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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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Vibrational analysis in time domain
Friedel, Petr ; Řehák, Kamil (referee) ; Dlugoš, Jozef (advisor)
The final thesis deals with the possibility of solving the problem of nonlinear vibration phenomena in the time domain using the finite element method. In the introductory part are presented possible simulation approaches for solving nonlinear vibration behaviour, areas of current use and the knowledge, which is needed for a real application using the explicit dynamics approach. In the next part is developed a methodology for investigating the frequency spectrum in time domain and its subsequent implementation on a simple nonlinear model. The third part of the thesis is focused on impact of the presence of nonlinear contacts applied on three-dimensional models and its effect at the frequency spectrum. The final part of the thesis includes the experimental measurement of the nonlinear spring vibration characteristics, in the resonance region and the subsequent replication of the investigated model for numerical FEM simulation. A final discussion of the results answers if experimental vibration measurement can be replaced by numerical simulation.
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Numerical simulation of gear mesh stiffness
Rackovský, Daniel Milan ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
The diploma thesis deals with the simulation of the spur gears mesh stiffness. The introductory part of the thesis presents a detailed review of the knowledge in the field of gear theory, gear error and also NVH of gears. The next part of the thesis describes the basic principles of the function of the parametric FEM model of gear mesh, which was developed for the purpose of this thesis. The last part of the thesis presents the results of FEM simulations in which the effect of manufacturing error of the gears on the STE waveform was investigated. The basis of the simplified production error model was the sine function. The effect of the number of periods of this function and the magnitude of the amplitude on the STE waveform was investigated. The effect of the magnitude of the load torque on the STE of the production-error gear was also verified. The magnitude of the amplitudes of the sine function was determined to match the allowable wheel shape tolerances according to ISO 1328-1. The problem was solved in Ansys Mechanical APDL using a parametric FEM model based on APDL language.
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A review study of metamaterial structures for applications in implantology
Tonhajzer, Michal ; Lošák, Petr (referee) ; Marcián, Petr (advisor)
This bachelor thesis deals with the influence of geometrical parameters variation on the stress-strain states and elastic characteristics of auxetic meta-materials. The research part of the thesis summarizes the basic properties of materials, methods of their determination, specifics in the response of auxetic meta-materials to external loads, occurrence and different types of auxetic structures. The next part of the thesis is devoted to the potential use of auxetic meta-biomaterials in implantology. In the computational part of the thesis, a parametric computational model of a particular auxetic meta-material structure was developed, on which a stress-strain analysis was subsequently performed and the influence of changing geometrical parameters on the material mechanical properties, stress and strain was assessed. Based on the results, two structures were created with parameter combinations chosen to eliminate undesirable effects while maintaining the desired properties. A detailed stress-strain analysis was performed on these two structures and the results were compared with a reference structure. Computational modelling was carried out using the finite element method in ANSYS Workbench 2023 R2.
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Design and analysis of reinforced concrete or masonry structures
Skočdopole, Jakub ; Švaříčková, Ivana (referee) ; Požár, Michal (advisor)
The bachelor's thesis deals with the static solution of the reinforced concrete ceiling slab and the inclined column of a 2-storey multi-storey building. The first part is devoted to the design of a point-supported plate, a cross-reinforced plate and an inclined column inclined by 15° from the vertical structure according to the limit state method. A spatial 3D model was created in the SCIA Engineer program, which was used to determine the internal forces in the structure. The correctness of the model results was verified by the sum of moments method. The second part deals with the study of the influence of the slope of the columns on the structure, when one row of columns in the 2nd floor was inclined and then the effect of this change on the structure and the static assessment were compared. Reference slopes chosen for the study: 0°; 15°; 30°; 50°, a partial spatial 3D model of the structure was created for each variant. The appendix of the bachelor's thesis is a detailed static calculation according to valid ČSN EN standards, drawing documentation and a study of the influence of the inclination of one row of columns on the reinforced concrete structure.
