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Development of a New Generation of Devices with Advanced Diagnostics for Determining Contact Degradation
Dvořáček, Jiří ; Hájek, Karel (referee) ; Náhlík, Luboš (referee) ; Pazdera, Luboš (referee) ; Mazal, Pavel (advisor)
The thesis proposes a methodology for damage identification of thrust bearings using acoustic emission method. The work is the way of the hydraulic loading of specimens and thrust bearings with programmable settings severity and duration of load cycles during contact fatigue tests at stations Axmat. They are designed structural adjustment elements (waveguides) to capture the acoustic emission signal selected apparatus, including the modification of software to capture the data. At the described experiments is verified functionality of the circular test specimens and axial bearings . Part of this work is to propose a new methodology for identifying early stages of contact fatigue using a combination of diagnostic methods.
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PROPAGATION OF LONG FATIGUE CRACKS IN AUSTENITIC STEEL UNDER SHEAR MODES II AND III
Holáň, Libor ; Man, Jiří (referee) ; Polák, Jaroslav (referee) ; Pokluda, Jaroslav (advisor)
This work is focused on the realization of experiment allowing simultaneous loading under mode II and III in a single circular specimen. Proposed experiment allowed to minimize crack closure during the cyclic loading and obtained values of thresholds of stress intensity range can be considered to be very close to effective values. This was attained by means of an unique experimental devices and procedure of preparation of pre-crack of specimen with circumferential notch, which was made of stainless austenitic steel. The obtained values were compared with theoretical models with the support of molecular dynamics and ab-anitio calculation. Based on observation was found out, that fatigue crack propagation is controlled by decohesion model in austenitic steel. The morphology of fracture surfaces was studied by means of optical chromatographie and 3D stereophotogrammetry, which allowed a comparison of created morphology under shear modes II and III. Morphology of fracture surface formed (static and cyclic loading) by pre-crack was also studied by means of selected roughness parameters. The mechanism of deflection (kink) of crack growth under mode II was defined.
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Modification of Diffusive Gradient in Thin Films Technique for Characterization of Environmental Systems
Gregušová, Michaela ; Sommer, Lumír (referee) ; Janoš, Pavel (referee) ; Dočekal, Bohumil (advisor)
Diffusive gradient in thin film technique (DGT) represents a relatively new approach for in situ determinations of labile metal-species in aquatic systems. The DGT device passively accumulates labile species from the solution while deployed in situ, and therefore contamination problems associated with conventional collection and filtration procedures are eliminated. This study deals with a possible modification of DGT technique. The key of using DGT technique for speciation analysis of metals is to find out suitable binding phase and diffusion layer. The new resin gel based on Spheron Oxin (5 sulphophenyl-azo-8-hydroxyquinoline) ion exchanger with a higher selectivity to trace metals than Chelex 100 could potentially provide more information on metals speciation in aquatic systems. The performance of this new binding phase was tested for the determination of Cd, Cu, Ni, Pb and U under laboratory conditions. The hydrogel layer based on poly(2-hydroxyethyl methacrylate) was synthesized and tested as a new diffusion gel for application in DGT technique.
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Design of Device for Regrinding of Specimens
Matečka, Martin ; Nečas, David (referee) ; Smejkal, David (advisor)
This bachelor thesis is focused on design of device for regrinding of specimens. In the first part is described grinding technology, cutting conditions for grinding of outer cylindrical surfaces and kinematic and dynamic phenomena arising in these conditions. There are also analyzed the grinding tools and their using. In the next points are described the designs of the grinder’s basic components. The last in this chapter is described the testing device on which the specimens are tested. The next chapter is focused on description of the objectives and analyzing the problems. There are described the variants of design solutions. After assessment of advantages and disadvantages of all variants is selected optimum design solution which is detailed described in the last section.
