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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.
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Reduction of vibration and noise at passenger car interior
Patočka, Pavel ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This thesis addresses the issue of reducing vibrations and noise in the interiors of passenger vehicles, which is commonly tackled today by additional soundproofing using vibration-damping and sound-absorbing materials. In the research part of this thesis, besides methods for measuring vibrations and noise, the properties and application methods of these materials are described in detail. As the name of these materials suggests, their main goal is to dampen vibrations and absorb sound. Their principle, in simple terms, consists of converting mechanical or sound energy into another form of energy (most commonly thermal energy). However, the application of these materials to a structure affects its modal properties, including natural frequencies and mode shapes. To further investigate the influence on natural frequencies and mode shapes after applying vibration-damping material to a structure, both numerical and experimental modal and harmonic analyses of a simple metal sheet sample were conducted. The benefits of vibration-damping and sound-absorbing materials in terms of additional vehicle soundproofing were evaluated based on a road test conducted under real operating conditions.
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Harmonic Analysis of the Double Bass Bridge
Čalkovský, Lukáš ; Votava, Tomáš (referee) ; Hájek, Petr (advisor)
This bachelor's thesis focuses on the research of string instruments and their mechanical properties. It explores the double bass bridge and its importance. On a model created in the SolidWorks program, modal analysis was performed using the ANSYS software, which determined the frequencies and shapes of the individual modes. Harmonic analysis was also performed and analysed. Part of the investigation was to analyze the possible cause of the formation of so-called wolf tones. The double bass bridge does not exhibit any special characteristics in the double bass range, so it is not the cause of this anomaly.
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Suspension footbridge across the Elbe River
Gregor, Petr ; Kocourek, Petr (referee) ; Stráský, Jiří (advisor)
The objective of this master´s thesis is a design of suspension footbridge across the Elbe river. The footbridge is suspended construction by three spans. The brick deck is supported on the outer edges and it is kept in a parabolic arc. The suspension cables are kept at two inclined levels. The model is implemented in the program ANSYS. The solution is non-linear. The designe is according to the europien standart.
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NVH parameters determination of gearbox housing
Belák, Kristián ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This master’s thesis deals with determination of NVH parameters of the gearbox housing. Introductory part is focused on the necessary theoretical knowledge. Subsequently, it contains the modal analysis with the computational and experimental approach, which are being compared to each other. In the case of the computational approach, analysis of the influence of bolt pretension on the modal properties is also involved. The thesis continues with the harmonic analysis with the computational and experimental approach, including their mutual comparison. Based on these analyses, design modifications for improvement of the NVH parameters are designed at the end of the thesis, which are being compared to each other and to the original geometry, using the computational approach.
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Design of modern speaker body with usage of new technology
Kůst, Martin ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This diploma thesis deals with the analysis and design optimization of a speaker cabinet (enclosure) produced by the additive technology of 3D sand printing. The introductory part is devoted to the theory, both in the field of noise, vibration and the method of their calculations, as well as the theory of speakers and their systems. Numerical and experimental modal analysis is performed, which were compared to determine the mechanical properties of the new material, including material damping. This is followed by experimental and numerical harmonic analysis, with output in the form of a numerical model describing the behaviour of the structure during its excitation. The data are compared with a modal analysis of the internal acoustic space and the critical shapes and their frequencies are determined. At the end of the work, construction modifications are proposed to increase the rigidity of enclosures, the influence of which is evaluated on the created numerical models.
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Optimization of modal properties of the body in the air flow
Matějka, Jan ; Švancara, Pavel (referee) ; Skalka, Petr (advisor)
The bachelor thesis deals with dynamic analysis of the rod body, which is excited by the Karmán vortices. In this thesis a method of countermeasure is also verified, which could be possibly used in order to supress the state of resonance in the body and which could minimalize the influence of the Karmán vortices on the structure. This method consists in change of the mass in specific parts of the body in order to change modal properties of this body. The main goal of the thesis is to find suitable configurations of the mass distribution depending on air flow velocity for purpose of minimalization the influence of the Karmán vortices on the construction. This is achieved by optimization of modal properties. The optimization is based on results of harmonic analysis and is considering possibility of practical use.
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Vibration Propagation Analysis of Coupled Structure Acoustic Space
Kostelník, Jan ; Pellant, Karel (referee) ; Novotný, Pavel (advisor)
The aim of this Master’s thesis Vibration Propagation Analysis of Coupled Structure Acoustic Space is to analyze vibration propagation in combustion engine, from combustion space through solid structure to fluid surroundings. Then analyze the noise increase as pressure changing in fluid space around the solid structure. There was made a analyze of single piston engine in different frequency and piston location. A simulation of distribution of a pressure waves was made in an ANSYS application.
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Design of Data Acquisition Equipment IMC Fastening System in the Car
Černý, Martin ; Jeník, Radomír (referee) ; Ramík, Pavel (advisor)
Devices for measuring the dynamic load and vibration of certain parts of the bodywork or parts of other parts of the vehicle are made using accelerometers and measuring instruments IMC. It must be simply installed into the interior of the vehicle so that it is not necessary to remove any parts of the interior and to avoid damage to all parts of the interior. The preparation must also withstand the considerable dynamic load generated by the harder operation tests.
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Analysis of the effect of damping on the magnitude of the response during dynamic headlamp excitation
Lukáš, Jan ; Biskup, Martin (referee) ; Vosynek, Petr (advisor)
The aim of the submitted diploma thesis is the magnitude determination of the headlamp response to the dynamic excitation. Currently it is necessary to measure this response, because it is one of the assessed criteria of quality of the headlamp. When comparing results of the experimental measurement and the computational modelling, a good consensus of resonant frequencies is observed, but there are significant differences in acceleration amplitudes. The cause of this is the variable damping value. The theoretical part of the thesis deals with polymeric materials, basics of oscillation and damping. It serves to understand the mechanisms, which influence the results of the experimental measurement. The practical part is dedicated to the procedure of the computational modelling and the experimental measurement implementation. The analysis of the experimental measurement results leads to an ascertainment of nonlinearities, which influence the headlamp behaviour. The results of a sensitivity analysis of the computational modelling are used to create curves, on the basis of which the damping is estimated. The inclusion of the estimated damping into computational modelling leads to reduction of the compared differences of the acceleration amplitudes. The conclusion of the thesis contains the recommendation for the damping determination during the computational modelling of the headlamp.
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