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The fatigue life of steel specimens under axial, torsional and combined axial-torsional loading
Mička, Jan ; Horníková, Jana (referee) ; Slámečka, Karel (advisor)
The master’s thesis deals with the fatigue life prediction under multiaxial cyclic loading. First, the fatigue process is discussed and the methods for fatigue life prediction under uniaxial and multiaxial loading are described. In the practical part, the accuracy of selected criteria is assessed based on experimental data obtained on cylindrical samples made of 1.2210 steel that were tested under synchronous symmetric axial-torsion loading. Application of criteria requires to determine the fatigue strength under pure axial and torsional loading.
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Description of Stress and Strain States at the Front of Cracks Loaded by Shear Modes
Žák, Stanislav ; Majer, Zdeněk (referee) ; Horníková, Jana (advisor)
The main goal of this work is the comparison of the size of the plastic zone at the crack tip for two analysis methods: an analytical linear method and an elastic-plastic analysis employing the Finite Element method (ANSYS software). All calculations were made for a crack loaded under pure shear modes. These types of loading are not sufficiently described in the literature. The first part of this work introduces the problem with the crack tip plastic zone using both linear and nonlinear fracture parameters. The second part is dedicated to the construction of the Finite Element model in the ANSYS software. The geometry of the samples and the loading levels were chosen to match an existing experimental test of the impact of shear modes on the crack behavior. In the third part of this thesis, the plastic zone radii for pure shear modes II and III are estimated using several methods and the results are compared. In the last part of this work, the same procedure as in the previous part is applied on a mixed-mode II+III loading. A result of this thesis is the assessment of the application limits of the linear analysis method used to estimate the size of the plastic zone at the crack tip for a specific geometry and material model.
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Comparison of fatigue fracture criteria for torsion
Roh, Marek ; Slámečka, Karel (referee) ; Horníková, Jana (advisor)
The main goal of this bachelor thesis is to determine which criteria better suits the life prediction of the test sample loaded in the pulsating torsion. In the first part of this thesis fatigue failure will be examined, then fluctuating stresses will be characterized along with shear stress. Characteristics of the materials used will be specified in the second part. Lastly, the most appropriate criteria will be determined.
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Comparison of fatigue fracture criteria for uniaxial tension
Stolář, Jakub ; Šebek, František (referee) ; Horníková, Jana (advisor)
Bachelor’s thesis „Comparison of fatigue fracture criteria for uniaxial tension“ is focused on material fatigue and the possibilities of material service life aproximation for uniaxial tension. Research study of material fatigue and fatigue fracture criteria is stated in the first part of the thesis. In the second part, experimentally measured data are processed and application suitability of particular fatigue fracture criteria is assessed while using the research study theoretic findings.
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Assesment of stress strain response during cyclic loading
Lehnert, Ondřej ; Slámečka, Karel (referee) ; Horníková, Jana (advisor)
This bachelor´s thesis is focused on assessment of data extracted from testing machine and establishment of cyclic stress-strain curve using peaks of saturated hysteresis loops. In this thesis before data analysis itself, is written down research study about general fatigue of material, then the study is focused on change of mechanical attributes, description of hysteresis loops and cyclic curve. After that follows the procedure of data analysis extracted from testing machine aimed to compare cyclic curve with tensile curve and its mathematical description.
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Criteria of Multiaxial Fatigue Life
Blaha, Jakub ; Slámečka, Karel (referee) ; Horníková, Jana (advisor)
Bachelor’s thesis is about fatigue of materials and options of component’s lifetime determination during multiaxial cyclic loading. First it is described mechanism of initiation and grow of fatigue cracks, then the way of determination fatigue life during uniaxial loading and state of stress during multiaxial loading. Then multiaxial fatigue criteria for life time determination are presented. All criteria are based on critical plane and are divided into stress-based, strain-based and energy-based.
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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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