|
|
Basic features of aggregate-matrix-interface fracture of selected building composites
Vyhlídal, Michal ; Seitl, Stanislav (referee) ; Keršner, Zbyněk (advisor)
The aim of this work is to analyze the behavior of cement composite, depending on the features of ITZ. The first part of the thesis is theoretical and deals with the origin and features of ITZ, defines the basic relationships and concepts of continuum mechanics and linear elastic fracture mechanics and presents crack tips posibilities in the three-phase composite, including their short characterization. The second part is practical and describes creation of numerical model in the ANSYS software, presentation of partial results and compare of them. The result of this work is a comparison of the mean values of stress and amplitude of stress depending on the features of ITZ.
|
|
|
Fracture of selected building composites in the vicinity of aggregate-matrix-interface
Vyhlídal, Michal ; Malíková, Lucie (referee) ; Keršner, Zbyněk (advisor)
The interface between aggregate grains and matrix in cementitious composites is their weakest element. The topic is particularly significant in the case of high performance and high strength concrete technology for which the eliminination or reduction of these weak links are necessary. The aim of this thesis is to determine the influence of the interface on the fracture behaviour of the cementitious composites. The fracture experiments were performed for this purpose and were complemented by the nanoindentation’s results and scanning electron microscopy results. Numerical model was created in ANSYS software on the basis of these data and the fracture toughness values of the interface were evaluated by means of the generalized fracture mechanics principles. Conclusion of the thesis is proof that the interface properties have a significant influence on the fracture behaviour of cementitious composites.
|
|
|
Strategy Competitive Fight
Vyhlídal, Martin ; MBA, Stanislav Heža, (referee) ; Bartes, František (advisor)
The thesis deals with finding such a competitive strategy, which enables a well-established Copany to remain on the leading edge of sales finance market in the Czech Republic. To do that, it is necessary to acquire as detailed information about competitors´ activities, professional environment development and end-user preferences trend, as possible. Based on this information it proposes possible models of strategic options including the impact on customers, business partners and internal issues.
|
|
|
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.
|
|
|
Influence of Non-Local Parameters of Microplane Model on the Simulated Response of the Beam
Vyhlídal, Michal
In this work, the influence of non-local parameters of microplane model for the case of specimens with nominal dimensions 40×40×160 mm with central edge notch with a depth of 12 mm and thickness of 1 mm, which are tested in three-point bending configuration, is analysed. The aim of this work is analysis of the influence of these parameters on the simulated behaviour of cement composite despite the fact that their experimental determination is basically impossible. The results of detailed numerical analysis show that the influence of non-local parameters is not negligible. In general, one can say that the higher their value is, the higher the simulated load bearing capacity of the specimens is achieved.
|
|
|
Possibilities of using 4D computed tomography in fracture tests
Kumpová, Ivana ; Fíla, Tomáš ; Koudelka, Petr ; Rozsypalová, I. ; Keršner, Z. ; Kytýř, Daniel ; Vopálenský, Michal ; Vavřík, Daniel ; Vyhlídal, M. ; Drdácký, Miloš
The paper presents the study of the internal structure and fracture properties of selected quasi-brittle building materials subjected to temperature changes and the possibility of applying the method combining bending fracture tests and time-dependent computed tomography (4D CT). The tested specimens were subjected to hightemperature effects and subsequently tested by a four-point bending during 4D CT. Thus, 3D image information was obtained in different phases of loading and material damage. Comparative compression strength measurements were also performed. These results are in good agreement
|
|
|
Basic features of aggregate-matrix-interface fracture of concrete: pilot modelling
Vyhlídal, M. ; Šimonová, H. ; Veselý, V. ; Keršner, Z. ; Klusák, Jan ; Malíková, Lucie
In this paper, the attention is paid to investigation of the importance of the Interfacial Transition Zone (ITZ) in concrete for the global fracture behaviour. A simplified cracked geometry (consisting matrix, ITZ and aggregate) is modelled by means of the finite element method with a crack terminating at the matrix-ITZ interface. Numerical studies assuming two various ITZ thicknesses and several various ITZ elastic moduli are performed. Based on the values of the opening stress ahead of the crack tip (its average value and stress range) a few conclusions are discussed. The pilot analyses dealing with the effect of ITZ on the stress distribution should contribute to better description of toughening mechanisms in silicate-based composites.
|
|
|
Fracture of selected building composites in the vicinity of aggregate-matrix-interface
Vyhlídal, Michal ; Malíková, Lucie (referee) ; Keršner, Zbyněk (advisor)
The interface between aggregate grains and matrix in cementitious composites is their weakest element. The topic is particularly significant in the case of high performance and high strength concrete technology for which the eliminination or reduction of these weak links are necessary. The aim of this thesis is to determine the influence of the interface on the fracture behaviour of the cementitious composites. The fracture experiments were performed for this purpose and were complemented by the nanoindentation’s results and scanning electron microscopy results. Numerical model was created in ANSYS software on the basis of these data and the fracture toughness values of the interface were evaluated by means of the generalized fracture mechanics principles. Conclusion of the thesis is proof that the interface properties have a significant influence on the fracture behaviour of cementitious composites.
|
|
|
Basic features of aggregate-matrix-interface fracture of selected building composites
Vyhlídal, Michal ; Seitl, Stanislav (referee) ; Keršner, Zbyněk (advisor)
The aim of this work is to analyze the behavior of cement composite, depending on the features of ITZ. The first part of the thesis is theoretical and deals with the origin and features of ITZ, defines the basic relationships and concepts of continuum mechanics and linear elastic fracture mechanics and presents crack tips posibilities in the three-phase composite, including their short characterization. The second part is practical and describes creation of numerical model in the ANSYS software, presentation of partial results and compare of them. The result of this work is a comparison of the mean values of stress and amplitude of stress depending on the features of ITZ.
|
|
|
Strategy Competitive Fight
Vyhlídal, Martin ; MBA, Stanislav Heža, (referee) ; Bartes, František (advisor)
The thesis deals with finding such a competitive strategy, which enables a well-established Copany to remain on the leading edge of sales finance market in the Czech Republic. To do that, it is necessary to acquire as detailed information about competitors´ activities, professional environment development and end-user preferences trend, as possible. Based on this information it proposes possible models of strategic options including the impact on customers, business partners and internal issues.
|
guest ::
RSS feed.