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Computational simulation of cross-roll leveling of rods
Benešovský, Marek ; Vrbka, Jan (referee) ; Petruška, Jindřich (advisor)
Final thesis describes two variants of computational models to simulate cross-roll leveling of rods, which are based on the Lagrangian approach to describe the continuum. Implementation of both variants was performed in ANSYS software, and their main difference lies in the choice of the type of elements for the discretization. An integral part of this thesis is the description of the principle, which is an evaluation of the curvature of the rod after completion of the simulation leveling. In the other part of the work are presented the results, which are then compared with realized experiment and simulation algorithm for cross-roll leveling based on the Euler approach. The final part is dedicated to the optimal settings of the leveller.
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Space mission design
Koziel, David ; Navrátil, Jan (referee) ; Zikmund, Pavel (advisor)
In this work, there are basic laws and knowledge relating to space flights into an orbit around the Earth. Also, there are instructions for beginners, who want to work with the GMAT program (General Mission Analysis Tool), which is the program used for designing space missions. In the final part of the work, there is also a use of the program demonstrated on a specific mission of a satellite (CubeSat) into the Geostationary Earth Orbit. In this section, there is a described method of work, individual relevant functions of the program and possibilities, and a way of work in it. Finally, graphical and data outputs of the simulation are evaluated. Therefore, the output of the work is complex characteristics of the basics of problems of space mission design and a brief GMAT software guide, which could be used in the future to teach.
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Influence of process parameters in forward extrusion on the die loading
Pokorná, Jana ; Návrat, Tomáš (referee) ; Petruška, Jindřich (advisor)
One of the decisive factors of effective using of forward extrusion technology is lifetime of forming tools. Die is very loaded forming tool which loading and therewith related lifetime can be significantly affected by its construction. Construction also affected quality of extruded material. Finete element method allows to simulate this process and assess force which is needed to extrusion and state of stress in die and extruded material. Numerical simulation was realized in program ANSYS 11.0. Influence of reduction, angle of reduction, lenght of extruded material, rounding transition of die parts, extruded material and friction coefficient on die loading and emergence of cracks in extruded material was set in this diploma thesis. Results can be used to die construction optimalization.
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Comprehesive Theoeretical Analysis of Ring-Core Method for Residual Stress Determination
Civín, Adam ; Holý, Stanislav (referee) ; Plánička, František (referee) ; Frydrýšek,, Karel (referee) ; Vlk, Miloš (advisor)
Comprehensive analysis of the ringcore method used for the determination of the residual stresses in mechanical components is presented in this thesis. Principles, advantages, disadvantages and applicability of this semidestructive experimental method are discussed too. At the same time the ringcore method is compared with the hole drilling method, which is used more frequently. All aspects of the ringcore method are analyzed by the finite element method. FE simulations, performed on the universal numerical model, verified principles of the integral method and the incremental strain method. FE simulations also provided basic information for the uncertainty analysis, which significantly affects the accuracy of the residual stress measurement. The main goal, which the present work deals with, is to create a global overview of all ringcore methods´ aspects elaborated in a clear and complex form.
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Computational simulation of leveling of non-circular rods
Stráník, Radim ; Návrat, Tomáš (referee) ; Petruška, Jindřich (advisor)
This bachelor’s thesis illustrates the principle of straightening rolled through long table roll straightening machines using repeated plastic deformation, based on Eulerian description of the material flow. Thesis describes the program on computational simulation process straightening rods and extends it an easy to use input module for entering non-circular cross-section rods. At the end of the discussion also introduces the optimal settings for all input parameters to achieve best results.
