|
|
Tractor cabin skelet optimization
Saňák, Stanislav ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This thesis addresses the issue associated with the design of the tractor cabin frame. Agricultural machinery, including tractors, is utilized for work in highly challenging conditions such as fields or forest terrains, characterized by uneven, hilly, and often unpaved surfaces. Working in such extremely hazardous environments poses a significant challenge, especially for the operators of these machines. It is very common for drivers to lose control of the vehicle while navigating such terrain, resulting in the tractor tipping over on its side or roof, and in worse cases, experiencing repeated rollovers due to inertia. In such situations, the presence of a protective frame around the tractor cabin is the only possible means of crew rescue. However, the rollover of such a vehicle imposes extreme stress on the cabin frame due to the weight of the tractor and often its cargo. Historically, rollovers have been the leading cause of accidents resulting in fatalities of tractor crews, which prompted the establishment of standards aimed at reducing this type of accident. Tractors are tested against these critical situations to ensure the maximum possible crew safety. Nowadays, every manufactured tractor must comply with these tests. Since these tests are of a destructive nature, it is more cost-effective and time-efficient to first conduct tests using numerical simulations, within which the tractor cabin is optimized to successfully pass the given tests. The actual test is then performed on the final, already optimized cabin frame. In this study, a numerical simulation using the finite element method was conducted on the tractor cabin skeleton for the ROPS (Roll-Over Protective Structure) test, which simulates the tractor overturning. Based on the simulation results, optimizations were made to the cabin that were necessary to pass this test, which consists of several load cases. The optimized cabin frame was subsequently subjected to a basic dynamic analysis (modal analysis). This analysis identified the natural frequencies of the cabin that could be excited in the event of typical excitations acting on this structure (road surface irregularities, vibrations from the engine unit, and so on). Finally, based on real values obtained from experimental measurements, a harmonic analysis was performed. This analysis monitored the response of the frame to excitations corresponding to actual excitations from the engine unit.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
| |
|
|
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.
|
|
|
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.
|
guest ::
