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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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Design apparatus for measuring geometric accuracy of machine tools
Holcman, David ; Marek, Tomáš (referee) ; Holub, Michal (advisor)
This bachelor’s work deals with modern methods of geometric accuracy measurement of machine tools, modal analysis and definition of demands on used agents during the measurement process. A part of this work is dedicated to description of numerical finite element method, which is the cornerstone of ascertaining the natural frequencies by a software program. In the closing part the appropriate adjustments of minimisation of influence on measurement are suggested.
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Modal analysis of vocal folds models with descrete parameters
Lekeš, Filip ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
Bachelor’s thesis deals with modal analysis of computed models of human vocal folds. It’s about finite element and analytical model where values first eigenfrequencies come under male vocal folds. Research part applies to biomechanics of vocal the human voice, which is followed by an overview of computational models. Finite element model is completely created and solved by ANSYS Workbench commercial program, which uses the finite element method to simulate a problem. Solution of analytical model uses freely available Python programming language. Analysis of the results and comparison of approaches belong to main objectives of the presented work. The proposed analytical model can serve future students for detailed understanding of human vocal oscillations.
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Dynamic analysis of structure loaded seismic loads
Šulerová, Zdeňka ; Nevařil, Aleš (referee) ; Vlk, Zbyněk (advisor)
This thesis deals with the calculation of response of reinforced concrete construction on the effect of seismic tension. Time and spectral analysis were made. They are mentioned as possible ways of calculation in EN 1998 - 1:2004 norm. Final figures of global deformations and stress on selected beam from the time and spectral analysis were firstly compared for the horizontal components of seismic stress affecting only in one direction. Subsequently comparison of time progress to combination of these effects mentioned in relevant norm was made. In the conclusion the results of used analysis are appraised.
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Influence of Glottal Shape of Human Vocal Fold on its Modal Characteristics
Zelinka, Martin ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
The main goal of the bachelor thesis is to create a parametric model with a variable angle of the human vocal fold and to determine the first two frequencies of vocal fold oscillations for all angles from -40 ° to + 40 °. The result is supported by a review of the anatomy of the human vocal system, the creation and modification of the voice, and current models of the human vocal fold. The model used for this work is created in the 3D CAD Inventor model software. Modal analysis is solved in the computer program ANSYS Workbench, solved using finite element methods.
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Drivetrain of a 8x8 truck
Hebnar, Tomáš ; Kučera, Pavel (referee) ; Píštěk, Václav (advisor)
This thesis is focused on building a replacement torsion system of drivetrain of 8x8 and 8x4 trucks and subsequent computational analyses of built systems. There were made two analyses. The first one is a computational analysis of the shapes of vibration and The second one is a sensitivity analysis. The sensitivity analysis is studying effect on the size of the natural frequencies under the effect of gear ratio.
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Animation of the stress-strain behaviour of helical springs
Gabriel, Tomáš ; Klapka, Milan (referee) ; Hartl, Martin (advisor)
This thesis is dedicated to the creation of educational animations depicting issues with the design of helical springs. Thesis contains collection of the necessary materials, describes the animating process and presents the final results. Main topics of the work are the stress across a cross-section of a loaded spring, fatigue and natural frequency of an oscillating spring.
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Using of Transfer Matrix Method for Modal Characteristics of Vocal Tract
Meisner, Patrik ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
The first part of the bachelor thesis describes anatomy of the vocal tract, voice creation and its modification. Some pathologies are listed at the end of the first part. The contents of second part are previously published computational models of the vocal tract followed by the method of transfer matrices for the Czech vowel [u:]. Modal analysis is performed by the transfer matrix method. The output are first three natural frequencies. Obtained frequencies are compared to values in the literature and to values calculated by the finite element method.
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