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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.
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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.
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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.
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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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Influence of torsional pre-strain on fracture characteristics under tensile loading
Kupka, Oldřich ; Majer, Zdeněk (referee) ; Horníková, Jana (advisor)
The diploma thesis is about the influence of torsional pre-strain on fracture characteristics under tensile loading of steel 11 375. Plastic strain in the cross-section of tested specimen is caused by torsional pre-strain. Plastic strain causes a different response of a material to tensile loading. A smooth tensile test specimen and tensile test specimen with a notch are examined. The research part of thesis describes tensile and torsional tests according to regular standarts. The nonlinearities considered in computational models are also described, followed by a description of material models in the software Ansys, which is used to create the computational model. Mechanisms of failure, the importance of stress triaxiality and the construction of triaxiality space are also introduced to a reader. The first experiment is about a tensile test of steel 11 375. The stress-strain curve obtained by the tensile test will be used as input in computational modelling. The aim of computational modelling is the determination of torsional pre-strain, that causes plastic strain in a tested specimen. The true stress field, true strain field and points of triaxiality space are determined by computational models. During the second experiment, tensile test specimens are torsioned according to outputs of computational models, followed by a tensile load to fracture. The main output of the experiment is fracture engineering strain. Finally, the stress-strain curves of computational models are also compared with experimental measurements.
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