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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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Analysis of the procedure for identifying potentially dangerous locations of weld joints in thin-walled metal structures during life assessment
Doležel, Daniel ; Pavlík, Ondřej (referee) ; Vosynek, Petr (advisor)
Hodnocení únavy svarů u tenkostěnných kovových konstrukcích je klíčové pro zajištění integrity navrhovaných konstrukcí. Navzdory zavedeným kritériím a S-N křivkám může být analýza životnosti svařovaných spojů u geometricky komplexních součástí značně komplikovaná. Hlavní překážkou je identifikace kritických míst z hlediska únavy pro detailní výpočet, což může být časově náročné i při využití metody konečných prvků (MKP). Tato práce podrobně zkoumá hodnocení únavy svarů, zahrnuje vhled do relevantní literatury, komerčních řešení a praktický kontext norem železničního průmyslu a směrnice FKM. Významným přínosem práce je vývoj automatizovaných FEMAP API programů pro MKP software Siemens FEMAP, které usnadňují proces analýzy. Tyto programy šetří čas a úsilí tím, že umožňují zjednodušenou analýzu založenou na konceptu lokálního nominálního napětí (local nominal stress) v souladu se směrnicí FKM. Metodika, podpořená vyvinutými programy, je v této práci popsána a prakticky demonstrována. Praktické přínosy této práce spočívají v poskytnutí alternativy ke komerčním softwarům, za účelem zvýšení efektivity analýzy životnosti svarů v kontextu konstukčních návrhů.
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Analysis of boundary conditions of biomechanical models of the lumbar spine
Kocián, Ondřej ; Kovář, Jaroslav (referee) ; Vosynek, Petr (advisor)
The bachelor thesis deals with a research study of biomechanical models of the lumbar spine. After a brief anatomical introduction, this thesis describes the process of building computational models for finite element analysis and what material properties of individual tissues are usually reported in the analyses. Subsequently, boundary conditions, i.e. more precisely, constraints and different types of loading and their influence on the model behaviour are described in order to provide the most accurate interpretation with respect to the actual behaviour of the lumbar spine. The most accurate method of loading the spine appears to be the introduction of a force flow through the instantaneous centres of rotation of each vertebra, based on a research study. In the last section, an experimental attempt is carried out on a computational model with a single loading force changing its location in order to better interpret the positions of the instantaneous centres of rotation. This method can sufficiently approximate the force states in the contact surfaces. However, it needs to be experimentally verified.
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Numerical modelling of residual stress in metallic materials
Rakušan, Jakub ; Vosynek, Petr (referee) ; Hutař, Pavel (advisor)
The presented master thesis is focused on residual stresses, more precisely on the implementation of residual stresses in simulations using the finite element method (FEM), experimental determination of residual stresses and the influence of residual stresses on fatigue crack propagation. In this thesis, the found approaches of implementing residual stresses in FEM are tested and the most suitable of the tested approaches is then used in the simulation experiment. By comparing the FEM simulation and experimentally measured data determined by the modified slotting method, the residual stress values on an induction hardened railway axle specimen are determined. This is followed by the verification of the determined residual stress values by X-ray diffraction and the determination of the effect of residual stress on the rate of propagation of long fatigue cracks.
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Analysis of hysteresis behavior of vertical headlight adjustment in an automobile
Holec, Radek ; Hadač, Ondřej (referee) ; Vosynek, Petr (advisor)
The thesis deals with the occurrence of mechanical hysteresis in the vertical adjustment mechanism of car headlights. The adjustment mechanism contains certain inaccuracies that can result in mechanical hysteresis, a phenomenon in which the light source does not return to its original position and the direction of the light rays is deviated from the intended direction. The first part of the paper deals with contacts and friction in the connectors in the Abaqus software. Then the development of the computational model is described. This model is further compared with the measured values of the actual headlamp. A DOE (Design of Experiment) was performed and these results were processed using regression and sensitivity analysis. The effect of clearances and high friction moments was found to be the most significant. The paper concludes by describing the principles by which hysteresis arises and quantifying the various parameters that affect hysteresis.
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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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Stress-strain analysis of the LKDS800 frame
Tománek, Jiří ; Vlk, Miloš (referee) ; Vosynek, Petr (advisor)
This diploma thesis deals with frame of the two-point crank press LKDS800, which was designed by company ŽĎAS a.s. Frame is welded construction creating the base of the press which has mass approximately 90 tonnes. Aim of this study was to perform strain-stress analysis of the frame. From obtained results perform optimization of mass this frame leading to reduce material costs and machining. In the process is frame loaded by nominal forces from the shearing process, under its own weight and inertia forces caused by moving components. As a result of the dynamic loading in welded joints there are risks of fatigue fracture. The manufacturer of the press is required to find the most loaded welded joint and it to assess the fatigue life.
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Finding kinematic quantities of a mechanism and a structural analysis of its members after blockage
Zvozil, Ondrej ; Vosynek, Petr (referee) ; Fuis, Vladimír (advisor)
Diplomová práca, ktorá vznikla v spolupráci so spoločnosťou AUFEER DESIGN (AFD), sa zaoberá analýzou konkrétneho stieračového mechanizmu automobilu. Najprv je uvedená stručná história stieračov. Stieracie sústavy sú potom rozdelené podľa ich usporiadania a spôsobu pohonu. V nasledujúcej kapitole je formulovaná problémová situácia, problém a systém podstatných veličín. Kinematické veličiny kľúčových bodov mechanizmu sú určené analytickým aj numerickým prístupom. Výpočtový model pre kinematickú analýzu je vyvinutý v Matlabe a SimMechanics. Ďalšia časť je venovaná vytváraniu konečno-prvkového modelu v programe ANSA. Všetky deformačne-napäťové analýzy sú vykonané v programe Abaqus. Prvá z nich je parametrická štúdia, ktorá odhaľuje kritické polohy mechanizmu z hľadiska tlakového namáhania určitých súčastí. Mechanizmus v kritických polohách je potom zaťažovaný so zablokovanými ramenami stieračov. Nakoniec sú urobené lineárne analýzy straty vzpernej stability súčastí, u ktorých môže nastať, nasledované nelineárnymi analýzami so zahrnutými imperfekciami.
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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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Application of finite element method to solve plane problems
Langer, David ; Vosynek, Petr (referee) ; Návrat, Tomáš (advisor)
The subject of this thesis is application of finite element method to solve planar problems of mechanical stress of machine components. The goal of the first part of the thesis is to provide the reader with an overview of commonly used FEM software and it's capabilities, both freeware and commercial solutions. Second part of the thesis deals with the usage of freeware for FEM calculations. The last part of the thesis consists of documentation to the FEM software created as a subject of this thesis. The documentation provides a detailed view of the selected type of calculation.
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