|
|
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.
|
|
|
Analysis of composite sandwich panel under conditions simulating placement on a rocket carrier
Král, Martin ; Horníková, Jana (referee) ; Majer, Zdeněk (advisor)
This work deals with composite sandwich panels, which are currently used as supporting structures for satellites. This type of panel contains an aluminum honeycomb core and two thin laminate coatings, reinforced with carbon fibers. Laminate sandwich panel coatings offer an alternative to conventional aluminum coatings, which is advantageous mainly due to the reduction of weight and increase of the flexural stiffness of the panels. The work is a parametric study of mechanical properties for several variants of the coating of sandwich panels. These are laminate coatings, differing in the orientation of the fibers in the individual layers, as well as an aluminum alloy coating. The study is divided into two parts. The first part examines the deformation-stress response of a sandwich panel, which is simply supported at the edges and loaded with pressure. The response calculation is performed using FEM and verified by the method of sum of an infinite series. The second part investigates the deformation-stress response of the joint, (node) of two sandwich panels, which is loaded by random vibrations, aimed at simulating the mechanical environment of the rocket carrier during the takeoff of the launch vehicle. The response is calculated using FEM and verified by an experiment on a vibrating stool for a selected variant of the laminate coating of sandwich panels. The results of the work can be used for the design of baffle of the X-ray imaging device (SXI), which is part of the equipment of the space satellite of the SMILE project.
|
|
|
Models of plastic zone on the crack front
Surovec, Jindřich ; Žák, Stanislav (referee) ; Horníková, Jana (advisor)
This bachelor thesis is about analytical determination of plastic zone shape at the crack tip using Von Mises and max yield criterions. Next goal is obtain characterictic parameters of kinked crack. Theoretical part clarifies some basic concepts needed to understand the analytical models, then follows the analytical solution itself.
|
|
|
Assessment of surface roughness and its influence on fatigue life
Dziubek, Jan ; Chamrad, Jakub (referee) ; Horníková, Jana (advisor)
This thesis deals with influence of surface roughness on fatigue life. In the thesis, the evaluation of the surface roughness by the profile method according to the standard ČSN EN ISO 4287 is specified. Within the work, the roughness parameters of samples with different surface treatment were determined. Then, SN-curves were drawn for samples with different surface treatments and compared with each other.
|
|
|
Relationship of force and deformation characteristics to the energy of deformed system
Kupka, Oldřich ; Konvalinka, Jan (referee) ; Horníková, Jana (advisor)
The bachelor´s thesis deals with the description of energy in deformed systems and their use to determine the force acting on the system and displacements caused by forces. In the first part of the thesis there are described the basic types of stresses and how it is possible to determine their strain energy and displacements. After that, strain and potential energy including their complementary components are described. Next part is explanation of the principle of virtual work, Betti's theorem and Maxwell's reciprocity theorem. In the second part of thesis, the first and the second Castigliano´s theorems are derived. Castigliano´s theorems are applied to a statically determinate and indeterminate problems.
|
|
|
Deformation and stress fields at the front of shear cracks with complicated geometry
Žák, Stanislav ; Hutař,, Pavel (referee) ; Kunz,, Jiří (referee) ; Horníková, Jana (advisor)
Tato závěrečná práce je shrnutím výzkumu smykově zatěžovaných trhlin, který proběhl v průběhu čtyř let doktorského studia jejich autora Ing. Stanislava Žáka (Středoevropský technologický institut, Vysoké učení technické v Brně). Předložená práce je zaměřena na prohloubení znalostí v oblasti pokročilé lomové mechaniky, konkrétně pro smykové zatěžování trhlin kombinované s případy geometrických odchylek trhlin od běžně používaných modelů. To mimo jiné znamená návrh nových přístupů a modelů a popis součinitelů intenzity napětí pro geometricky komplikované trhliny. První část práce je věnována shrnutí současných přístupů v lomové mechanice a dále i popisu numerických metod, použitých v dalších výpočtech. Kromě klasických přístupů se tato část textu zabývá i novějším výzkumem zaměřeným na smykové zatěžování trhlin, speciálně pro dva typy zkušebních těles – válcový vzorek s obvodovým vrubem a trhlinou zatížený prostým smykem nebo krutem a CTS těleso umožňující zatížení trhliny v módech I, II a také v jejich kombinaci I+II. Další část textu je zaměřena na konkrétní výpočty lomových parametrů při použití nových modelů s komplikovaným čelem trhliny. Teoretické řešení lomových parametrů pro oba výše zmíněné modely je porovnáno s experimentálními výsledky, získanými v navazujících projektech. U modelu válcového vzorku je popsána možnost zjednodušení budoucích modelů těles s podobným typem komplikované trhliny a současně je na něm popsán lokální vliv zubatosti čela trhliny na indukci lokálního zatížení v módu II při globálním zatížení v módu III. Tyto výsledky jsou přímo propojeny s experimentální kvantifikací únavového šíření lomu při zatížení v módu III. CTS těleso je použito k popisu vlivu drsnosti trhliny na součinitele intenzity napětí. Na tomto modelu je pozorován jak globální pokles hodnoty KII při zvyšující se drsnosti trhliny, tak i lokální změny v namáhání trhliny podél jednotlivých nerovností. Výsledky potvrzují, i pro dosud málo zkoumané smykové zatěžování, že mikrostruktura lomových ploch a čela trhliny má vliv na lomové parametry. Rozšiřují tak současné znalosti v oboru lomové mechaniky popisem geometrického stínění čela trhliny pro zátěžné módy II a III.
|
|
|
Influence of a Notch on Stress-Strain States at the Front of Cracks Loaded by Shear Modes
Ščotka, Martin ; Žák, Stanislav (referee) ; Horníková, Jana (advisor)
This diploma thesis deals with influence of a notch on stress-strain states at the front of cracks by shear modes. Starting with fracture mechanics and its division, followed by stress intensity factor and calculate its by finite element method. Calculation is solved for two types of notches, U-notched and V-notched, both notches were modeled parametrically so their geometry was changeable and stress intensity factor were calculated for all configurations. Subsequently was solved next calculation of stress intensity factor but for shaft without notch. Finally, was evaluated influence of notch on stress intensity factor. Software for finite element method has been used ANSYS. Others calculation was provided in software MATLAB
|
|
|
Numerical simulation of crack propagation in ceramic composites in 3D
Svoboda, Josef ; Horníková, Jana (referee) ; Majer, Zdeněk (advisor)
The strength of materials such as glass and ceramics can be influenced by the environment (stress corrosion). Under applied stress defects (cracks) can grow sub-critically below fracture toughness K_Ic. The aim of this work was to develop a three-dimensional finite-element model to analyze the subcritical crack growth behavior of ceramic-based particulate composites. The maximum tangential stress criterion (MTS) was used to predict the direction of the crack propagation in the framework of linear elastic fracture mechanics. The modeled material was a Low Temperature Co-fired Ceramics (LTCC), containing alumina particles embedded in a glass matrix. The main aim of this work was to develop a 3D model describing the crack growth. Conclusions from this work can contribute to a better understanding of subcritical crack propagation in particle composites.
|
|
|
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.
|
|
|
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.
|
guest ::
RSS feed.