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Engineering optimization of a bolted joint under cyclic load
Pavlíček, Tomáš ; Kubík, Petr (referee) ; Vosynek, Petr (advisor)
This bachelor’s thesis deals with improving the service life of a cyclically stressed screw connection. In order to correctly determine the tension amplitude in the screw, it is necessary to know exactly the stiffness constant of the connection C. In this work, a comparison of analytical approaches for its calculation was made for a connection with a screw-in head screw. Based on a comparison with the numerical solution, it was evaluated as the most accurate approach according to the VDI 2230 standard. Furthermore, the influence of the size of the preload value on the life of the screw was assessed. It was found that the optimal value of the preload corresponds to the state when the clamping of the connected parts is lost. The last part of this work was focused on structural modifications that will improve the service life of the joint. The following design modifications were assessed: flexible screw, large area and spacer washer. The most significant increase in service life was achieved using a spacer washer.
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Analysis of the influence of the fixation setting of the fusion of the spinal vertebrae on the resulting correction of scoliosis
Kopecký, Tomáš ; Ščerba, Bořek (referee) ; Vosynek, Petr (advisor)
This bachelor's thesis deals with the numerical modeling of the spine with an established fixation device under three types of loading, with three types of connection between the last element of the fixator and its guiding rod. The thesis describes the creation of the spine and fixator models, as well as the setting of loading conditions. Three loading states are monitored, in both directions: flexion/extension, lateral bending in both directions, and axial rotation in both directions. Furthermore, the implementation of three types of connections for all these loadings is described. In the first case, the entire fixator is immovable, in the second case, the last element of the fixator can move along the axis of the spine, and in the last case, it can also rotate in all three directions. The evaluation and subsequent comparison of deformation in the direction of the spine axis are the outputs of this thesis. The final evaluation is that the displacement occurring is on the order of tenths of millimeters.
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Assessment of the strength of the lumbar spine fixator screw using stochastically entered input variables
Rapantová, Zuzana ; Hrabec, Pavel (referee) ; Vosynek, Petr (advisor)
The bachelor's thesis deals with the strength and fatigue of the spinal rod fixator. The topic is addressed by creating a computational model with two lengths of fixation screws. Simulations are performed using the Ansys software with the application of Six Sigma analysis. The strength analysis is quantified from the average load values, and the stress-strain analysis employs stochastic input variables. The results demonstrate that the modulus of elasticity of the cancellous bone significantly affects the deformation of the fixator. In the conclusion, the output data between the two lengths undergo statistical tests. Based on the acceptance of hypotheses regarding the equality of mean values, it is evaluated that a screw not passing through the entire cross-section of the cancellous bone in the vertebra is more suitable.
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Deformation analysis of the bearing of the main shaft of the wind power plant
Doležel, Miroslav ; Pokorný, Jan (referee) ; Vosynek, Petr (advisor)
This work studies a load distribution in spherical roller bearings of a main shaft in a wind power plant. The effect of the shaft and bearing houses as flexible bodies is considered for a particular geometry. The data are collected and processed by numerical computational modelling using the finite element method. Several complexity levels of models are studied. These analyses are also compared with the data obtained from the software Mesys. The results show that an inclusion of a flexible bearing housing has the greatest effect on the load distribution in the internal geometry of the bearing. The load distribution is also dependent on the direction of the radial load force. The most complex models are dependent on the friction coefficient in the internal bearing geometry, thus revealing the problem of interactions among the bearings. Knowledge of the load distribution contributes to the design of more reliable rolling bearings.
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Scanning and evaluation of a patient's hand with Dupuytren's contracture
Dalecký, Jan ; Vosynek, Petr (referee) ; Návrat, Tomáš (advisor)
This bachelor’s thesis deals with development of methodology for determining the angles between joints of the fingers of a patient with Dupyutren’s disease. The methodology works with 3D scan of the hand created with the help of a smartphone and rotating mechanism. Nowadays, the measurement is carried out with the help of a goniometer. However, this measurement is often inaccurate and may not be very pleasant for the patient. The main reason for the research is to improve the quality of the measurement results and evaluate the patient’s condition outside of the time spent in the clinic. An electronic database with the possibility of visual comparison of the patient’s conditions is also an advantage. The angle measurement process takes place on the computer in Fusion 360 and Blender software. Both measurement software and mobile scanning applications are selected to make this methodology as accessible as possible. All applications are freely accessible and user-friendly. The digitally measured values significantly match the real values and even give more relevant results for the evaluation of the severity of the patient’s condition.
