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Analysis of the three-dimensional shape of the crack in the cantilever beam
Ozimák, Eduard ; Ševeček, Oldřich (referee) ; Majer, Zdeněk (advisor)
The bachelor thesis deals with the numerical calculation of the stress intensity factor using the finite element method and the subsequent modelling of the crack face shape on a simple beam in the ANSYS Mechanical APDL computational environment. In the introductory part of the thesis, the history and beginnings of fracture mechanics are described. Then, the basic theoretical knowledge and relationships needed when working with a body containing a crack are described. This is followed by an introduction to the finite element method. In the second part of the bachelor thesis, the procedure of performing numerical calculations and modelling in the ANSYS environment is described in detail.
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Modelling of the randomly formed ceramic foam structure for FEM simulations
Papšík, Roman ; Navrátil, Petr (referee) ; Ševeček, Oldřich (advisor)
This bachelor thesis deals with construction of ceramic foam model with various levels of (ir)regularity for finite element simulations in Ansys. The main objective is to substitute the complex structure of the open cell foam using the beam elements, enabling to perform FE analysis on much larger volumes of foams than the realistic foam models composed of solid elements. In this work, the technique of the model creation is based on the Voronoi tessellation and enables choice of arbitrary (ir)regularity of the modelled structure. The created source codes generate the model data directly in the syntax of APDL language for FEM system Ansys. The first part of the work describes several methods of the space partitioning and methods for substitution of the real foam structure by simplified “wire” model. The second part defines the Voronoi tessellation (diagram) as a key technique for creation of the foam model and describes its algorithms. The next part of the work deals with possibilities and utilizations of various software and libraries, describes creation of the own code in mathematical software Matlab and way how to transfer the model data into the system Ansys. The last part of the work demonstrates functionality of the created model on several FEM simulations, studying response of the ceramic foam on the external mechanical loading, upon consideration of various levels of the foam structure irregularity.
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Modelling and analysis of the contact failure of ceramic materials
Machů, Zdeněk ; Majer, Zdeněk (referee) ; Ševeček, Oldřich (advisor)
This bachelor thesis deals with contact damage of ceramic materials. The purpose of this work is to create an analytical and FEM model of contact between a sphere and flat plate and subsequently use these models to analyse loading conditions that lead to crack initiation in the ceramic plate. The research part contains description of contact failures in ceramic materials with strong emphasis on Hertzian cone crack, followed by Hertzian theory of contact between two spheres and Hertzian stress field equations for flat plate. The next part of research chapters describes how contact problems are modelled in FEM software ANSYS Mechanical APDL and introduces the basics of fracture mechanics, which are necessary for the prediction of ring crack initiation. The next chapter contains information about the creation of analytical and FEM model and includes illustrative results of both models, which are then compared between these two models. The last chapter of this work deals with fracture mechanics FEM model that can simulate the ring crack initiation. This chapter also contains analysis of ideal crack position, where the crack has the best conditions for its initiation and growth. The last part of this chapter contains parametrical study where critical loading conditions are analysed in relation to radius of indentation sphere and different mechanical properties of used ceramic plate. In the final part of this work, the results of fracture mechanics FEM model are compared to experimental results of real specimens.
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Micro-cellular impact absorbers
Rakušan, Jakub ; Ševeček, Oldřich (referee) ; Skalka, Petr (advisor)
This bachelor thesis focuses on micro-cellular impact absorbers. The micro-cellular absorber converts the kinetic energy of the impacting object into the strain energy of the internal structure of the absorber. The thesis focuses on two types of absorbers, namely the absorber with internal auxetic structure and the absorber with internal non-auxetic structure. The same porosity has been kept for both internal structures for further comparison of the characteristics of both the absorbers. As part of this thesis, an impact test was simulated. In this test, objects (cylinders) of different diameters, the same length (identical to the absorber thickness), and different kinetic energy were impacted into the absorber. The finite element method (explicit solution) was used to solve this problem. The output of the study was a comparison of simulations of the impact test into auxetic and non-auxetic structures.
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Design of the composite rotor sleeve of a high speed rotary machine
Pavlík, Ondřej ; Ševeček, Oldřich (referee) ; Návrat, Tomáš (advisor)
The diploma thesis focuses on manufacturing carbon fiber and epoxy composite material using filament winding method. Material properties of manufactured composite are ap-proximated using analytical and numerical homogenization models. Calculated material properties are applied to design and evaluate reserve factor of retaining sleeve for high speed brushless permanent magnet synchronous motor. Margin of safety of designed rotor is evaluated using composite failure criteria. Test stand for both static and dynamic testing is designed, static test stand is manufactured and assembled. Static strength test is carried out.
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Mechanical analysis of historical systems
Bilík, Pavel ; Ševeček, Oldřich (referee) ; Fuis, Vladimír (advisor)
This work thesis deals with historical machine systems from the period of antiquity and the Middle Ages. The basic concepts, quantities and phenomena related to the operation of machines are defined. Technically important inventions are described in more detail herein. In the practical part, two selected assemblies are examined, their dimensions and properties are designed. Furthermore, calculations from mechanical analysis are performed on selected systems. Numerical solutions are implemented using scripts in Matlab.
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Mutual interaction of multiple cracks growing in the particulate composite with brittle matrix under conditions of sub-critical crack growth
Slávik, Ondrej ; Ševeček, Oldřich (referee) ; Majer, Zdeněk (advisor)
In the first part of the submitted diploma thesis, the knowledge in the sphere of the fracture mechanics, related to the practice part of this thesis are summarized. In that the 2D parametrical numerical model of the particle composite with multiple cracks was created, using the finite elements method. Thanks to this model it is possible to find specific configurations which are showing the existance of multiple mutual interactions between these cracks, just by simple manipulation of the input data. In the calculations the influence of the residual stresses was considered which are formed during production of the material. The effect of the subcritical crack growth was taken into account as well in this thesis.
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Stress-Strain Calculations of Selected Components of Firearm
Pavlík, Ondřej ; Ševeček, Oldřich (referee) ; Slažanský, Martin (advisor)
Thesis deals with the utilization of the finite element method (FEM) in development of computational model. Subject of the computational model is the slide stop pin of the pistol CZ 75, designed and manufactured in Czech Republic by Česká zbrojovka Uherský Brod. The computational model describes strain stress analysis of the slide stop pin. The results of the analysis are subject to difficult sourcing of relevant and reliable input information. Based on stress strain analysis results, the safety factor of the pin was determined. However, the results are influenced a lot by input parameters selection. At the conclusion the summary of proposed further steps for computational model accuracy increase is proposed.
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Analytical model of composite cantilever with SMART layer
Dostal, Vojtěch ; Ševeček, Oldřich (referee) ; Majer, Zdeněk (advisor)
This bachelor's thesis deals with analytical modelling of composite cantilever with smart layer. The structure is based on the real piezoelectric generator, which is a solid cantilever beam with a layer of piezoelectric material attached to its bottom and top. The first part of this bachelor's thesis summarizes the knowledge of the energy harvesting, the process under which harvesting of electric energy from the piezoelectric generator belongs. Some piezoelectric materials are mentioned and described afterwards. At first, analytical modelling is implemented on the homogeneous cantilever beam. Then, the relations for required characteristics are derived for laminate structure, which is structurally similar to the piezoelectric generator. One chosen parameter will be changeable. Due to the ties of relations, the required characteristics will change as well, which are for the piezoelectric generator strain and deflection.
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