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Design of surface texturing experimental rig
Bouma, Adam ; Svoboda, Petr (referee) ; Šamánek, Otakar (advisor)
The aim of this thesis is mechanical indenter design, mainly two basic parts of this apparatus. The introductory section describes the basic techniques of mechanical surface texturing of engineering surfaces. The second part deals with the particular design of the device. It also describes the strength control of loaded components. The economic evaluation is given at the end.
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Thermal Dilatation Measurement of Elastomeric Plastic Sheets
Mahel, Jindřich ; Kučera, Jaroslav (referee) ; Petrůj, Jaroslav (advisor)
The aim of the thesis was to design and build an apparatus for measuring linear thermal expansion of plastic waterproofing sheets. In the theoretical part of the thesis the methods used for measuring linear thermal expansion of solids were compared and the principle of thermoelectric cooling was described . For the measuring the Abbe comparator has been chosen , which has been equipped with a tempered chamber with a cascade of thermoelectric Peltier elements for cooling and heating of specimen. The experimental part of the thesis deals with the construction of the device and the actual measuring in the specified temperature range.
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Manufacturing of Components Using Rapid Prototyping
Peňáz, Jan ; Sedlák, Josef (referee) ; Kalivoda, Milan (advisor)
The bachelor thesis deals with solution of manufacturing prototype using three technologies. Two of them are additive technologies using principles of Laminated object manufacturing and Fused deposition modelling. The third technology was milling. Model of reversible turbine was used as a base for manufacturing. CAD system SolidWorks was used for the model creation, where output formats were SLDPRT and STL. For error check of STL data software MiniMagics was used. For preparation of 3D printing data softwares SD View and Catalyst EX were used. CAM system SolidCAM was used for creation of machining strategy. Devices used for manufacturing of prototypes were 3D printer Solido SD 300 Pro, 3D printer Stratasys uPrint and 5axis mill Hermle C20U. Print on 3D printer Stratasys uPrint the most advantageous technology for manufacturing one prototype.
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Assessment of fish contamination in important fishing grounds
ČERVENÝ, Daniel
The object of this thesis is the assessment of fish contamination by selected foreign substances as toxic metals, polychlorinated biphenyls and pesticides in 31 selected fishing grounds. The monitoring was realized between years 2006 and 2010. Fish were caught by electric device and fishing rods. Concentrations of Hg, Cd, Pb, PCB, DDT, HCH and HCB in fish muscle tissues were monitored. Common bream (Abramis brama) was selected as a reference species for a comparison of the monitored sites. The results of analysis were compared with valid hygienic limits. Overrun of hygienic limit for some of the monitored pollutants were observed in 18 localities. We found mercury as a major pollutant in the aquatic environment.
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Magnetic anisotropies in (Ga,Mn)As and metallic multilayers with strong spin-orbit coupling
Zemen, Jan ; Jungwirth, Tomáš (advisor) ; Diviš, Martin (referee) ; Šob, Mojmír (referee)
The thesis presents a numerical study of magnetocrystalline anisotropies in dilute ferromagnetic semiconductors and transition metal systems intended to advance the current understanding of the microscopic origins of this relativistic effect and to contribute to the development of spintronic devices with new functionalities. The major part of the work surveys magnetocrystalline anisotropies in (Ga,Mn)As epilayers and compares the calculations to available experimental data. Our model is based on an envelope function description of the valence band holes and a spin representation for their kinetic-exchange interaction with localised electrons on Mn2+ ions, treated in the mean-field approximation. For epilayers with growth induced lattice-matching strains we study in-plane to out-of-plane easy axis reorientations as a function of Mn local-moment concentration, hole concentration, and temperature. Next we focus on the competition of in-plane cubic and uniaxial anisotropies. We add an in-plane shear strain to the effective Hamiltonian in order to capture measured data in bare, unpatterned epilayers, and we provide microscopic justification for this approach. The model is then extended by an in-plane uniaxial strain and used to directly describe experiments with magnetisation direction controlled by...
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