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The modal damping ratio analysis of the mechanical part using the OMA method
Sodomka, Tomáš ; Lošák, Petr (referee) ; Houfek, Lubomír (advisor)
In one of the first hours of study at the Institute of Mechanics of Bodies, Mechatronics and Biomechanics, the author of this work received three basic recommendations regarding measurement: 1) Do not measure! 2) If you measure, do not repeat the measurement!! 3) If you repeat the measurement, do not compare the measurements!!! However, this thesis boldly violates all three recommendations. In the introductory theoretical part, it briefly introduces the vibration of multi-degree of freedom damped systems and describes experimental ways of determining the modal damping. It also summarizes the Operational Modal Analysis (OMA) approach, explains the principle of the FDD method, and introduces EFDD (Enhanced Frequency Domain Decomposition) method which allows to determine not only natural frequencies and shapes as FDD does, but also modal damping of the shapes. A script in Matlab environment for processing vibrations using EFDD method is one of the thesis outputs. The script is first tested by computational model, where a model system with known damping is tested and damping is determined by the script. Subsequently, the work moves to the actual measurement of the real system - a bonded bar which is analysed by Experimental Modal Analysis and OMA, while the second variant uses commercial EFDD method (Brüel a Kjr company) and programmed script. In the conclusion of the thesis the damping results are compared to each other. The diploma thesis continues in Ing. M. Pop’s thesis – Modal Analysis Experimental Method Verification. From this work a part of measured data is taken. Specific cases of data use are always listed in the appropriate section of the text.
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The analysis of dynamic effects in the frog region of railway turnout
Balash, Arsen ; Pazdera, Luboš (referee) ; Smutný, Jaroslav (advisor)
This thesis is focused on measurement and analysis of dynamic effects on railway turnouts. Two same-type turnouts with different fastening elasticity were chosen. My attention was focused mainly on the crossing part of the turnout, where the highest dynamic impacts occur. The point of the thesis is comparison of the crossing part of turnouts in term of dynamic behaviour and assessment of influence of soft rail pads on spread of dynamic energy through the construction. A part of the thesis is choice of methodology of the measurement and proposal of convenient mathematical apparatus for analysing of the dynamic effects on crossings.
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Usage of transmission at electric vehicles
Běloušek, Ondřej ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
At first bachelor thesis divides different conceptions of electric vehicles with the aim to describe characteristic components which electric vehicles contain, and that make it different in comparison with conventional cars. From the principle of the electric vehicle it is obvious that electric energy which is necessary for electric drive must be stored and for this reason the batteries and important components are described. The next part is dedicated to the powertrain which is affected by the presence or absence of an internal combustion engine and its usage rate. Common feature is an electric machine which transforms electrical energy into mechanical energy, and which makes powertrain complete. Gearboxes used at electric vehicles are the next part which is affected by the type of power unit that they cooperate with. For that reason, one representative from each part is described. The representative of hybrid electric vehicles is planetary gear set of Toyota Prius 2010, representative of battery electric vehicles is one-speed transmission of Tesla cars and in the end the multi-speed transmission is mentioned because it is today´s trend. Because of the absence of an internal combustion engine for some types of electric vehicles, the noise and vibrations from gearbox come to the fore. The main source of the vibration is gears teeth contact and rattle of the other components. The last part of the thesis is focused on the design of a technical experiment that is suitable for measuring vibration and noise from two-speed automatic transmission. Firstly, the theoretical basis of measurement is described. The design itself takes into account the suitable measuring equipment, the right choice of components that realize closed loop and installation space of the acoustic chamber.
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Measurement of the vibrations
Diblík, Jan ; Kolouch, Jaromír (referee) ; Biolková, Viera (advisor)
Diploma thesis is focused on principles of measuring the vibrations using accelerometers and using them for making vibration measuring instrument with focus on modern integrated digital accelerometers. In the first part are described ways to measure acceleration and vibrations with available technical supplies with respecting place and purpose of measuring. In practical part are measured characteristics of used sensor, instrument for measuring vibrations is designed and built and for few experimental object vibrations or acceleration are measured and graphical interpreted.
