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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Užití elektronové difrakce k mapování elastického napětí / Correlation of electron backscatter diffraction for elastic stress mapping

Ondračka, Václav January 2021 (has links)
Electron backscatter diffraction is a method that is well described and commonly used for orientation image mapping, including grain size estimation. The use of this method for measuring elastic deformation and rotations caused by plastic deformations is not so well decribed. This diploma thesis first describes the typical EBSD system. The information regarding the standard coordinate systems, grain orientation notation and system calibration is then used to create an open-source software for mapping elastic deformations and rotations inside a single grain or a monocrystal. This software uses data acquired during standard EBSD mapping on a commercial system.
62

Simulace podmínek ve výpočtech aerodynamiky vozidel / Condition Simulation in Vehicle Aerodynamics Computation

Čavoj, Ondřej January 2019 (has links)
Several types of discrepancies have been examined between CFD simulations, wind tunnel measurements and real world conditions. The results of different wheel rotation methods show that while stationary approaches can often substitute real unsteady wheel rotation, they can also be very sensitive to the exact angular positioning of wheel rims. Using both measured and computed flow fields, the lower part of wheel wake was identified as a key area, showing differences between rotation methods and sources of simulation errors in general. It was also shown that the level of detail in tyre geometry and its deformation near contact patch do not have a large impact on accuracy. Due to the absence of tyre rotation, the tyre sidewall was identified as an important place of flow separation with large effect on flow field and forces. Angle of attack study confirmed that assessing purely straight-line drag causes its under prediction compared to real-world values. This judgement would however benefit from obtaining data in more adverse conditions compared to those currently available. Finally, tyre radial expansion was investigated, causing a drop in drag with increasing vehicle velocity and altering the flow around the rear bodywork. Ignoring this effect can therefore negatively influence the aerodynamic development of a vehicle.
63

Proudy ve středních vodičích napájecích sítí a jejich důsledky / Neutral conductor loading in distribution systems. Origin and effect.

Valkoun, Petr January 2008 (has links)
This work deals with an origin of the harmonic currents, their classification into symmetrical components and their influence on neutral conductor in distribution systems. It analyses the heat strain increase in distribution cables and distortion of supply tension in consequence of harmonic zero component flows in distribution system and it provides possibilities of neutral conductor overload and break-in protection.
64

Studená chemická laminace keramiky s nízkou teplotou výpalu / Cold Chemical Lamination of Low Temperatue Co-fired Ceramics

Jurásek, Matěj January 2014 (has links)
This paper deals with production of the structures fabricated using low temperature co-fired ceramics. Focus is on the lamination of raw ceramic tapes. There are presented classical thermo-compressive methods and a new method using chemical solutions for tape bonding. Describes new lamination technology and their advantages are the absence of elevated temperatures and high pressures. This method reduces using of higher temperatures and high pressure during lamination. On the other hand, chemical process of tape bonding is not flawless. There are many problems including solvent deposition, extreme sensitivity to dust and other processing parameters. It also describes the fabrication of structures by chemical way. Specifically, analyzes the method Cold Chemical Lamination and provides examples of possible deposition solvents which are needed for etching the surface of the LTCC tape during the lamination.
65

Bezpečnostní rám závodního vozu / Race Car Roll Cage

Sedlář, Jiří January 2010 (has links)
Master thesis is about increasing of protection the crew in race car with changes in its roll-over protective structure according to current safety rules. For examination was used the Finite Element Method. The products of this thesis are different variation of roll cages, which are tasked to increasing the safety of existent race car.
66

Verifikace deformace strojního dílu / Verifikation of machine component strain

Novák, Tomáš January 2010 (has links)
The thesis deals with a comparative analysis of strain of parts using finite element method (FEM) and measurement of the optical system Pontos. Part was used the reflector of Volkswagen Polo. The subject of comparing were the values of deviations optical shield of reflector which excitation random vibration described power spectral density. The thesis presented describes of experimental measurements to obtain the boundary conditions using optical systems. FEM analysis was performed using software ANSYS Workbench 12.
67

Výroba pouzdra pružiny protlačováním za studena. / Metal formíng production of spring bush by cold extrusion.

Třeštík, Jakub January 2010 (has links)
TŘEŠTÍK Jakub: Metal forming production of spring bush by cold extrusion. The Master’s degrese project, 2nd form, summer semester, academic year 2009/2010, educational group 5O/60, Mechanical Engineering – Manufacturing Technology, Brno University of Technology, Fakulty of Mechanical Engineering, Institute of Manufacturing Technology, Dept. Of Metal Forming and Plastic, May 2010. This project sloves the manufacturing proces sof “Spring bush” part by technology of cold extrusion. Part is made of 12 122.3 steel. Semifinished product has a cylinder shape with dimensions O29-24 mm. This part is made during four bulk forming operations on the TPZK 25 Šmeral Brno, a.s.
68

Možnosti odstranění zbytkových napětí v tenkých pásech pomocí tahového rovnání / Removal of residual stress in thin sheets by tension leveling

Dymáček, Martin January 2010 (has links)
Tension leveling is a process used in the steel industry in order to eliminate any shape imperfections of cold-rolled thin strips. The master thesis deals with developing a computer program that generates basic parameters of tension leveling line. The theoretical part of the thesis summarizes the types of the shape imperfections in strips, their causes and the principles of their elimination. This part also presents the mechanism of tension leveling and describes the present-day design of tension levelers. The practical part of the thesis starts with an analytical description of stress-strain behaviour of strip during tension leveling (supposing the simplified conditions). A computer program that allows devising basic parameters of tension leveling line is created on the basis of these analytical relations. The program results are successfully verified by numerical model based on the finite element method (FEM) created in the program ANSYS. Then the interdependencies of certain input and output parameters of created program are determined. These interdependencies can be used as effective design of tension leveling lines.
69

Deformačně napěťová analýza rázem zatížené přední části automobilu. / Strain and stress analysis of the car front part under impact loading.

Hrubý, Jaroslav January 2010 (has links)
This work deals with the stress and strain analysis of the car front part of Škoda Octavia II. generation under impact loading using an explicit formulation of finite element method (FEM). The aim of this work is examination of resistance of the car front part under this impact loading and comparison of the data, which were get out of the FEM simulation of the car impact on the rigid wall with methods, which are used in forensic engineering. The comparison of the FEM simulation of the car impact on the rigid wall will be provided with the correlation method and with the method of energetic grid.
70

Studium plastických vlastností formovacích směsí / Research plasticity of foundry sands

Macků, Martin January 2010 (has links)
The subject of this thesis was to develop a comprehensive methodology for evaluating the plasticity of molding sand. This study was focused on four types of mixtures that are used in the foundry industry. For the evaluation of plasticity was important to provide an indicator of the deformation ability, calculation of deformation and logarithmic transformation for compression. Plasticity methodology was applied in this work only on the pressure effect. Studies of this issue can have a great influence on the production of correct forms due to the ability to withstand tension without breaking form.

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