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Šíření dlouhých únavových trhlin v austenitické oceli při smykových módech II a III
Holáň, Libor ; Man, Jiří (oponent) ; Polák, Jaroslav (oponent) ; Pokluda, Jaroslav (vedoucí práce)
Práce je zaměřena na realizaci experimentu umožňujícího současné zatěžování vzorku kruhového průřezu ve smykových módech II a III. Postup experimentu byl navržen tak, aby byl co nejvíce potlačen vliv zavíraní trhliny při cyklickém zatěžování a získané prahové hodnoty rozkmitu faktoru intenzity napětí tak odpovídaly efektivním prahovým hodnotám. Toho bylo dosaženo za pomocí unikátních experimentálních přípravků a postupů přípravy iniciační trhliny u vzorků s~obvodovým vrubem, vyrobených z korozivzdorné austenitické oceli. Takto získané hodnoty je poté možno aplikovat na teoretické modely s podporou molekulární dynamiky a ab inicio. Na základě získaných poznatků bylo zjištěno, že šíření trhliny v austenitické oceli probíhá dle zákonitostí dekohezního modelu. Pro kvantitativní analýzu lomových ploch vytvořených ve smykových módech II a III bylo využito metod optické chromatografie a 3D stereofotogrametrie, které umožnily srovnání morfologií, vytvořených jednotlivými smykovými módy. Pro vyhodnocení morfologie lomových ploch vytvořených (staticky, resp. cyklicky) iniciační trhlinou byly použity vybrané drsnostní parametry. V rámci experimentálních prací byl rovněž navržen mechanismus umožňující předpovídat směr vyhnutí trhliny v módu II.
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Propagation of Fatigue Cracks under Shear Loading Modes II, III and II+III in the Near-Threshold Region
Vojtek, Tomáš ; Man, Jiří (oponent) ; Polák, Jaroslav (oponent) ; Pokluda, Jaroslav (vedoucí práce)
The work is focused on fatigue crack propagation under modes II, III and II + III in the near-threshold region in metallic materials. Experiments were conducted for ARMCO iron, titanium, nickel and stainless steel on three types of specimens for shear-mode crack loading. A special technique of precrack generation was used which enabled a closure-free loading at the beginning of the shear-mode experiments. For all investigated materials the effective thresholds under the remote mode II loading were found to be about 1.7 times lower than those under the remote mode III. Tendency to local mode I branching was assessed by a measurement of local deflection and twist angles of fracture facets using stereophoto-grammetry in SEM. The lowest angles of both mode II and mode III cracks were identified for the ARMCO iron, the intermediate ones in titanium and nickel and the highest ones (pure mode I branches) were determined for the stainless steel. These differences can be explained by different numbers of available slip systems in crystal lattices of investigated materials. Ratios of measured effective thresholds in modes I, II and III were compared with results predicted by theoretical models. An analytical formula for effective mode-II thresholds was proposed and found in a good agreement with experimental results. The mode I branching criterion in terms of effective thresholds led to a critical deflection angle of 40° related to a transition from local shear to opening mode.
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Automated Inference of User Interface for NETCONF Protocol
Man, Jakub ; Orsák, Michal (oponent) ; Tisovčík, Peter (vedoucí práce)
This thesis focuses on creating a user-friendly user interface for devices that use the NETCONF protocol for configuration. A web user interface was selected to make using the user interface simple and for it to not require any additional installation. In this thesis, a user interface with a plugin architecture and with a NETCONF library was created. The NETCONF library allows users to connect devices, save them, group devices in profiles and to modify the device's configuration. The plugin architecture allows device manufacturers to provide a graphical user interface that does not require additional user training, without having to develop a whole new application.
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User Interface for DDoS Mitigation Configuration
Man, Jakub ; Kekely, Lukáš (oponent) ; Kučera, Jan (vedoucí práce)
Denial of Service (DoS) attacks is a common type of attack on internet networks and devices. A DDoS Protector device was developed to mitigate these attacks, but the configuration of this device can be complicated and requires users to be knowledgeable about the subject to configure the device to mitigate attacks effectively. This thesis focuses on providing a user interface that simplifies the configuration process of the Protector device to help less advanced users mitigate DoS attacks effectively. A web-based graphical user interface and a web application interface will be developed. The user interface will help users to configure the Protector device more straightforwardly. The application interface will allow other developers to integrate the Protector device configuration into other applications.
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User Interface for DDoS Mitigation Configuration
Man, Jakub ; Kekely, Lukáš (oponent) ; Kučera, Jan (vedoucí práce)
Denial of Service (DoS) attacks is a common type of attack on internet networks and devices. A DDoS Protector device was developed to mitigate these attacks, but the configuration of this device can be complicated and requires users to be knowledgeable about the subject to configure the device to mitigate attacks effectively. This thesis focuses on providing a user interface that simplifies the configuration process of the Protector device to help less advanced users mitigate DoS attacks effectively. A web-based graphical user interface and a web application interface will be developed. The user interface will help users to configure the Protector device more straightforwardly. The application interface will allow other developers to integrate the Protector device configuration into other applications.
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Automated Inference of User Interface for NETCONF Protocol
Man, Jakub ; Orsák, Michal (oponent) ; Tisovčík, Peter (vedoucí práce)
This thesis focuses on creating a user-friendly user interface for devices that use the NETCONF protocol for configuration. A web user interface was selected to make using the user interface simple and for it to not require any additional installation. In this thesis, a user interface with a plugin architecture and with a NETCONF library was created. The NETCONF library allows users to connect devices, save them, group devices in profiles and to modify the device's configuration. The plugin architecture allows device manufacturers to provide a graphical user interface that does not require additional user training, without having to develop a whole new application.
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MICROSTRUCTURAL INVESTIGATION AND MECHANICAL TESTING OF AN ULTRAFINE-GRAINED AUSTENITIC STAINLESS STEEL
Chlupová, Alice ; Man, Jiří ; Polák, Jaroslav ; Karjalainen, L. P.
Special thermomechanical treatment based on high degree deformation followed by reversion annealing was applied to 301LN austenitic stainless steel to achieve ultrafine-grained (UFG) structure with considerably enhanced mechanical properties. Two different conditions of the thermomechanical treatment were adopted and resulting microstructures with different grain sizes were characterised by optical and high resolution scanning electron microscopy (FEG SEM). Hardness measurements and tensile tests were performed to characterize mechanical properties. To reveal structural changes induced during thermomechanical treatment and during tensile tests a magnetic induction method was additionally applied. Experimental study validated the ability of the treatment to produce an austenitic stainless steel with the grain size of about 1.4 mu m which exhibits tensile strength of around 1000 MPa while ductility remains close to 60 %. The results obtained for both thermomechanical conditions are compared and the relationship between microstructure refinement, phase content and mechanical properties is discussed.
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