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Simulation anlysis of turbocharger vibrations
Valo, Lukáš ; Lošák, Petr (referee) ; Březina, Lukáš (advisor)
The master thesis deals with computational modeling of a turbocharger vibrations and and assessment of influnce of passive dynamic vibration absorber on vibrations of actuator bracket. The use of dynamic vibration absorber was summarized in the research study. The analysis were performed using finite element method in ANSYS. Several computational models of turbocharger were created with different ways of modeling bolted joints between turbocharger parts. Modal analysis of each model was performed and the results were compared. For the selected model, the response to the kinematic excitation from the internal combustion engine for two load conditions was calculated using harmonic analysis. A simple model of vibration dynamic absorber was applied to the turbocharger model with reduced degrees of freedom and its influnce on vibrations of actuator bracket was investigated. Significant decrease of the maximum acceleration amplitude was achieved in a given frequency range when absorber parameters were optimized.
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Proposal of Measures to Reduce Noise of Roots Blower
Fučík, Ondřej ; Vacula, Jiří (referee) ; Novotný, Pavel (advisor)
The Master‘s thesis deals with issues of noise and vibrations of Roots blowers. In the theoretical part, potential sources of noise and vibrations are described. Detailed knowledge of basic types of mufflers is summarized, and their suitability for the corresponding application is evaluated. The practical part is focused on performing experimental measurements of the Roots blower’s noise and vibrations and the main sources of noise are determined. Subsequently, the existing anti-noise measures are analyzed and the proposal for adjusting the current measures for further noise reduction is presented.
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Virtual Prototypes of Drivelines
Janoušek, Michal ; Dundálek, Radim (referee) ; Slimařík,, Dušan (referee) ; Píštěk, Václav (advisor)
The thesis deals with computational modelling of heavy duty off-road vehicle driveline components. The thesis is divided to two main parts. The first part deals about modal analysis of selected driveline components. MBS computational study was performed based on modal analysis results. The second part of thesis deals with experimental verification of computational model. Pass-by noise and vibration measurement was performed. Measured signals were processed in frequency domain to find noise and vibration sources.
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Simulator of typical rotational machinery components faults
Vaľko, Matej ; Beneš, Petr (referee) ; Čala, Martin (advisor)
The objective of this thesis is to create a library in programming environment LabVIEW by company National Instruments, which objective is to simulate vibrations of different mechanical components, such as shaft, rolling element bearings, plain gearing and planetary gearbox in different circumstances and failures. The theoretical part contains information about typical failures of this mechanical components and their typical failure frequencies obtained from literature. In the description of theoretical part is inscripted simulator with user interface in already mentioned programming environment LabVIEW. Result of this thesis is library, which images time course of vibrations and spectral analysis for diffrent components with their respective failures.
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Monitoring of hydraulic machines using acoustic emissions
Závorka, Dalibor ; Pochylý, František (referee) ; Habán, Vladimír (advisor)
The goal of this diploma thesis is to clarify possibilities of usage of acoustic emission as a hydraulic machinery diagnostics tool. Especially for exposing presence of ruptures or cracks in the parts of machine, assuming changes in acoustic exposure of the part during operation. This clarification is based on series of simple measured experiments, which consist of monitoring the bolt placed in fluid stream inside of a pipe. This bolt was preloaded against inner wall of pipe by appropriate tightening torque. This preload is supposed to simulate effects of the size of rupture. High preload simulates small rupture or none in object and respectively small preload is supposed to simulate big rupture. A group of pressure sensors and accelerometers measures experiments and their evaluations are processed by script created in software MATLAB. Outputs of this script are charts with effective values of respective sensors from the entire record split into individual frequency spectrums. These charts compare spectrums of each configuration to judge effects of parameters changes.
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