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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.
11

Analýza mechanických vlastností balzového dřeva na mesoúrovni pomocí zkušebního stroje iErudio

Grossová, Olga January 2015 (has links)
This thesis analysis the mechanical properties of balsa wood mesolevel using the test machine iErudio. The thesis aim is to experimentally determine the mechanical properties of balsa wood (Ochroma lagopus). On the prototype minimachine iErudio is a set of measurements. Specifically, tensile and bending tests. Another objective is to determine the Poisson ratio on measured levels. These properties will be obtained from image data recorded device iErudio and calculated using the digital image correlation. Another objective is to evaluate the work done with the prototype device, point out the advantages and disadvantages. To analyse data using a commercial computer program VIC 3D and Mercury RT, which process the results using digital image correlation. The work has provided us with confirmation of mechanical characteristics of balsa and the suitability of using "minimachine" iErudio the performed tests.
12

Návrh a realizace zařízení pro měření síly v tahu u SMD / Design and realization of the pull strength measuring device for SMD

Valíček, Jan January 2013 (has links)
This thesis deals with the design and implementation of a device for measuring pull strength by surface mounted devices (SMD). It analyzes the theory of pull strength testing of solder joints with emphasis on standard IEC 62137-1-3 and describes the selection of components utilized to create mechanical construction and electrical parts. These electronic parts made or innovated in this work were control system based on microcontroler Atmega164P, power circuit for stepper motor and communication of measure equipment TEST 321 with PC. The whole design is complemented by simulation of mechanical stress to the critical components using ANSYS. The conclusion summarizes the most important parameters of this equipment.
13

Implementace základních metod štíhlé výroby ve výrobním podniku / Implementation of basic methods of lean manufacturing in manufacturing corporation

Holder, Jitka January 2008 (has links)
The subject of this diploma thesis is to improve the manufacturing of ISO standard valves using basic Lean manufacturing methods. Focus was at two levels, the macro level dealing with auxiliary processes for the whole manufacturing area and the micro level looking at removal of waste in the processes on one particular production cell.
14

Stabilita krystalů pevných látek z prvních principů / Stability of crystalline solids from first principles

Řehák, Petr January 2009 (has links)
This work deals with study of stability of solid crystals under isotropic loading. Ab initio methods were used for this purpose. Crystals of four fcc metals (Al, Cu, Ir, Au) and diamond were subjected to simulated isotropic tensile deformation and maximum value of isotropic stress was evaluated for them. Consequently, phonon spectra were calculated for several strain values in order to assess crystal stability. Phonon instabilities in dispersion curves of diamond, Al, Ir and Au appeared at strains lower than those corresponding to their decohesion. This appearance of instability determinates the value of ideal strength. However, significant reduction (by about 20%) was found only in the cases of Au and Ir.
15

Výpočet průhybu hřídele elektrického stroje zahrnující vliv magnetického tahu / Programme for calculation of electric machine shaft deflection caused by magnetic traction

Kukačka, Radek January 2014 (has links)
This Master thesis desires the design of methodology for calculating shaft deflection and critical speed of electric machines. There are two methods used. The first one is transfer matrix method, which is represented by a simple programme for shaft creation and calculating needed results built in the Matlab software. The second one is finite element method, which is presented in the Ansys Workbench software.
16

Komplexní analýza modálních vlastností elektrických strojů točivých / Complex Analysis of Modal Properties of Rotating Electrical Machines

Donát, Martin January 2015 (has links)
This dissertation thesis deals with the computational modelling of the dynamic response of the rotating electrical machine structure on the application of the magnetic forces. Apart from the dynamic response of the ideal symmetrical machine, the influence of the air gap eccentricity on the dynamics response is studied in this work. A basic type of the air gap eccentricity, which is caused by eccentric mounting of the rotor pack on the shaft of the rotor, is considered. The calculations the dependence of the magnetic forces on the time and a misalignment of the rotor pack are performed as first. The computational model of the magnetic field of the rotating electrical machine, which is based on solution of the electromagnetic coupled field analysis by finite element method, is used for this purpose. An analysis of the influence of the unbalanced magnetic pull and the stiffness of some parts of the machine on the modal properties of the machine is performed in the second part of this thesis. A third part of this thesis is focused on the calculation of the dynamic response of the machine during the steady state operation of the machine and the influence of the rotor pack misalignment on the dynamic response is studied. The obtained results showed that the tangential components of the magnetic forces, which act on the stator pack, excite significant torsional vibration of the stator. Besides the vibration of the stator of the machine, the influence of the rotor pack misalignment on the sound power of the machine, vibration of the rotor, loads of rotor bearings and air gap eccentricity is studied in this thesis.
17

