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Description of creep crack propagation in electrofusion sockets for polymer pipes connection
Helešicová, Petra ; Horníková, Jana (referee) ; Trávníček, Lukáš (advisor)
The presented bachelor’s thesis deals with crack propagation by the slow crack growth mechanism in electrofusion sockets used for welding of polymer pipes. The thesis can be divided into several parts. First part presents a research on the topic of polymer pipes, materials used for their production, types of failures and ways of connecting including detailed description of the process of electrofusion welding with electrofusion sockets. Next part is focused on fracture mechanics that is used for the practical part of the thesis. The theory of linear elastic fracture mechanics and its stress-intensity approach are described. Different ways of obtaining the stress intensity factor, which is the main parameter used to describe the stress distribution at the crack tip, are presented. The practical part of the thesis focuses on numerical modelling of crack propagation through an electrofusion socket wall and calculating values of stress intensity factor in dependence on the crack length. The creation of the numerical model for the crack propagation simulation is described. The direction of propagation is evaluated using MTS criterion. The whole simulation is carried out by a parametric macro created using the APDL language. The main goal of the thesis is to describe the influence of the socket geometry or joint configuration changes on the stress intensity factor values and calculated lifetimes. The stress intensity factor functions for the modified configurations are compared to the original. At the end of the thesis, lifetime estimations of the electrofusion sockets are also calculated using the stress intensity factor functions and compared.
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Expected Fatigue Crack Propagation with Selected Geometric Shapes in IPE 80
Juhászová, Tereza ; Seitl, Stanislav ; Miarka, Petr
The focus of this contribution is to investigate fatigue behaviour of I cross-section beam. Stainless steel IPE beam with initiate concentrator is loaded in three point bending and the crack growth rate is analysed for various crack front shapes. Stress intensity factor size in the crack tip is being investigated in relation to growth rate of discontinuity. Load number of cycles is predictable basing on hypothesis of fatigue behaviour of material and the results are compared to experimental results of studies performed on compact tension specimen made from the similar material.
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Description of creep crack propagation in electrofusion sockets for polymer pipes connection
Helešicová, Petra ; Horníková, Jana (referee) ; Trávníček, Lukáš (advisor)
The presented bachelor’s thesis deals with crack propagation by the slow crack growth mechanism in electrofusion sockets used for welding of polymer pipes. The thesis can be divided into several parts. First part presents a research on the topic of polymer pipes, materials used for their production, types of failures and ways of connecting including detailed description of the process of electrofusion welding with electrofusion sockets. Next part is focused on fracture mechanics that is used for the practical part of the thesis. The theory of linear elastic fracture mechanics and its stress-intensity approach are described. Different ways of obtaining the stress intensity factor, which is the main parameter used to describe the stress distribution at the crack tip, are presented. The practical part of the thesis focuses on numerical modelling of crack propagation through an electrofusion socket wall and calculating values of stress intensity factor in dependence on the crack length. The creation of the numerical model for the crack propagation simulation is described. The direction of propagation is evaluated using MTS criterion. The whole simulation is carried out by a parametric macro created using the APDL language. The main goal of the thesis is to describe the influence of the socket geometry or joint configuration changes on the stress intensity factor values and calculated lifetimes. The stress intensity factor functions for the modified configurations are compared to the original. At the end of the thesis, lifetime estimations of the electrofusion sockets are also calculated using the stress intensity factor functions and compared.
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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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Description of Stress and Strain States at Front of Inclined Cracks Loaded by Shear Modes
Roh, Marek ; Majer, Zdeněk (referee) ; Horníková, Jana (advisor)
The primary objective of this masters thesis is to assess the eects of the length of crack and the angle, of which is this crack inclined on the stress and strain states at its front for the test sample loaded under shear. The rst part of this thesis will analyze the individual approaches that lead to the description of the aforementioned conditions. The second part deals with the FEM model assembly, which will lead to the fracture parameters, the values of which will be compared in part three.
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Influence of Friction to the Shear Stress State in the Crack-Front Vicinity
Vlach, Jiří ; Hutař, Pavel (referee) ; Horníková, Jana (advisor)
The aim of this master thesis is to explore the influence of frictional forces to the stress and strain on the straight crack tip loaded in shear modes. The first section summarizes the most important things from the field of fracture mechanics. Especially theoretical knowledge about fracture parameters (stress intensity factor, J – integral) and their determination in computational environment ANSYS Workbench. The second part deals with computational modeling. At the beginning, is created the model of material, the model of geometry, the model of loads, etc. Then it is possible to solve the direct problem outlined in the introduction. A result of this thesis is the assessment of how the friction influences the fracture parameters in shear modes II and III.
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Procedure of residual fatigue lifetime assesment of railway axle
Scholz, David ; Seitl, Stanislav (referee) ; Náhlík, Luboš (advisor)
The goal of the bachelor's thesis is to present options to calculate residual life of a railway axle from more sophisticated points of view. These methods are requested by railway operators to ensure higher safety of train traffic. The main issue is the perspective of fracture mechanic, considering railway axle as a component with an initial crack or other defect. The theoretical part deals with basic definitions of fracture mechanics and processes describing crack propagation, using conception of stress intensity factor, which is the most used nowadays. Following part also describes a fatique life estimation process in real. This process is demon-strated using an example after that.
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Residual fatigue lifetime of model railway axle
Netopil, Vladimír ; Majer, Zdeněk (referee) ; Náhlík, Luboš (advisor)
The aim of this diploma thesis is to estimate the residual fatigue lifetime of the model train axle. Primarily, the thesis is focused on determination of the stress intesity factor, the main variable for estimation of the residual fatigue lifetime. At first, the theoretical approaches of estimation of the residual fatigue lifetime are listed and then the residual fatigue lifetime of the model train axle is estimated.
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An aplication of the mathematical dislocation theory to the problem of the crack in the vicinity of the bi-material interface
Padělek, Petr ; Hrstka, Miroslav (referee) ; Profant, Tomáš (advisor)
The presented diploma thesis deals with a problem of the determination of the stress intensity factor of the finite length crack in the vicinity of the bi-material interface solved by the distributed dislocation technique. The work is divided into several parts. The first part is theoretical and includes basic concepts of the fracture mechanics, the crack behaviour at the bi-material interface, the formulation of the singular integral equation by virtue of the distributed dislocation technique, the Bueckner's principle, complex potentials and consequently the determination of the stress intensity factor. The second part is the theory application to the specific configuration of the crack of the finite length with respect to the bi-material interface and in the third part, there is carried out the solution of this problem for various configurations of the bi-material solved by the distributed dislocation technique and its comparison with the results obtained from the FE analysis.
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Residual fatigue life estimation of railway wheelset
Pokorný, Pavel ; Zouhar, Michal (referee) ; Náhlík, Luboš (advisor)
The first part of this master's thesis deals with the high cycle fatigue of materials, especially on growing cracks using linear elastic fracture mechanics. Much of this work is focused on the concept of stress intensity factor. This concept is nowadays one of the most widely used concepts for describing a body with crack. The first part ends with theoretical approaches to determine the residual fatigue life of the body with a crack. The second part of this master's thesis is focused on the determination of residual fatigue life of a specified railway wheelset. An existence of crack-like defect is assumed at the railway wheelset. The goal of this master's thesis is to estimate how long it will take to grow from initial defect to a critical crack length. The last part of this master's thesis is devoted to addiction order load cycles on crack growth rate.
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