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Analysis of Modal Shapes and Natural Frequencies of Real-Shaped Vocal Fold
Horčic, Václav ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
This bachelor's thesis deals with the modal analysis of a model based on a 3D scan of the human vocal cords. This is a model solved by the finite element method, where the value of the first natural frequency roughly corresponds to the value of the fundamental frequency of female vocal folds. The research part of the thesis is devoted to an overview of finite element models of the geometry of the vocal cords, which is followed by a brief description of the anatomy and physiology of the human speech system together with the theory of the formation of the human voice. The finite element model is created using a 3D scan of the vocal folds in the commercial program ANSYS Workbench, in which it is solved by the finite element method.
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Design and production of pendulum tuned mass damper
Čupr, Michal ; Rubeš, Ondřej (referee) ; Kšica, Filip (advisor)
In a real environment, various external conditions can cause vibration of the machines, buildings or other systems. To prevent vibration of the system with low frequencies, pendulum tuned mass damper can be installed. The first part of this thesis describes the oscillation of simple structures for systems with one or two degrees of freedom. This analysis is then applied to mechanism that contains pendulum tuned mass damper. The damper’s principle is explained along with its important parameters and properties. Design and tuning of the damper are explained. Text continues with description of several types of the damper and there are mentioned some examples of their applications. In the final part, a model of the mechanism with pendulum tuned mass damper is designed and it is described mathematically using programs Matlab and Ansys. Subsequently, the model was made and the real model was compared with mathematical model. It was found that effectiveness of the damper depends most on the natural frequency of the system and the dissipation energy from it. The manufactured pendulum damper effectively dampens the oscillation of the real model, and the course of its oscillations corresponds to the mathematical model.
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Modal Analysis of the Classical Guitar Bridge
Ondečko, Adam ; Votava, Tomáš (referee) ; Hájek, Petr (advisor)
The bachelor thesis deals with the determination of the natural freqvencies and mode shapes of a classical guitar bridge and their influence on the function of the guitar. The function of the guitar is described by the oscillations of the individual oscillators: the strings, the air in the cavity of the guitar, the top and bottom plates, and then by their oscilation as a system. In the bachelor's thesis the roles of the guitar bridge are discussed and the different types of guitar bridges are presented. In the thesis, the guitar bridge is considered as a separate component and as part of the guitar's top plate. The mode shapes and natural freqvencies are obtained using modal analysis with the use of computational modelling using the finite element method. The natural freqvencies are determined for 2 types of guitar bridges, the effect of the guitar bridge on the mode shapes and natural freqvencies of the guitar top plate is further evaluated. The natural freqvencies of the classical guitar bridge affect the tone quality and the duration of oscilation of the string. Tones close to the natural freqvencies of the guitar bridge sound louder and last shorter amount of time than the others. The guitar bridge changes the stiffness of the top plate and thus influences its mode shapes and freqvencies.
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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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Analysis of dynamic properties of pneumatic actuator
Hrivňák, Ján ; Žatko, Miroslav (referee) ; Malenovský, Eduard (advisor)
This thesis deas with dynamic analysis of pneumatic actuator which is used as regulation mechanis of turbochargers with Variable Nozzle Turbine (VNT) technology. The first part of work is focused on experimental modeling which goal is obtaining Frequency Response Function on specify frequency range by Frequency Response Function Analysis – FRFA. Dominant vibrations of pneumatic actuator active parts is expected on this specify frequency range. Results of experimental modeling will be used for gaining input parameters for numerical computation as well. The second part deal with Pre-Stressed Modal Analysis and subsequently Harmonic analysis. Obtained results with numerical and experimental analysis will be compared. This part of diploma thesis is solved in programmatic environment ANSYS Workbench.
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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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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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