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Parameters of Fracture Mechanics
Oplt, Tomáš ; Ševeček, Oldřich (referee) ; Horníková, Jana (advisor)
This thesis is the descriptive summary for the most significant parameters of fracture mechanics, required to define stress field on the crack tip. The first and also the most extensive part is divided into two subparts. There are mentioned particular parameters of one-parameter fracture mechanics, firstly are considered linear elastic deformations, thereafter the elastoplastic deformations. The second, shorter part of the thesis, is aimed at multi-parameters stress field description on the crack tip, required for the calculation of constructions with the necessity to consider their geometry.
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Problems of the complex potentials of the isotropic elasticity
Kubíček, Radek ; Hrstka, Miroslav (referee) ; Profant, Tomáš (advisor)
The presented diploma thesis concerns linear fracture mechanics and deals with determination of the stress intensity factor of the finite crack, which is located in the vicinity of the bimaterial interface, solved by the distributed dislocation technique and theory of complex potencials. The work is possible to devide into three parts. The first part includes basic concepts of the linear fracture mechanics and is also dedicated to the mechanics of composite materials. The second part deals with the determination of the stress intensity factor from solving singular integral equation formulated by Bueckner's principle and the distributed dislocation technique. The third part includes the specific configuration of the crack with respect to the bimaterial interface and the solution, which is compared with results obtained from the FE analysis.
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Analysis of the causes of cracks on the wheeel rims
Plundrák, David ; Němec, Karel (referee) ; Foret, Rudolf (advisor)
This thesis looks for the causes of cracks in bicycle rims in the most stressed areas (in places holes for wires). For this reason, in this work is the stress and strain analysis of a simple model of the rim to the working load is given and further the complete production process of the rim is described. As an experimental material were used rims from different producers of aluminum alloy EN AW 6061 and EN AW 6082 T6 temper, in which a crack started to spread. For assessment of rims materials the methods of optical spectroscopy, optical microscopy, scanning electron microscopy, Vickers hardness test were used and for finding another crack penetration test was performed. Based on the performed experiments bad design solution of rivets was found in the rim 1. Broken rivets initiated fatigue cracks. Material of rim 1 was alright. The other two rims were deficiencies in materials. For the rim 2 was a problem with coarse-grained recrystallized structure. The insufficiently rapid cooling for the rim 3 caused exclusion hardening phase (particularly copper phase) at grain boundaries. Moreover, the rim 3 is not cured to the required parameters. Aluminium alloys are an ideal material for bicycle rims. However, they require reliable design solutions and meeting the physical metallurgy, which lies in the knowledge and use of influences of chemical composition, forming and heat treatment on mechanical, chemical, physical and technological properties.
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Brick Building Reconstruction
Kolářová, Jana ; Bažant,, Zdeněk (referee) ; Šulák, Pavel (advisor)
This bachelor’s thesis is focused on reconstruction of brick apartment houses in terms of static load capacity. The thesis summarizes the requirements and information to evaluate the current state of brick buildings, contains both theoretical and practical calculations to assess the load capacity of masonry elements, and suggests possible measures for structures in unsatisfactory conditions.
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Design of the uderground part of the building
Šimek, Ondřej ; Hrubý, Tomáš (referee) ; Klusáček, Ladislav (advisor)
The bachelor‘s thesis deals with the design and assessment of reinforced concrete monolithic supporting structure of underground garages under apartment building at ultimate limit state and also at serviceability limit state, according to ČSN EN 1992-1-1: Design of concrete structures. Specifically, the design of the ceiling slab, girders, the selected column, the selected part of the wall and foundation under columns. Other parts of the building are not solved in the project. The text part contains general information on the desing of the structure, static idealization of the structure, type of load and method for calculation of inner forces. Attachments contain structural analysis, which completes the text part and solves in detail selected elements of the structure and the drawing documentation.
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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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Design of underground garage under the block of flats
Císařová, Kateřina ; Hrubý, Tomáš (referee) ; Klusáček, Ladislav (advisor)
As the main topic this thesis describes the design and evaluation of selected reinforced concrete members of the underground garage construction of the administration building at ultimate limit state and also at serviceability limit state, both in accordance with EC2: Design of Concrete Structures. Designed members in particular are monolithic slab, girders and columns. Structural design and evaluation of other structures of the building are not part of this thesis. The text part of the thesis concerns the descriptions of analysed structures and also the descriptions of the loads acting on them. Method of designing of the structures, methods of calculating of inner forces, and also the method of modelling the structure in software SCIA Engineer are herein further described. The annexes are mainly structural analysis, which expresses the knowledge obtained from the theoretical part of this thesis, and the drawing documentation.
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Software for an estimation of residual fatigue lifetime of mechanical parts with crack
Motyka, Jakub ; Náhlík, Luboš (referee) ; Pokorný, Pavel (advisor)
This bachelor thesis deals with the creation of software for determining the residual fatigue time of mechanical parts with a crack. In the calculation of the lifetime of fatigue-stressed parts, the existence of an initial crack is assumed. During the operating load of the part, the crack may grow up to a critical size, when a sudden fracture of the part occurs. Knowledge of the number of residual loading cycles is important for machine design and safe part-operation. The first part of this thesis deals with linear-elastic fracture mechanics which forms the theoretical basis of the calculation software. The second part is devoted to the software itself, its principles and work in user interface. The last part compares the software-acquired results with the results reached analytically.
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Possibilities of estimation of selected fracture parameters under conditions of LEFM
Zouhar, Petr ; Hutař, Pavel (referee) ; Ševčík, Martin (advisor)
The presented bachelor´s thesis deals with possibilities of estimation of selected fracture parameters under conditions of linear elastic fracture mechanic (LEFM). The aim of this thesis is to quantify the accuracy of specific methods for the estimation of fracture parameters from a known stress and strain field obtained using numerical methods. 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 LEFM and selected methods used for estimation of fracture parameters, namely the stress intensity factor, strain energy release rate and J-integral. A detailed description of the numerical model, a sensitivity analysis of the FEM mesh density and obtained results are described in the second part, focused on the solution of the problem,. The accuracy of each method is expressed by comparing with a known reference value of stress intensity factor. The applicability of selected methods for estimation of the stress intensity factor is shown on a practical example of three-dimensional body containing a crack.
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