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Micro-turning applications in high precision manufacturing performed by diamond tools
Švorc, Josef ; Dvořák, Jaromír (referee) ; Žídek, Jan (advisor)
Bachelor thesis is focused on micro-turning. The work takes the form of a literary research, which aims to make an overview of the production technology. First, it deals with the definition of the topic itself and with the physical properties and phenomena that occur during micro-machining. Then it discusses the construction of micro lathes and their division into categories and compares them to each other. It also deals with the cutting tools suitable for this machining process and their production and shaping. The last part of the thesis is focused on the application and utilization of micro-turning in industry and on the creation of non-rotational components and micro-structures.
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Productive milling of aluminum alloys
Dvořák, Jakub ; Žídek, Jan (referee) ; Jaroš, Aleš (advisor)
This bachelor thesis is focused on milling of aluminum alloys, where the technology of milling is described in the first place, then the cutting materials and aluminum alloys. The main subject of the work was to carry out the experiment. The Experiment was focused on influence of cutting conditions on the final quality of the surface with regard to machine time. The aluminum workpiece was milled at different cutting speeds and various feed per tooth. At the same time the quality of the surface was examened and machine times were calculated. The Experiment showed us, whether it pays to use higher cutting speeds and feed per tooth, keeping the set of limited values of surface roughness with respect to the machine time. The result of the experiment is the following - the increasing feed per tooth deteriorates the quality of machined surface, but machine time is reduced.
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Reactive Modification of Polypropylene
Matláková, Jana ; Žídek, Jan (referee) ; Lehocký, Marián (referee) ; Kučera, František (advisor)
The theoretical part describes the principles of the free-radical induced grafting and the influence of various parameters on the reactions course. The literature research summarizes the latest knowledge in the field of the reactive modification of polypropylene (PP), it is mainly focused on the PP modification using an unsaturated acid anhydrides. Theoretical part describes the various procedures and modification of technology in order to increase the grafting yield of maleation. The experimental part is determined by the influence of the stabilizers concentration, the peroxide structure, and the binary mixture of monomers on the grafting yield and the reaction course. In the first part, the critical stabilizers concentration was determined based on the experimentally obtained relationship between the grafting yield and the stabilizers concentration. A kinetic schema of grafting of MAH onto PP in the presence of stabilizers has been proposed and compared with the experimental results. The effect of the stabilizers on the extent of the undesirable b-scission was evaluated based on the melt flow rate (MFR) and the rheological curves of PP-g-MAH. In the second part, the effect of the peroxide structure and the concentration of reactants on the grafting yield of PP modification with MAH and itaconic anhydride (IAH) was observed. The initial grafting yield Rg has been experimentally determined and compared with a defined area of theoretical values of Rg. The extent of b-scission was significantly influenced by the structure and the concentration of peroxide, as shown by the results of MFR and the rheological curves of PP-g-MAH. The last part of the doctoral thesis is focused on the assessment of the combination of MAH and IAH as comonomers on the grafting yield. At first, the reference polymers were prepared using the solution polymerization of MAH, and IAH, and copolymerization of MAH with IAH. The reference polymers were analyzed by FTIR, DSC, WAXS to confirm the probable copolymerization of MAH and IAH. The dependence of the reaction enthalpy on the reaction time was observed using simulations of bulk polymerization of MAH, IAH and mixtures MAH and IAH "in situ" in isothermal calorimeter. PP was subsequently modified with a combination of MAH and IAH as comonomers in order to assess its effect on the grafting yield
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Effects of structural and processing parameters on th eproperties of polymer nanocomposites
Zárybnická, Klára ; Žídek, Jan (referee) ; Jančář, Josef (advisor)
The work deals mainly with preparation protocol of nanocomposites. The task of this work is to study structural and procedural parameteres that control the dispersion of nanoparticles in polymer solution to be able to prepare desired spatial organization of nanoparticles. The work resolves the effect of various components such as polymer matrices, nanoparticles and solvent, in which matrices and nanoparticles are blended. Used components control final dispersion state of nanoparticles and it influences also properties of investigated materials such as glass transition temperature, stiffness and rheological properties.
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Bioresorbable polyurethanes with controlled mechanical properties
Letavaj, Emil ; Žídek, Jan (referee) ; Kupka, Vojtěch (advisor)
Presented diploma thesis deals with preparation of bioresorbable polyurethanes (PUR) and their characterization. The theoretical part describes the feedstocks used for the PUR preparation and summarizes the knowledge about PUR used in medical applications. Experimental part presents characterization of bioresorbable PUR films prepared by reactive casting in one step without the use of organic solvents. The absence of solvents represents a great advantage due to their toxicity and subsequent removal from the resulting product. The synthesis of PUR was conducted under an inert atmosphere by polyaddition reaction of hydrophobic poly(e-caprolactone) (PCL) and hydrophilic poly(ethylene glycol) (PEG) with hexamethylene diisocyanate (HDI). Synthesis under an inert atmosphere was necessary due to a side reaction of isocyanate with atmospheric humidity, which causes the formation of porous films instead of continuous ones. Prepared PUR films were characterized for different PCL/PEG ratios and different isocyanate index (ratio of NCO/OH reacted groups). PUR (isocyanate index 1.05) with PCL content 90 wt. % and higher demonstrated tought behavior in mechanical tests. Increase of isocyanate index and decrease of PCL content under 90 wt. % caused fragile sample behavior. The reason of such behavior was the different ability of PCL to crystallize in the structure of the polyurethane network. Increasing the PEG content has improved the ability of PUR films to absorb water and enhanced the rate of hydrolytic degradation. By adjusting the PCL/PEG ratio and the amount of isocyanate, solvent free bioresorbable PUR with suitable mechanical (flexibility, toughness) and physical properties (swelling, degradation) can be obtained. Prepared PUR films could be used in biomedicine e.g. as vascular grafts.
