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The use of hydraulic disc brakes for road bikes
Dvořáková, Barbora ; Lošák, Petr (referee) ; Šebek, František (advisor)
This bachelor's thesis is focused on the usage of hydraulic disc brakes on road bikes. The thesis is divided into two parts. In the first part, there is a research focused on differences in construction and properties of hydraulic disc brakes in comparison with rim brakes. The main emphasis is placed on evaluating all advantages and disad-vantages of the hydraulic disc brakes in comparison with rim brakes. Evaluation is conducted both from the functional point of view and user point of view with taking different requirements of both recreational level cyclist and professional cyclist into account. The aim of the second part is the numerical simulation of loading of the frame and fork for both types of brakes. The goal of this part is an overall assessment of suitability of hydraulic disc brakes for the road bikes.
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Analysis of the rotor packet prestress on the rotor critical speed
Lekeš, Filip ; Huzlík, Rostislav (referee) ; Lošák, Petr (advisor)
The presented diploma thesis deals with the modeling of the rotor packet in dynamic calculations and analysis of the influence of the packing pressing force on the critical speed of the electric motor. The thesis can be divided into three main parts. The first part discusses the current level of rotor packet modeling in dynamic calculations and also deals with analytical theories for subsequent experimental tests. The second part describes the implementation of two experiments to determine the equivalent modulus of elasticity. The first experiment is a four-point bending test and the second is an experimental modal analysis. The third part is used for comparing the results obtained from experimental tests and describes the calculation of the critical speed of the rotor package pressed on the shaft by the finite element method.
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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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Dynamic model of nonlinear oscillator with piezoelectric layer
Sosna, Petr ; Lošák, Petr (referee) ; Hadaš, Zdeněk (advisor)
Tato diplomová práce je zaměřena na analýzu chování magnetopiezoelastického kmitajícího nosníku. V teoretické části jsou odvozeny diskretizované parametry, které popisují reálnou soustavu jako model s jedním stupněm volnosti. Tento model je následně použit pro kvalitativní i kvantitativní analýzu chování tohoto harvesteru. Frekvenční odezva harmonicky buzeného systému je zkoumána v dvouparametrické nebo tříparametrické analýze v závislosti na amplitudě buzení, elektrické zátěži a vzdálenosti mezi magnety. Posledně zmíněný parametr je v práci tím hlavním, proto je vliv vzdálenosti magnetů zkoumán také s pomocí bifurkačních diagramů. Tyto diagramy byly navíc použity k vytvoření oscilační "mapy", která pro každé zatěžovací podmínky ukazuje, jakou vzdálenost magnetů je třeba nastavit, aby bylo generováno nejvíce energie. Práce je doplněna o ukázky několika jevů, které mohou značně ovlivnit chování systému, pokud se nejdená o čistě harmonické buzení.
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Design of separator
Benda, David ; Nekvasil, Richard (referee) ; Lošák, Petr (advisor)
This diploma thesis deals with design of the gas separator according to the standard ČSN EN 13445. The design is based on the specified operating parameters and the basic dimensions, including the individual positions of the connecting flanges on the device according to the relevant schema. The assignment also includes the load of the nozzles from connected pipelines to the device. The analytical calculation of the design is performed in the commercial software NextGen with the analysis of the individual components used. Furthermore, some parts of the device are inspected in detail using the finite element method in the commercial software Ansys. The thesis also included the drawing documentation of the designed gas separator.
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Interier Vibration Analysis of Moving Train
Železník, Gabriel ; Lošák, Petr (referee) ; Hadaš, Zdeněk (advisor)
In this work, a multibody system of a passing train on a railway is created. The model is focused on the vibrations, which are related to defect conditions. The subject of this work is to investigate the effect of vibrations in the interior of a rail vehicle. In the first part of the work, research of published dynamic models is performed. Various options for track and train modeling are described. Furthermore, the research presents several solution methods that can be used to simulate the moving train. Based on the research, the structure of the model and the method of solution were determined. The main areas of interest are the track, on which vibrations occur in contact with the wheel, and the car body, in which the vibrations will be further analyzed. For this reason, both parts were modeled as flexible bodies. The assembled model uses finite element discretization to describe flexible bodies. The time domain simulation is done by using generalized coordinates and modal superposition. The work describes the construction of the model in detail. The whole model is written in the Matlab and all codes are part of the appendix. The model allows change of all the parameters of the track and the car, including their geometric dimensions. The model includes 4 excitation mechanisms simulating the following defects: flat wheel, lifted sleeper, damaged sleeper and rail wear. After the model algorithm is fully described, the simulations without any defect are performed and a behavior of each system component is described. Finally, simulations of defect conditions are performed. Thanks to the combination of all defect conditions the response of the car body for the analysis of vibrations in the interior is compiled. In the last part, the compiled response in the frequency domain is used for the analysis of random vibrations in the vehicle interior in the Ansys environment. A 3D model of the train's ceiling paneling is used for the analysis, on which the effects of static and dynamic loads are compared. The area with the highest stress was determined by random vibration analysis. In the end, the modification of the part is proposed, which leads to the improvement of the strength properties of the assembly.
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Modal Analysis of the Swirl Turbine Rotor Blades
Pekar, Marek ; Chromek, Lukáš (referee) ; Lošák, Petr (advisor)
The aim of this diploma thesis is to determine and compare modal properties of four swirl turbine wheels, each with a different geometry. Natural frequencies and mode shapes were obtained based on computer modelling using Ansys software and they were compared with experimental modal analysis' results. The computer modelling and the experimental modal analysis were carried out for different boundary conditions and in different environments. The beginning of the thesis is dedicated to a brief overview of literature with similar issues. Then a brief introduction of a dynamics theory is mentioned in which equations of motion for a damped and an undamped single degree of freedom system are derived. The creation of a geometry model which is obtained by a reverse engineering is shown in the second part of the thesis. The geometry model was subsequently used for the computer based modelling of the modal parameters. In the third part an experimental equipment, setting, measurement and processing of data are described. The conclusion of the thesis is dedicated to the comparison of the results obtained by the experimental modal analysis and the computing modelling is presented. Moreover, influence of boundary conditions and influence of the environment on the natural frequencies are evaluated.
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Use of Neural Networks for the Stiffness Calculation of a Spur Gear Transmission
Planka, Michal ; Krpalek, David (referee) ; Lošák, Petr (advisor)
The aim of this master's thesis is to build artificial neural network that is able to calculate varying single tooth-pair mesh stiffness of spur gear for given input parameters. The training set for this network was determined by computational modelling by finite element method. Therefore, creating of computational model and mesh stiffness calculating were a partial aim of this thesis. Input parameters for stiffness calculation were number of driving and driven gear teeth and gear loading. Creating of computational model and performing series of simulations was followed by creating artificial neural network. Multilayer neural network with backpropagation training was chosen as a type of the network. Created neural network is sufficiently efficient and can determine varying mesh stiffness in input set range for learned input parameters and for values of parameters that are not included in training set as well. This neural network can be used for varying single tooth-pair mesh stiffness estimation in input set range.
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Topology optimization of the rocker in the shoe making machine
Gargulák, Jiří ; Ševeček, Oldřich (referee) ; Lošák, Petr (advisor)
Topology optimization, SIMP, LSM, Ansys, experiment, data processing, analysis, model
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