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Application of generalized linear elastic fracture mechanics on estimation of crack propagation origin from sharp V-notch
Štegnerová, Kateřina ; Máša, Bohuslav (referee) ; Náhlík, Luboš (advisor)
The master thesis is focused on estimation of crack propagation origin from sharp V-notch. Stress distribution around the tip of the V-notch is described on the base of generalized linear elastic fracture mechanics. The change of the stress singularity exponent caused by geometry of the V-notch and the vertex singularity is taken into account. The first part of the work is devoted to the estimation of the stress singularity exponent of the V-notch either from stress distribution around the tip of the V-notch or by using analytical solution. Formerly derived stability criteria are applied in the second part of the work. The origin of the crack propagation is estimated for several experimental specimens. The aim of this thesis is to compare the available experimentally observed data with results obtained using those criteria based on the application of generalized linear elastic fracture mechanics developer at the Institute of Physics of Materials Academy of Sciences of the Czech Republic. The finite element code Ansys and mathematical software Matlab were used for the necessary calculations.
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Fatigue crack front shape estimation
Zouhar, Petr ; Klusák, Jan (referee) ; Hutař, Pavel (advisor)
The presented master’s thesis deals with fatigue crack front shape estimation. The aim of this thesis is to create an iterative process leading to the real fatigue crack front shape. 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 linear elastic fracture mechanic (LEFM), methods used for estimation of stress intensity factor and stress singularity exponent. The first part further describes some phenomenon’s accompanying the mechanism of fatigue crack growth as for example crack tip curving and crack closure. In the second part of the thesis there is studied an affect of the free surface on the fracture parameters, especially the affected distance from the free surface is determined. Based on the assumption of a constant stress intensity factor and stress singularity exponent along the crack front, an iterative process leading to fatigue crack front shape is presented. The accuracy of the result is discussed by comparing of obtained crack front shapes with experimental data at the end of the thesis.
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Problems of the crack near the bimaterial interface
Svoboda, Miroslav ; Klusák, Jan (referee) ; Profant, Tomáš (advisor)
Subject of this work is resolving problems of linear crack mechanics, description of stress and deformations in the vicinity of the top of the concentrator with plane elasticity theory in orthotropy materials. First part is engaged in basic relations in crack mechanics. Second part is engaged in numeric-analytic algorithm for determination of stress singularity of crack perpendicular to interface of two materials. Third part is focused on testing algorithm on specific configuration of material and tension of crack in bimaterial interface. In the conclusion, numeric results and impact of mechanic qualities of materials with crack perpendicular to their interface are evaluated.
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A study of the stress distribution near the sharp notch tip
Svoboda, Petr ; Majer, Zdeněk (referee) ; Profant, Tomáš (advisor)
The presented diploma thesis deals with the problem of determining the stress singularity exponent of the V-notch. This task can be divided into two parts. The first deals with the theoretical background, that means the basic relations of mechanics and the basic concepts of fracture mechanics. The second part deals with the elaboration of the Williams method and the creation of a program for calculating the stress singularity exponent.
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A study of the stress distribution around the bimaterial notch tip
Hrstka, Miroslav ; Klusák, Jan (referee) ; Profant, Tomáš (advisor)
Presented bachelor’s thesis deals with determination of stress singularity exponent, by which is possible to completely define the stress distribution around the bimaterial notch tip. This task is divided in four parts. The first part concerns with basics of fracture mechanics, concretely linear elastic fracture mechanics of crack and Irwin’s conception of stress intensity factor. The second part deals with generalizing of linear fracture mechanics to notches. In the third part is initiated the numeric-analytical algorithm for computation of stress singularity exponent and determination of strains and stresses of given notch, which is compounded from two orthotropic materials. The last part is created by numerical example, in which the concrete configurations of notches are tested in calculating software.
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A study of the stress distribution around the bimaterial notch tip in the terms of the generalized stress intensity factor
Hrstka, Miroslav ; Kotoul, Michal (referee) ; Profant, Tomáš (advisor)
The presented diploma thesis deals with a problem of a generalized stress intensity factor determination and a consecutive study of stress distribution around the bimaterial notch tip, combining analytical and numerical methods. This task is possible to sectionalize into three parts. The first part is dedicated to the fundamentals of the linear fracture mechanics and the mechanics of composite materials. The second part deals with methods of anisotropic plane elasticity solution. Pursuant to the solution the computational models in the third part are created. The first model makes for determination of a singularity exponent eigenvalue by dint of Lekhnitskii-Eshelby-Stroh formalism. The second model makes for determination of the generalized stress intensity factor using psi-integral method, which is based on the Betti reciprocal theorem. All needed calculation are performed in the software ANSYS 12, Maple 12 and Silverforst FTN95. Results will be compared with the values obtained from a direct method of the generalised stress intensity factor determination.
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Problem of the crack terminating at the bimaterial interface
Svoboda, Miroslav ; Ševeček, Oldřich (referee) ; Profant, Tomáš (advisor)
The objective of this diploma thesis is the stress-strain analysis of the crack terminating at the orthotropic bi-material interface suggested as the plane problem of the linear fracture mechanics. The first part is engaged in basic relations of the linear fracture mechanics. The second part is focused on the singularity exponent evaluation for the crack impinging and generally inclined with respect to the bi-material interface. It follows the determination of the generalized stress intensity factors applying the analytical-numerical approach represented by the finite element analysis. The last part of this work is focused on the testing of algorithms applied to the specific crack and bi-material interface configurations. A conclusion discusses the influence of the bi-material mechanical properties and the angel of the crack inclination to the obtained numerical results.
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A study of the stress distribution near the sharp notch tip
Svoboda, Petr ; Majer, Zdeněk (referee) ; Profant, Tomáš (advisor)
The presented diploma thesis deals with the problem of determining the stress singularity exponent of the V-notch. This task can be divided into two parts. The first deals with the theoretical background, that means the basic relations of mechanics and the basic concepts of fracture mechanics. The second part deals with the elaboration of the Williams method and the creation of a program for calculating the stress singularity exponent.
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