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Stability analysis of swinging props turbines
Bukovský, Petr ; Navrátil, Petr (referee) ; Skalka, Petr (advisor)
Master thesis deals with a computing simulation of two props turbines lines. The thesis output is gaining maximum possible load, at which a commencement of deformation stability critical state for various geometrical imperfections has not arisen yet. The calculation has been done by FEM in two different ways: linear solution (using a calculation conversion into eigenbuckling) and nonlinear solution (using a FEM deformation option). Result analysis compares both methods outcomes. Safety factor for the props operation has been proposed taking into consideration known influences on operating state.
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Modelling and analysis of auxetic materials response on the mechanical loading
Vítek, Tomáš ; Skalka, Petr (referee) ; Ševeček, Oldřich (advisor)
This bachelor’s thesis is focused on auxetic materials, especially on their response on the mechanical loading. Historical development, significant mechanical properties, different ways of modelling and possible practical applications of these materials are described in the research part of the thesis. The computational part deals with the detailed analysis of selected auxetic structures in order to evaluate their elastic properties depending on different geometric parameters and also on the magnitude of applied deformation. Computational modelling is primarily performed using the software ANSYS Mechanical APDL based on the finite element method (FEM). This method is briefly explained in one chapter. In the following part of the thesis the process of creating a parametric model and reducing the whole structure to a minimum geometry size (a part of a basic unit) is described. A detailed explanation of generating the mesh and setting appropriate boundary conditions is also included together with the results evaluation. Elastic properties obtained by numerical simulations are then compared to available analytical model. Dependencies of elastic properties are presented for a wide range of values of selected geometric parameters and applied deformations of the structure considering small and large deformation regimes. An influence of these parameters on a structure response during the mechanical loading is discussed based on these dependencies. At the end of the thesis the values of elastic properties computed using a finite element method are confronted to the experimental data available in the literature and the validity of the computational model is considered based on this comparison.
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Homogenization of open foam structures using Kelvin cell
Barančík, Milan ; Navrátil, Petr (referee) ; Skalka, Petr (advisor)
The bachelor thesis deals with homogenization of open foam structures using Kelvin cell. A computational model of the foam structure was created and converted into a computational model of solid with corresponding material characteristics in ANSYS software. Subsequently, a parametric study of the effect of Kelvin cell proportions on solid material characteristics was done. The output of the study was a generalization of the dependence of solid material characteristics on Kelvin cell proportions. Lastly, the suitability of the generalization was verified and achievements were evaluated.
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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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Napjatostně deformační analýza rozhledny Hraniční vrch
Novák, Tomáš ; Skalka, Petr (referee) ; Fuis, Vladimír (advisor)
Bachelor thesis is focused on stress and deformation analysis of strut frame, which is based on lookout tower Hraniční vrch by the city Město Albrechtice. The main goal is to create simplified 3D model and his resulting analysis at various degree of static indeterminateness. The first part contains introduction to history of lookout tower, theoretical introduction to bar, strut frame and limit state, followed by calculation of three various static indeterminate level. In the last part is verification of analytic results by numeric method. Another goal is to create thesis, which will also give a guidence for future solver of more complex 3D strut frame.
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Influence of Kármán vortices on the body in the air flow
Matějka, Jan ; Pochylý, František (referee) ; Skalka, Petr (advisor)
In master thesis there is main model object a 100 m high steel chimney located in the area of paper mill near the town of Świecie in Poland. In the past there was an accident with the failure of this particular construction. There is analyzed an effect of Kármán vortices on deformation – stress response of this chimney. The effect of Kármán vortices on the body in the air flow is considered to be cause of the accident in this case. In master thesis is investigated an opportunity to minimize these effects on body in the air flow (In this case the body is the above mentioned steel chimney). The negative effects termination (like for example minimalization of range of excitation frequencies or minimalization of drag forces acting on the chimney) is carried out by use of aerodynamic protection shell.
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Stress-strain analysis of clamping mechanism element
Gergeľ, Erik ; Navrátil, Petr (referee) ; Skalka, Petr (advisor)
The bachelor thesis deals with creation of computational model and solves Stressstrain analysis of a car window clamping mechanism element. The main focus of thesis is to locate a critical area of part and find out the distribution of stress is this area. FEA system ANSYS was used for this analysis. The shape optimization based on results of FEA was successful. The equivalent stress was significantly lowered. It would be able to increase the operating time of clamping element.
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Optimization of dimensions of the base frame to form for large castings
Mottl, Jan ; Navrátil, Petr (referee) ; Skalka, Petr (advisor)
In this thesis the problem of optimizing the dimensions of the base frame molds for casts with FEM and for 4 weight classes, ie casts weighting 1, 3, 5 and 10 tons is solved. For the evaluation of the FEM ANSYS program was used. There are gradually presented optimization procedures for all four weight classes. There was established the persistence of forms and frame and at the end the conclusion of the technical-economic evaluation of the proposed forms in terms of material savings in comparison to the current state of production was made.
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Sheet thickness optimization of the bolted steel tank
Konečný, Jiří ; Lyčka, Petr (referee) ; Skalka, Petr (advisor)
This thesis deals with bolted steel tanks, especially modification one of them. This modification is realized in cooperation with Kohimex spol. s r.o., which is assembling theese tanks for many years. The thesis continues on the bachelor one called "ASSEMBLED STEEL TANKS", which has already dealt with this issue. At the beginning of the thesis the issue of tanks is explained. Furthermore, there is made description of the tank modification details. At the next stage, the work presents stress-strain states of the tank, first for the current tank and then for the modified option. On the basis of completed analysis is made economic evaluation of design modified tank option due to the current tank. The results of this study allow better issue understanding of bolted tanks designing or they give impuls to improve the current way of designing.
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Determination of mechanical properties of open ceramic foam structure using finite element method
Barančík, Milan ; Navrátil, Petr (referee) ; Skalka, Petr (advisor)
The thesis is concerned with creating of a computational model of open-cell ceramic foam and determining mechanical properties of open-cell ceramic foam using computational modeling. The geometry of Kelvin cell was used for creating the model of geometry of the foam. The model of geometry of ceramic foam structure was meshed with solid elements, with beam elements and with combination of rigid beam and beam elements. Elastic properties of the foam were determined by two types of mechanical loading. Young´s modulus and Poisson´s ratio were determined by tensile/compressive mechanical loading and shear modulus was determined by shear mechanical loading. The relationship between mechanical properties of the foam and the ratio of diameter of strut D and length of strut L was analysed in the thesis. A good agreement was found out between Young´s modulus determined by solid element based and Young´s modulus determined by modified beam based model of geometry of the foam structure – for ratio D/L up to 0,6. In the case of Poisson´s ratio a good agreement was determined up to D/L = 0,4. In conclusion the value of Young´s modulus 1,97 GPa which was determined by computational modeling was compared with the value 1,56 GPa which was determined experimentally on ceramic foam. This difference was caused by idealization of geometry of the real ceramic foam material. In addition, mechanical properties of the ceramic foam material are influenced by structural imperfections of the material.
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