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Quality assessment of the OpenStreetMap data in Prague
Zídek, Jan ; Moudrý, Vítězslav (advisor) ; Šímová, Petra (referee)
OpenStreetMap (OSM) is the largest and objectively the most successful project from all attempts to open-source alternative to commercial map databases and projects of the official agencies. OSM is widely popular in Czech Republic, but the quality of this VGI (volunteered geographic information) dataset has not yet been studied. This master thesis evaluates several aspects of quantifiable characteristics of buildings in Prague. The objective was to primarily evaluate completeness, semantic accuracy and shape accuracy of building footprints. Data from OSM were compared with Digital map of Prague by Geoportal Prague, which is the official map resource covering the area of the city Prague. The data processing was done in ArcGIS by the ESRI company. The results show that OSM in Prague have high semantic accuracy and almost 100% completeness in terms of total area, but more than 50% of buildings are missing basic descriptive data. In terms of shape accuracy the footprints were identified by smaller amount of vertices than the footprints from Geoportal Prague and in some cases certain architectural details were missing.
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Data processing for tomographic reconstruction
Dospiva, Jindřich ; Žídek, Jan (referee) ; Zikmund, Tomáš (advisor)
This thesis deal with data processing from x-ray tomographic system. The primary focus is put on the description of projection refining taking place before tomographic reconstruction. The particular method for data processing from system Nano3DX is also suggested. It uses open software ASTRA tomography toolbox, which enable executing of tomographic reconstruction on the graphics card in MATLAB environment. There is also used correction for sample movement, denoising algorithm in projections and calculation the centre of rotation. Results of proposed procedure are demonstrated on tomographic data from measured samples and compared with processing software from the manufacturer.
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Modelling of Chemical Processes
Al Mahmoud Alsheikh, Amer ; Bártlová,, Milada (referee) ; Urban,, Ján (referee) ; Žídek, Jan (advisor)
V této práci je prezentována studie fragmentačního procesu zvolené molekuly a jeho vztah ke složení fragmentačních produktů. Práce je zaměřená na výpočet fragmentační energie molekuly pomocí ab initio kvantově chemických metod, metodou „density functional theory (DFT)“ a také srovnáním s experimentem. Je prezentován vliv výpočetní metody, bázového setu, a geometrie molekuly na simulaci. Byla porovnána fragmentace methylfenylsilanu (MPS), dimethylfenylsilanu (DMPS), a trimetylfenylsilanu (TMPS). Fragmentace byla iniciována monochromatickým elektronovým svazkem (EII). Hmotnostní spektrometrie byla využita ke studiu složení fragmentačních produktů MPS a TMPS. Fragmentační produkty MPS a TMPS měřené v rámci této práce byly doplněny o experimentální studii DMPS, která byla prezentována v literatuře. Takto byla získána řada molekul, které jsou strukturně podobné, ale mají výrazně rozdílné chování během fragmentace. Pomocí měření účinného průřezu byly měřeny disociační energie vazeb a tyto disociační energie byly vypočteny pomocí metody DFT. Kombinací teoretického výpočtu metodou DFT a experimentálního měření jsme poukázali na společné rysy a na rozdíly ve fragmentačním schématu všech tří molekul. Navrhli jsme odštěpení dvou vodíkových atomů během plazmově indukovaného fragmentačního procesu. Vodíky mohou být odštěpeny pomocí dvou mechanismů: i. odštěpení dvou vodíků jeden po druhém a ii. odštěpení molekuly H2 v jednom kroku. Z profilů energie dokážeme určit, který mechanismus bude v tom konkrétním případě pravděpodobnější. Předpokládaný mechanismus je v korelaci s experimentálními výsledky fragmentace zjištěnými z hmotnostních spekter.
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On the deburring technology of a formed part
Žídek, Jan ; Polzer, Aleš (referee) ; Píška, Miroslav (advisor)
This diploma thesis was created in cooperation with Mubea company. It deals with proposal of alternative technology of groove deburring. A special tool was designed for this technology and was experimentally tested. There are also tests for finding suitable cutting conditions, tests for appropriate tool’s positioning against a workpiece and tests for comparison the alternative technology of groove deburring to grinding technology included in this diploma thesis
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Study of Relation between HDPE Internal Structure and Its Cut Growth Resistance SCG (Slow Crack Growth)
Chladil, Martin ; Žídek, Jan (referee) ; Petrůj, Jaroslav (advisor)
This thesis deals with the relation between structure and resistance to failure by the mechanism of slow crack growth (SCG) in HDPE. In the theoretical part there are summarized previously acquired knowledge about the production of PE and about the relation between structure and resistance to failure by the SCG mechanism. In the experimental part, three samples of HDPE with the same melt index MI and the same content of copolymer 1- hexene were synthesized by using three chromium catalysts commonly used for polymerization in industry. There samples were analyzed by GPC-IR-MALS and TREF in order to determine the distribution of side chain branches. The results were discussed with respect to the time to failure FNCT.
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