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Evaluation of stress and deformation of a bimetallic beam under changed temperature
Jurkovič, Vítězslav ; Horníková, Jana (referee) ; Burša, Jiří (advisor)
This bachelor’s thesis deals with stress-strain analysis of a selected bimetallic strip. First, a literature search is carried out on used bimetallic strips, including introduction of used materials and criteria for their selection. Next, an analytical calculation of free deformation of the strip at the chosen temperature is performed using rod assumptions. The following is a comparison with the results obtained using finite element method in the Ansys Workbench system. The analysis of the same strip with limited deformation is then performed using the finite element method. In this way, a stress analysis of the complete deformation constraint is performed first, including verification of the results using substitute of the deformation boundary by a force one. The following is a deformation analysis when the deformation is constrained by the selected valve spring with existing clearance, including the determination of the compression of spring. The outputs of this thesis are the results of the free deformation of strip at given temperature change, the analysis of the resulting stresses in strip due to the constrained deformation and the calculation of compression of valve spring at temperature changes.
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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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Engineering optimization of the pressing process of the turbo molecular pump rotor
Baklík, Jiří ; Čekán, Václav (referee) ; Vosynek, Petr (advisor)
This thesis deals with the issue of press fitted joints and the optimization of the rotor pressing process of the mechanical turbomolecular pump nEXT300T. The press fitted assembly consists of three main parts (blade discs, hollow shaft, main shaft). The blade discs are press-fitted onto the hollow shaft, then this assembly is press fitted onto the main shaft. The optimization was performed by computational modeling based on the finite element method, using ANSYS Mechanical 2024 R1. The pressing process has been optimized to reduce production costs. The assembling process is more expensive due to liquid nitrogen, which is currently used for cooling the press fitted parts. Design of the pressing temperatures was carried out. For heating a temperature of 130 °C was determined. For cooling a temperature of-65 °C was chosen, this can be achieved using an industrial freezer. Due to the change in pressing temperatures, tolerance fields of the components were designed to ensure that the assembly can be assembled and that the press joint will not be lost under operating load. For the connection between the blade discs and the hollow shaft, a radial interference of 0,0585-0,0695 mm is required for functionality. For the connection between the hollow shaft and the main shaft, a radial interference range of 0,01-0,02 mm is functional.
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Strength calculation of high-pressure steam piping according to EN 13480
Řezník, Dominik ; Pernica, Marek (referee) ; Létal, Tomáš (advisor)
The Master's thesis deals with the stress and strength calculation of a high-pressure steam piping system, which is part of the steam piping system of a waste-to-energy plant. In the theoretical part of the thesis, basic knowledge about stress and strength and piping systems (pipe support system, types of loads, fittings and other components) is summarized with respect to the used standards. Part of the theoretical section also includes one of the objectives of the thesis, which is to provide basic knowledge about the KKS codes. In the practical part, firstly, using the VVD software, the pipe class is calculated and created in order to design nominal thicknesses of all the pipes and fittings from the piping system. The core part of the work is the performance of the stress and strength calculation in the CAESAR II software, which includes the appropriate setting of the calculation model based on the calculated pipe class and the documentation from the customer, the selection of pipe supports and the adjustment of the pipelines based on the previous and ongoing results. As part of the calculation, the nozzle loads and support loads are also assessed and verified. In the last part of the work, a simplified FEM calculation of the dump-tube (transition component for steam discharge into the condenser) is performed in PRG NozzlePro software. All the modifications are continuously discussed and the results are then summarized.
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Influence of underground installation conditions on crack propagation in polypropylene pipes
Tesař, Jakub ; Gratza, Roman (referee) ; Hutař, Pavel (advisor)
The thesis addresses the issue of buried polymer pipes and the impact of installation conditions on their lifetime. Based on data obtained from standards, the values of external loads acting on the polymer pipe are determined. To apply these values in numerical calculations, the conversion of individual load components is also provided. Various stress values, simulating different burial installation conditions, are applied to a 2D model. The numerical calculation of the 2D model includes the progression of tangential stresses and their comparison with the standard. Furthermore, the influence of installation conditions on the burial depth of the pipe is analyzed. The comparison of models is conducted for both 2D and 3D models against the standard. The comparison verifies that the models are equivalent and closely correspond to the basic calculations according to the standard. The 3D model is then extended to include a crack, and the propagation through the pipe wall under the most critical load conditions is modeled. The concept of linear elastic fracture mechanics is used to estimate the lifetime of the pipe.
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