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Optimization of Modal Damping of Blades in High Pressure Stages of Steam Turbine
Lošák, Petr ; Zeman,, Vladimír (referee) ; Pešek, Luděk (referee) ; Kellner,, Josef (referee) ; Malenovský, Eduard (advisor)
Steam turbine rotor is a very complicated assembly, typically consists of several rotor rows. Due to design limitations and increasing demands on the efficiency of the steam turbines, it is practically impossible to avoid all of the resonant states. The significant vibrations can occur, for example, due to passing resonance state during turbine start up or run out. In the worst case the turbine operates state is close to the resonance state of the rotor row. This leads to the significant oscillation of the bladed disk, and may results in the blade (or blade to disk joints) high cycle fatigue. These parts are highly loaded components and any cracks are unacceptable. Therefore it is absolutely necessary to damp vibration by using, for example, passive damping elements. The damping element analyzed in this thesis is a strap with an isosceles trapezoidal cross section, which is placed in the circumferential dovetail groove in the blade segmental shrouding. The sliding between the contact surfaces leads to the dissipation of energy which causes decreasing of undesirable vibrations. The main aim is to design the optimal dimensions of the strap cross-section with a view to the most effective damping of vibration for a particular turbine operating state. Considered bladed disk has 54 blades which are coupled in 18 packets by segmental shrouding. The damping element is paced in circumferential dovetail groove created in the shrouding. This type of damping element is suitable especially for damping vibrations in the axial direction and only with the mode shape with the nodal diameters. The modal properties of the bladed disk are influenced by the sliding distance. Since the friction force depends on centrifugal force acting on the damping element and on the angle of the side walls of the strap and groove, the sliding distance can be influenced by the damping element dimensions. During the optimization process the best possible size of middle width, height and angle of damping element cross-section is searched. The strap weight, contact area size and flexural stiffness of damping element can be influenced by these parameters. Their change has also impact on the size of the contact pressure and thus on the size of relative motion as well. As stated previously, the damping efficiency is influenced by the relative motion between the damping element and shrouding. Numerical simulation in time domain is very time-consuming, especially for systems containing nonlinearities. In order to verify dynamic behavior of the computational model with the passive friction element in numerical simulations, the simplified model is created. The model is created in the ANSYS environment. The main requirement imposed on this model is to have as small number of degrees of freedom as possible, so the time needed to perform the simulation is reduced to a minimum. To satisfy this requirement the simplified model is a cantilever beam with rectangular cross section. The dovetail groove is created in this model in longitudinal direction. In this groove is damping element. In addition to damping element dimensions optimization, the influence of each design variable on model dynamic behavior is studied. The results are verified experimentally. Experiment also shows other interesting results that confirm the damping element influence on the modal characteristics. The gained knowledge is used to optimize the dimensions of the damping element in the model of the bladed disk.
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Space mission design
Koziel, David ; Navrátil, Jan (referee) ; Zikmund, Pavel (advisor)
In this work, there are basic laws and knowledge relating to space flights into an orbit around the Earth. Also, there are instructions for beginners, who want to work with the GMAT program (General Mission Analysis Tool), which is the program used for designing space missions. In the final part of the work, there is also a use of the program demonstrated on a specific mission of a satellite (CubeSat) into the Geostationary Earth Orbit. In this section, there is a described method of work, individual relevant functions of the program and possibilities, and a way of work in it. Finally, graphical and data outputs of the simulation are evaluated. Therefore, the output of the work is complex characteristics of the basics of problems of space mission design and a brief GMAT software guide, which could be used in the future to teach.
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Comprehesive Theoeretical Analysis of Ring-Core Method for Residual Stress Determination
Civín, Adam ; Vlk, Miloš (advisor)
Comprehensive analysis of the ringcore method used for the determination of the residual stresses in mechanical components is presented in this thesis. Principles, advantages, disadvantages and applicability of this semidestructive experimental method are discussed too. At the same time the ringcore method is compared with the hole drilling method, which is used more frequently. All aspects of the ringcore method are analyzed by the finite element method. FE simulations, performed on the universal numerical model, verified principles of the integral method and the incremental strain method. FE simulations also provided basic information for the uncertainty analysis, which significantly affects the accuracy of the residual stress measurement. The main goal, which the present work deals with, is to create a global overview of all ringcore methods´ aspects elaborated in a clear and complex form.
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Comprehesive Theoeretical Analysis of Ring-Core Method for Residual Stress Determination
Civín, Adam ; Holý, Stanislav (referee) ; Plánička, František (referee) ; Frydrýšek,, Karel (referee) ; Vlk, Miloš (advisor)
Comprehensive analysis of the ringcore method used for the determination of the residual stresses in mechanical components is presented in this thesis. Principles, advantages, disadvantages and applicability of this semidestructive experimental method are discussed too. At the same time the ringcore method is compared with the hole drilling method, which is used more frequently. All aspects of the ringcore method are analyzed by the finite element method. FE simulations, performed on the universal numerical model, verified principles of the integral method and the incremental strain method. FE simulations also provided basic information for the uncertainty analysis, which significantly affects the accuracy of the residual stress measurement. The main goal, which the present work deals with, is to create a global overview of all ringcore methods´ aspects elaborated in a clear and complex form.
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