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Strength analysis of the steering lever
Klimeš, Henrich ; Blokeš, Jan (referee) ; Vosynek, Petr (advisor)
The bachelor's thesis deals with the estimation of the number of cycles to failure of the steering lever material, which occurs on some Tatra vehicles. The theoretical part describes the necessary tools to calculate the control lever. In the second part, a simplified stress estimation is performed by using analytical calculation. The analytical calculation is then verified in the freely available program Salome Meca, in which the actual stress calculation on the 3D model of the steering lever takes place.
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Comparative analysis of light holder lifetime assessment methods
Holeta, Aleš ; Pokorný, Jan (referee) ; Vosynek, Petr (advisor)
This thesis addresses the topic of determining the fatigue life of a thin-walled holder fender and flashlight under variable loads. The aim of the thesis is to make a search study on the fatigue life of welded parts with respect to the thin-walled design of structures. The main objective is to evaluate the suitability of using different methods of fatigue life assessment on the holder fender and flashlight. The calculated fatigue lifetimes are confronted with experimentally obtained fatigue life-times. The fatigue lifetimes are determined by methods evaluating welded joints based on structural stresses and notch stresses. Finite element analysis was performed in the open-source programs Salome and Code_Aster. The modelling of the holder fender and flashlight geometry was performed at several levels. Based on the results, the most efficient method for the design of welded parts is the structural stress linearization method (also called “master S-N curve method”), which achieves comparable results to the effective notch stress method (considered as a reference), but with a multiply lower time consumption.
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Stress-strain analysis of the railway bridge in Zahrádky near Česká Lípa
Abdul moghni, Abdul rahman ; Vosynek, Petr (referee) ; Fuis, Vladimír (advisor)
Cílem této bakalářské práce je využití deformačně napěťové analýzy na Železniční most v Zahrádkách u České Lípy. Konstrukce mostu byla zjednodušena a vymodelována jako nosníková konstrukce. První část bakalářské práce byla věnována získávání vstupních dat a základních informacích z technické dokumentace mostu. V nosníkovém modelu bylo využito několik zjednodušení. První model považujeme za staticky neurčitý, zatímco druhý jako staticky určitou konstrukci. Každý model tedy obsahuje zátěž z důvodu vlastní váhy a zatížení způsobeno projíždějícím vlakem. Z důvodu objemnosti rovnic, využíváme k výpočtu software Maple. Zkontrolovali jsme i mezní stav vzpěru pro oba modely, avšak jsme uvažovali pouze zatížení vlastní váhou a zatížení způsobeno vlakem. Po získání analytických dat bylo důležité tyto výsledky ověřit. Toto bylo docíleno využitím metody konečných prvku za pomocí programu Ansys. Veškeré výpočty byly provedeny pro 2D modely. Jediná výjimka je numerická sekce, kde byl přidán 3D model za účelem porovnání s 2D modelem.
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Design of a new version of a trolley and docking station for channel racks
Pastrnková, Markéta ; Vepřek, Jiří (referee) ; Vosynek, Petr (advisor)
The master's thesis deals with the analysis of the current version of the trolley and the docking station of the channel racks and the design of modifications. The theoretical part describes the components of the storage channel system. There is also explained principle of pallet storage in this part. In the following chapter, several variants of the design of the lifting mechanism of the lifting platform are elaborated. The work also presents static structural analysis of the current version of the trolley and docking station, parametric study and topological optimization of one of the components. Static structural analyzes were partially solved in the finite element software RFEM by Dlubal Software s.r.o company, and mainly in the software ANSYS Workbench 2020 R2 by ANSYS, Inc. company.
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Analysis of mechanical loads of selected structural parts of the excavator during operation
Busta, Michal ; Maňas, Pavel (referee) ; Vosynek, Petr (advisor)
This thesis is focused on the issue of computational modeling of soil harvesting while using the compact excavator from the company DOOSAN BOBCAT EMEA s.r.o.. The solution consists in creating two computational models in Rocky DEM and Ansys Mechanical. Rocky DEM software is used to solve the disconnection of soil by excavator components using the discrete element method. The outcome includes courses of forces and moments during the particular time of the individual joints of the model that was used. The obtained courses are then applied as an external load to the joint of a selected structural part of the analyzed model using a kinematic model in ANSYS Mechanical. The kinematic model consists of simplified geometry models of individual parts of the excavator arm, and a more detailed geometry model of the analyzed part of the arm. All the parts are connected to each other by rotational bonds representing joints. A static structural analysis of the mechanical stress is performed in ANSYS Mechanical for the prepared model during the simulated process. Finally, the selected structural part is assessed with respect to the elastic limit and fatigue strength.
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