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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
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Elastoplastic analysis of stress and deformation and determination of fracture parameters of bodies with stress concentrators under tensile loading
Dubravec, Kristián ; Majer, Zdeněk (referee) ; Horníková, Jana (advisor)
The aim of this thesis is the construction of a diagram of fracture strain for high strength steel OCHN3MFA and its application for the estimation of fracture toughness of this material. The first part of the thesis contains the necessary theoretical framework for numerical modelling of tensile tests of various specimens - smooth specimen, specimen with a notch and specimen with a circumferential crack, it describes the influence of triaxiality on the fracture of bodies and the possibilities of construction of the diagram of fracture strain. Subsequently, a numerical model of these specimens is created using the finite element method (FEM). A non-linear, elastoplastic calculation is performed. Fracture is identified by means of comparing the true stress versus the strain obtained from tests with the finite element analysis results. Stress–strain states of specimens at the moment of fracture are obtained from a numerical model. A diagram of fracture strain is constructed, and it is used to estimate the fracture toughness of a cracked body. Finally, a local approach, which uses the diagram of fracture strain, and a classical approach of fracture mechanics, especially the stress intensity factor, are compared.
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Stress concentrators in aircraft structures
Černota, Jiří ; Pejchar, Jan (referee) ; Augustin, Petr (advisor)
This bachelor´s thesis deals with significant stress concentrators in compossed plane constructions made of metal materials. It generates summary of the most significant notches and their effect on fatigue life. It further states opportunities of description of constructional solution leading to reduction of stress concentration.
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Wingless/Notch crosstalk in Drosophila melanogaster
Hajšmanová, Hana ; Mašek, Jan (advisor) ; Macůrková, Marie (referee)
Fundamental for the existence of multicellular organisms is the presence signalling pathways, complex biochemical cascades, allowing reciprocal communication amongst the cells. Both Notch and Wnt pathways are crucial for embryonic development and their deregulation leads to many severe diseases. Decades of research, largely based on model organism D. melanogaster, showed that components of these pathways do not function strictly separately but on contrary interact with each other (crosstalk). This phenomenon is explored only to a lesser extent in mammals. The aim of this thesis is to recapitulate existing findings of Wnt/ Notch crosstalk in D. melanogaster and outline where crosstalk could play a role in mammals.
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Elastoplastic analysis of stress and deformation and determination of fracture parameters of bodies with stress concentrators under tensile loading
Dubravec, Kristián ; Majer, Zdeněk (referee) ; Horníková, Jana (advisor)
The aim of this thesis is the construction of a diagram of fracture strain for high strength steel OCHN3MFA and its application for the estimation of fracture toughness of this material. The first part of the thesis contains the necessary theoretical framework for numerical modelling of tensile tests of various specimens - smooth specimen, specimen with a notch and specimen with a circumferential crack, it describes the influence of triaxiality on the fracture of bodies and the possibilities of construction of the diagram of fracture strain. Subsequently, a numerical model of these specimens is created using the finite element method (FEM). A non-linear, elastoplastic calculation is performed. Fracture is identified by means of comparing the true stress versus the strain obtained from tests with the finite element analysis results. Stress–strain states of specimens at the moment of fracture are obtained from a numerical model. A diagram of fracture strain is constructed, and it is used to estimate the fracture toughness of a cracked body. Finally, a local approach, which uses the diagram of fracture strain, and a classical approach of fracture mechanics, especially the stress intensity factor, are compared.
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Studium senzitivity signální dráhy přes receptor Notch na aminokyseliny v potravě
STEFFAL, Pavel
The sensitivity of Notch signaling pathway to metabolism has been proposed in several recent studies but it is unclear if the changes in fly diet composition can directly lead to changes in Notch phenotype in vivo. In this work we show that activity of Notch pathway is sensitive to amino acids via the TOR pathway. In addition we will test a candidate protein as a sensor for amino acid level in the fat body of Drosophila melanogaster but also independently in other tissues.
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Molecular genetic basis of CADASIL disease
Hrubá, Monika ; Vlášková, Hana (advisor) ; Schierová, Michaela (referee)
CADASIL is a hereditary late-onset disease which is caused by a mutation in NOTCH3 gene. This gene belongs to the notch gene family that is conserved among Metazoa. The notch genes code transmembrane receptors which play role in Notch signal pathway during organism development. CADASIL is characterized by the impairing of small and medium vessels, especially cerebral arteries. The first symptoms appear in the middle age and the main symptoms are migraines with aura, recurrent strokes, cognitive impairment and dementia. The causes of this disease are mostly missense mutations altering the number of conserved cysteine residues in EGF-like domains of Notch3 protein. This thesis is focused on molecular genetic basis of CADASIL disease, it describes causative mutations and compares hypothesis about pathogenic mechanism of mutations. The penetration of the disease is not clarified yet but the thesis summarizes all current findings about genotype-phenotype correlations which can help to elucidate it. The phenotype differs between families and also between members of the same family. There is described the difference between men and women and the envi- ronmental influence too. There are also characterized the most common diagnostic techniques with their sensitivity and specificity in this thesis. In...
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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
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