fatigue properties of cement based composites precisely because of its traditional use for fatigue testing of metallic materials. Specimens with a different cross-sections can also be used for MCT, but the work is exclusively focused on circular specimen, for example because it could be easily cut from drill core taken directly from the existing structure, on which the properties are more relevant to the age of the used concrete of the controlled structure. The modified compact tension test was firstly calibrated by numerical simulations involved the tuning of the shape of the numerical model and used material models of concrete and steel. Then the laboratory testing of modified compact tension on several levels were performed. The adequacy of the numerical model was verified against the pilot laboratory testing of the MCT test. Furthermore, the comparison of the modified compact tension test and its suitability for determining of fracture mechanical parameters of cement based composites with the three point bending test, which is the standardized test configuration for these purposes was performed. Another laboratory testing was focused of determining of fracture mechanical parameters of concrete mixture classified in strength class C30/37 and the pilot study of fatigue parameters of the same strength class of the concrete mix. The work was also presented numerical simulations of the push-out test, focused on the connection of concrete and steel with epoxy adhesive.
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Bend specimens: Numerical support in software ANSYS
Viszlay, Viliam ; Šimonová, Hana (referee) ; Seitl, Stanislav (advisor)
The aim of the thesis is the investigation of fracture-mechanics parameters on specimens made of quasi-brittle materials. The principles of two-parameter fracture mechanics are used. Couple of numerical simulations were done and their outputs are used for two main analysed specimen geometries. For simulations the finite element method software ANSYS is used. In the first part, the thesis focuses on bended specimens. The influence of different geometric parameters on fracture mechanics behaviour of cracked specimen is investigated. For model calibration the outputs of other authors are used. In the second part the specimens for modified compact-tension test (CT test) are analysed. Similar to the first part, the influence of geometric parameters of the specimen (in this case, the specimen size) on fracture mechanics parameters were investigated. The modified CT test was derived from CT test which is commonly used for metal materials testing as the suitable geometry for cement-based composite materials testing. The outputs of both parts are calibration polynomials, which are expressions obtained for different specimen geometries, giving the value of fracture mechanics parameter as the function of specimen geometry. As the example, calibration curves are used to obtain fracture toughness of tested material using the outputs from recent experiment.
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Numerical support for analysis of the fatigue behavior of cement based composites
Viszlay, Viliam ; Keršner, Zbyněk (referee) ; Seitl, Stanislav (advisor)
This thesis is focused on numerical analysis of fracture mechanics parameters in modified compact tension (CT) test. This CT test appears to be a suitable alternative to classic compact tension test for using for testing of quasi-brittle materials. The classic compact tension test is commonly used for fatigue testing of metallic materials and the geometry of used specimens does not allow using this test for quasi-brittle materials like cement based composites. The modified version of this test with cylindrical shape of the specimen allows us to test fatigue behaviour of quasi-brittle materials. In this thesis the influence of the modification of classic CT test on fracture mechanic parameters are determinated. In the next step, the influence of the position of steel bars (the position of loading force) on fracture mechanic parameters are evaluated. Obtained values are presented in graphs and calibration polynomials for each geometry are proposed.
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Numerical support for description of behavior of cement based composite during fatigue test
Holušová, Táňa ; Padevět,, Pavel (referee) ; PhD, Ladislav Řoutil, (referee) ; Seitl, Stanislav (advisor)
The presented dissertation thesis is focused on analysis of alternative test method for determination of mechanical parameters of cement based composites. A disk shaped specimen with diameter 150 mm, thickness 60 mm was analysed and its modification for use on compact tension test (CT). Such a test is hereinafter referred to as modified compact tension (shortly MCT or MDCT)). This test configuration was chosen for testing the static and fatigue properties of cement based composites precisely because of its traditional use for fatigue testing of metallic materials. Specimens with a different cross-sections can also be used for MCT, but the work is exclusively focused on circular specimen, for example because it could be easily cut from drill core taken directly from the existing structure, on which the properties are more relevant to the age of the used concrete of the controlled structure. The modified compact tension test was firstly calibrated by numerical simulations involved the tuning of the shape of the numerical model and used material models of concrete and steel. Then the laboratory testing of modified compact tension on several levels were performed. The adequacy of the numerical model was verified against the pilot laboratory testing of the MCT test. Furthermore, the comparison of the modified compact tension test and its suitability for determining of fracture mechanical parameters of cement based composites with the three point bending test, which is the standardized test configuration for these purposes was performed. Another laboratory testing was focused of determining of fracture mechanical parameters of concrete mixture classified in strength class C30/37 and the pilot study of fatigue parameters of the same strength class of the concrete mix. The work was also presented numerical simulations of the push-out test, focused on the connection of concrete and steel with epoxy adhesive.
|
|
|
Bend specimens: Numerical support in software ANSYS
Viszlay, Viliam ; Šimonová, Hana (referee) ; Seitl, Stanislav (advisor)
The aim of the thesis is the investigation of fracture-mechanics parameters on specimens made of quasi-brittle materials. The principles of two-parameter fracture mechanics are used. Couple of numerical simulations were done and their outputs are used for two main analysed specimen geometries. For simulations the finite element method software ANSYS is used. In the first part, the thesis focuses on bended specimens. The influence of different geometric parameters on fracture mechanics behaviour of cracked specimen is investigated. For model calibration the outputs of other authors are used. In the second part the specimens for modified compact-tension test (CT test) are analysed. Similar to the first part, the influence of geometric parameters of the specimen (in this case, the specimen size) on fracture mechanics parameters were investigated. The modified CT test was derived from CT test which is commonly used for metal materials testing as the suitable geometry for cement-based composite materials testing. The outputs of both parts are calibration polynomials, which are expressions obtained for different specimen geometries, giving the value of fracture mechanics parameter as the function of specimen geometry. As the example, calibration curves are used to obtain fracture toughness of tested material using the outputs from recent experiment.
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Numerical support for analysis of the fatigue behavior of cement based composites
Viszlay, Viliam ; Keršner, Zbyněk (referee) ; Seitl, Stanislav (advisor)
This thesis is focused on numerical analysis of fracture mechanics parameters in modified compact tension (CT) test. This CT test appears to be a suitable alternative to classic compact tension test for using for testing of quasi-brittle materials. The classic compact tension test is commonly used for fatigue testing of metallic materials and the geometry of used specimens does not allow using this test for quasi-brittle materials like cement based composites. The modified version of this test with cylindrical shape of the specimen allows us to test fatigue behaviour of quasi-brittle materials. In this thesis the influence of the modification of classic CT test on fracture mechanic parameters are determinated. In the next step, the influence of the position of steel bars (the position of loading force) on fracture mechanic parameters are evaluated. Obtained values are presented in graphs and calibration polynomials for each geometry are proposed.
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Modified compact tension test: The influence of the steel bars position
Holušová, Táňa ; Seitl, Stanislav ; Fernández-Canteli, A.
Testing and analysis of fatigue behavior of homogeneous materials, such as concrete or other cement based composites, are one major problem being studied in this scientific field. In this contribution, adaptation of the compact tension test, well known its use in the testing of metallic materials, is pursued for crack propagation rate measurement on cement based composites using cylindrical specimens. In particular, the influence of the steel bars position on the fracture parameters is studied in the modified compact tension test. The numerical study is performed by ATENA 2D. The results are compared by Load-COD diagrams and the variation of the fracture parameters values is discussed.
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