Prvoprincipiální analýza stability krystalů pevných látek / FIRST PRINCIPLES ANALYSIS OF MECHANICAL STABILITY OF SOLID CRYSTALS

Řehák, Petr January 2013 (has links)
The aim of the author’s research in the period of his PhD study was the analysis of mechanical stability of cubic crystals under external loading. This work demonstrates several methods used for a study of mechanical stability of fcc crystals (C, Al, Ir, Pt, Au) during isotropic (hydrostatic) tensile loading. Ab initio methods were used for this purpose. Studied crystals were subjected to simulated isotropic tensile deformation and an analysis of elastic stability was performed. This analysis shows that first elastic instability in Al, Pt and Au crystals corresponds to vanishing of the trigonal shear modulus and diamond, Ir remains stable up to the state of maximum isotropic stress. According to the calculated band structure diamond crystal preserves his insulating character up to the onset of instability. Consequently, phonon spectra of all crystals were calculated using the linear response method and their dynamic stability was assessed. Obtained results reveal soft phonon modes in Al, Pt and Ir before an occurrence of elastic instability. Selected short-wavelength instabilities are confirmed using models of microscopic deformation and also using dispersion curves obtained by a supercell method. The observed instabilities lower critical strains related to the volumetric instability up to 40 % whereas the reduction of critical stress is by 20 % at the most.
18

Návrh algoritmu výpočtu rotoru elektrického stroje s ohledem na napěťově deformační poměry a kritické otáčky / Design of computational algorithm of electric machine rotor with respect to stress-strain relationships and critical speed

Pařízek, Daniel January 2019 (has links)
The Master's thesis deals with the mechanical design of electric machine rotor. Within the first two chapters of the practical part of the thesis two simplified computational models of the rotor (level 1 models) are compiled. Specifically, the model of flexible rotor mounted on rigid supports and model of rigid rotor mounted on flexible supports. The essence of these computational models lies in solvability using simple equations. Using these models can save time when constructing a pre-design of the rotor geometry. The following chapter is devoted to comparing different approaches to computational modeling of rotor using FEM. A predetermined preliminary design of a high-speed massive rotor is investigated. Computational models of different levels at stress-strain analysis and modal analysis are presented. It also includes a suggestion on how to proceed effectively in a given analysis.
19

Adheze lepených spojů fasádních obkladů z materiálů na bázi dřeva / Adhesion of Adhesive Joints for Facade Applications Made of Wood-based Materials

Nečasová, Barbora Unknown Date (has links)
The presented dissertation thesis is focused on investigating the adhesive properties of façade cladding made of wood and wood-based materials in combination with flexible adhesion/assembly systems. The systems allow the implementation of effective construction joints and provide a solution with uniform stress distribution which allows the transfer of heavy loads, while simultaneously reducing the weight of the entire structure, which is also often connected with substantial cost reductions. Despite all that, little attention has been paid to this area so far. It is not a solution which is properly embodied in technical standards or in designers´, architects´ and contractors´ awarenesses. The aim of this dissertation is to characterise adhesive properties of selected façade cladding representatives made of wood and wood-based materials for the purposes of bonded joint application in a ventilated façade system. To define adhesion of façade joints, numerical and experimental methods are used, taking also various limit conditions into account. The main conclusion of the dissertation is the characterisation of basic parameters which influence adhesion, effectiveness and quality of façade glued joints. The secondary conclusion is the compilation of a simple methodical procedure for testing and implementing façade glued joints. The dissertation also makes a contribution by extending the current state of knowledge of façade adhesive joints.
20

Analýza porušování kvazikřehkých materiálů za použití numerického modelování a akustické/elektromagnetické emise / Analysis of fracture of quasibrittle materials using numerical modelling and acoustic/electromagnetic emission

Vodák, Ondřej January 2013 (has links)
This master thesis gives overview of non-destructive tests of concrete and provides detailed information concerning the acoustic and electromagnetic emission during monitoring of concrete failure. Conducted loading tests of plain concrete specimens are described in the thesis together with the performed numerical simulations of these tests in the software ATENA. The simulation results of concrete failure are analysed in detail and compared with the experimental results recording failure processes with the help of acoustic and electromagnetic emission. The majority of simulation results in software ATENA 3D show good agreement with the recorded data.

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