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Use of 3D technology in foundry industry
Straka, Pavel ; Krutiš, Vladimír (referee) ; Pernica, Vítězslav (advisor)
The work is focused on replacing a faulty briefcase handle with an aluminium substitution. The handle is fabricated with the help of reverse engineering, where the handle is scanned with a 3D scanner. With that information, a model copy of the part is made, which is 3Dprinted from PLA and PolyCast materials. These handles are used as expendable models, which are used for casting using an “investment casting” method. Those are made from an AlSi10Mg alloy. Theoretical part deals with additive technologies, which are mostly used for manufacturing of foundry models and moulds. Next, the basic principles of 3Dscanning are described, and the term reverse engineering is also explained.
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The Roof Structure of Sport Building
Straka, Pavel ; Šmak, Milan (referee) ; Buchta, Stanislav (advisor)
The aim of the bachelor thesis is to design and assess wooden framework of roofing of multipurpose sport hall. The object is located in Moravské Budějovice. Ground plan dimensions are 40 m x 60 m and height is 10,7 m. The main load-bearing elements are full length beams, which statically acts as a double-jointed arches. The design is made of glued laminated wood, solid wood and connecting steel elements. The stability of beams is secured by purlins and transverse stiffeners. The substructure is designed with anchor blocks made of concrete situated on the foundation strips. The front walls are secured by columns and braces.
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Production of aluminum castings using metal inserts in the technology of casting into ceramic shells
Straka, Pavel ; Zemčík, Ladislav (referee) ; Krutiš, Vladimír (advisor)
The thesis is focused on manufacturing of aluminium castings with inserts by the hybrid investment casting technology. Three measures were proposed to avoid shell cracking caused by thermal expansion of insert. It seems that the covering of insert with a wax is the most efective solution, becasue after dewaxing a gap is formed, which allows insert to dilate. The other solution was based on change of molochite sand to quartz, which has a higher thermal expansion. The last mean to prevent the shell from cracking was adjustment of dewaxing cycle from shock to gradual. Ceramic shell was heated from room temperature to 650 °C. This solution did not avoid shell cracking. Then the simulation of shell heating, pouring of metal and the solidification was made. The information obtained by the manufacturing of experimental casting was used to prototype casting of impeller.
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Use of nanofiber filter for air filtration
Straka, Petr ; Hlaváč,, Jaroslav (referee) ; Kabrhel,, Michal (referee) ; Malá, Jitka (advisor)
The doctoral thesis „Using of nanofiber filter for air filtration“ is focused on application of nanofiber filter for air filtration under demanding conditions of water supply facilities. The main aim of the filter application is to decrease the secondary contamination of the indoor environment of the water accumulation tanks. The nanofiber filters are distinguished by high filtration efficiency of pollutants, dust particles and organic impurities. The contaminants don´t have to be unhealthy but they can be used for spore and microorganisms delivery to the system. They are served frequently as a reproduction substrate of microorganisms. All these factors negatively affect the water quality. The research includes formation of suitable testing methodology, pilot unit construction and operation, short-term testing and evaluation of nanofiber filters and commonly used filters and long term testing and verification of nanofiber filter attributes and quality. Furthermore the filter´s characteristics and filtration efficiency for characteristic pollutants were evaluated. Short-term and long-term experimental testing proved suitability of nanofiber filters use in water supply facilities. Interception of reported pollution indicators was reported on similar or higher level for application of nanofiber filter than for application of commonly used filter. Measured values of higher pressure difference of nanofiber filter were indicated as still adequate for use in water supply facilities. No operation difficulties, failures neither filter´s damage were reported during testing of nanofiber filters.
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Roofing of tribune
Straka, Pavel ; Horáček, Martin (referee) ; Balázs, Ivan (advisor)
The subject of this thesis was to design and assess the load-bearing structure of the grandstand roof at the sports stadium. The ground plan dimensions are 35x70 m. The object will be located in Moravské Budějovice. The construction is made of grade steel S355 and steel fasteners. Assessments were created for 2 variants. Variant A with truss, Variant B with plate girder. The truss variant, which is elaborated in more detail, was evaluated as more advantageous.
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Ultrasound desintegrator of concrements
Straka, Petr ; Čížek, Martin (referee) ; Rozman, Jiří (advisor)
This thesis is focused on the methodes of crushing kidney’s concrements with continual wave for the frequency 27 kHz and the intensity of ultrasound 10 W/cm2. The main aim is design of the ultrasound head with layer converter and design circuitry. First part of this work describes physical principle of ultrasound, ultrasound waves and methods by which could be remove kidney’s concretions. Practical part of this work is focused on compreshive design of ultrasound crushing system. In the introdiction is analyzed the proposal of applicator and the next step decscribing proposal excitation generator. The work contains results of simulation which was done on proposal curcuit, drawings of scheme, list of components and drawing of PCB.
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Návrh managementu porostů v převodu na výběrný les na ŠLP Křtiny s využitím růstového simulátoru
Straka, Prokop
On the selected area in the localities of Pokojná hora and Klepačov on the school forest company Křtiny, which are in a stage of conversion to a selection forest there was collected dendrometric data by using the measuring kit Field-Map. This data was consequently processed in the growth simulator SIBYLA, and the scenarios of the growth of the individual sample areas were created. The results of the simulations were then compared in the application STATISTICA 12. As the most suitable concept was selected the one that was closest to the ideal selection forest. It was ascertained that for the stand 109 Cav the best scenario is the Mayer frequency curve type D. For the stand 114 Cav the most suitable concept was found to be the target thickness method.
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Production of aluminum castings using metal inserts in the technology of casting into ceramic shells
Straka, Pavel ; Zemčík, Ladislav (referee) ; Krutiš, Vladimír (advisor)
The thesis is focused on manufacturing of aluminium castings with inserts by the hybrid investment casting technology. Three measures were proposed to avoid shell cracking caused by thermal expansion of insert. It seems that the covering of insert with a wax is the most efective solution, becasue after dewaxing a gap is formed, which allows insert to dilate. The other solution was based on change of molochite sand to quartz, which has a higher thermal expansion. The last mean to prevent the shell from cracking was adjustment of dewaxing cycle from shock to gradual. Ceramic shell was heated from room temperature to 650 °C. This solution did not avoid shell cracking. Then the simulation of shell heating, pouring of metal and the solidification was made. The information obtained by the manufacturing of experimental casting was used to prototype casting of impeller.
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Modification of the Algebraic Transition Model for Wall Roughness Effect Including a Rough Strip
Straka, P. ; Příhoda, Jaromír
The contribution deals with the simulation of the laminar/turbulent transition on a rough wall. The algebraic transition model taking into account wall roughness according to Straka and Příhoda [8] was further extended for the effect of short rough strip near the leading edge. The proposed correlation was tested by means of incompressible flow over a flat plate covered by sand paper and around the NACA 0012 airfoil with a rough strip near the leading edge. The agreement with experiments is appropriate nevertheless the applicability of the correlation is limited due to the lack of relevant experimental results.
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