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Pilový kotouč v procesu podélného řezání materiálů na bázi dřeva
Veselý, Přemysl
In this dissertation thesis there is listed characteristics of circular saw blades, their distribution, influence of construction adjustments on final behavior of blade in the process of machining, problematic of oscillation of blades a mutual interaction among quality of machined surface, noise and dust. The thesis covers the problems of oscillation of circular saw blades as when idling and operating - the cutting process; and by the use of three circular saw blades with different construction modifications. These aforementioned construction measures are also compared to each other due to the implementation of standard construction saw blades not only from the perspective of oscillation, but also from the perspective of the roughness of the machined surface and the analysis of wood waste generated during cutting and noise. In the theoretical part there is an analysis of available literature and scientific theses. It outlines the particular publications devoted to methods of determining the shapes of oscillation, determining critical, resonant and recommended speed, blade constructions, including possible modifications, the theory of cutting saw blades including determining the size and shape of the splints and the effects of noise on the work environment. An important part of this work is methodology involving direct measurements for detection of unstable states of discs (resonance and critical speed. In this section it is further evaluated measuring of the oscillation of the test saw blade and verification of the proposed methodology with a different and practiced, commonly known method, so called cold shapes: The author also seeks to explore and determine the effect of different tooth pitch and method of execution of slots along with soundproofing grooves on noise levels, the resulting quality of the machined surface of various wood. The generated waste is then analyzed for splitting wood particles in particular size group with the percentage of each chip. The results of the experiment are in discussion confronted with the available scientific theses, taking into account with normal operating conditions, of which the conclusion is drawn.
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Frequency analysis of the blades of the steam turbine impeller
Krejčí, Jaroslav ; Chromek, Lukáš (referee) ; Lošák, Petr (advisor)
The master thesis deals with modal analysis of the blade of the steam turbine impeller. This analysis is made to find the frequency response of the blade in order to predict the dangerous speeds of the steam turbine. At first the problem situation is described. Than follows the research study which is focused on steam turbines and especially on the rotor dynamic systems and the way to ascertain the modal parameters of the dynamic system by experiment. After that the solution of the problem is performed by computational modelling. The results of the computation are analyzed in detail for different variations of the blade length by Campbell diagram. A graph showing dependency between dangerous speeds of the turbine and the blade length is made out of the results. Then the results are verified by experiment and the coefficients of proportional damping are specified. In conclusion the optimal variation of the blade length for the given operational state is determined.
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Comparison of modal properties of steam turbine impeller with blades of different lengths
Havlásek, Michal ; Chromek, Lukáš (referee) ; Lošák, Petr (advisor)
The presented master's thesis deals with the safety assessment of several variants of the impeller with different blades length. The motivation for creating this thesis is to find the solution of the problem situation which is characterized by the breakdown of the steam turbine impeller with blades length of 30mm. As confirmed in this thesis, the impeller with blades length of 30mm is operated in the resonance. Likewise, according to the technical standard ČSN EN ISO 10437 its operation is not safe. As the correction action for the problem situation solving is proposed the prolongation of the impeller's blades. The safety is detected for six variants of impeller with dierent blades length. For each variant, there is executed a modal analysis and its results are drawn up into the Campbell diagram. On the basis of this diagram, the safety of individual components is evaluated. The last part of the masters thesis concerns with the examination of the influence of blades length on the modal properties of the impeller.
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Analysis of mechanical behaviour of synchronous generator
Donát, Martin ; Hadaš, Zdeněk (referee) ; Dušek, Daniel (advisor)
This Master’s thesis deals with analysis of mechanical behaviour of the synchronous generator and assessment of the possibility of reducing the mass of the frame of the generator. The aims of this work were: to perform the stress-strain analysis and modal analysis of the required model of the synchronous generator, to assessment influence of single part of the frame of the generator over its stiffness and design construction modification of the frame of the generator, which reduce its mass.
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Dynamic Behavior of Laval Rotor
Nováková, Naděžda ; Hlavoň, Pavel (referee) ; Malenovský, Eduard (advisor)
The aim of this bachebor’s thesis is to specify self-frequency of model rotor system and verify that the system may be considered as Laval rotor. The natural frequency is obtained by calculating from the known relations for the circular rotor vibration. Verify that the model rotor system can be Laval rotor, is performed by using experimental measurements, which is determined in shaft deflection trajectory during gradually increasing speed. The measured values are then processed in program MATLAB. The results are compared with theory of Laval rotor
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