The master thesis is focused on estimation of crack propagation origin from sharp V-notch. Stress distribution around the tip of the V-notch is described on the base of generalized linear elastic fracture mechanics. The change of the stress singularity exponent caused by geometry of the V-notch and the vertex singularity is taken into account. The first part of the work is devoted to the estimation of the stress singularity exponent of the V-notch either from stress distribution around the tip of the V-notch or by using analytical solution. Formerly derived stability criteria are applied in the second part of the work. The origin of the crack propagation is estimated for several experimental specimens. The aim of this thesis is to compare the available experimentally observed data with results obtained using those criteria based on the application of generalized linear elastic fracture mechanics developer at the Institute of Physics of Materials Academy of Sciences of the Czech Republic. The finite element code Ansys and mathematical software Matlab were used for the necessary calculations.

This diploma thesis deals with creating of finite element model for the analysis of acustic waves radiation through human vocal tract and through the head surrounding space. The thesis contains a short overview of the anatomy of relevant parts and a short overview of formerly published models relevant to the topic. Then the process of creating the 3D model of human head, including the vocal tract, based on CT scans, and the mesh itself follows. This is succeeded by the computational solution taking in the acount the acoustic absorption of the vocal tract walls and radiation into the open space. The results gained are compared to relevant literature on this topic. The changes in frequency spectra in specific nodes of the mesh are reviewed and compared to relevant literature on the topic. The results could be used as basis of eventual frequention corrections of microphones used for voice diagnosis or registration in general, eg of speach or singing.

In this thesis is wrote up a complete procedure of stator core stiffness determination using finite element method (FEM), subsequently, the stator core stiffness database was created according to this procedure. In the next chapter is carried out a sensitivity analysis of one chosen stator core, which led to identifying parameters that affected its stiffness the most. Finally, a modal analysis of one synchronous machine was performed using FEM, in order to determine the effect of stator core stiffness on modal characteristics of the machine. Several modal shapes and corresponding natural frequencies were computed in this analysis, then only a few shapes with the highest core effect were chosen and compared.

Metal additive technology allows to create objects with complex shape that are very difficult to produce by conventional technologies. An example of such component is a porous structure which is composed of periodical truss cells. This diploma thesis deals with the prediction of the mechanical properties of very small lattice structures made of additive manufacturing technology Selective Laser Melting. Using the proposed test specimens it was found that real dimensions of the trusses varies with size and orientation to the base platform. It was proposed and tested samples for rod tensile test made of SLM. Based on the real information about dimensions and mechanical properties of rods were predicted mechanical properties of lattice structures. A lot of mechanical tests were carried out to obtain the real mechanical properties. Test results and conclusions are described in the thesis.

The main goal of this work is the comparison of the size of the plastic zone at the crack tip for two analysis methods: an analytical linear method and an elastic-plastic analysis employing the Finite Element method (ANSYS software). All calculations were made for a crack loaded under pure shear modes. These types of loading are not sufficiently described in the literature. The first part of this work introduces the problem with the crack tip plastic zone using both linear and nonlinear fracture parameters. The second part is dedicated to the construction of the Finite Element model in the ANSYS software. The geometry of the samples and the loading levels were chosen to match an existing experimental test of the impact of shear modes on the crack behavior. In the third part of this thesis, the plastic zone radii for pure shear modes II and III are estimated using several methods and the results are compared. In the last part of this work, the same procedure as in the previous part is applied on a mixed-mode II+III loading. A result of this thesis is the assessment of the application limits of the linear analysis method used to estimate the size of the plastic zone at the crack tip for a specific geometry and material model.

The following master thesis deals with creating a computational model for acoustic wave distribution by the human vocal tract and then the space around a human head. Detailed mapping of the sound field around the human head is important for more accurate measurement of the human voice. Part of this work is the creation of three-dimensional finite element model of the human head and the vocal tract during phonation of the vowel /:a/ based on the data from the computational tomography. Further the literature search of the function of the vocal tract, biomechanics of the making of the human voice, an overview of the computational models so far published in the literature and in literature reported measurements of the distribution of the human voice by the vocal tract and then in the space around the head . The following is the actual numerical solution of the acoustic waves distribution from the vocal cords through the vocal tract and then the space around the human head when thinking of acoustic absorption on the walls of the vocal tract and on the skin of the head for different types of waking of the model. The results are compared with previously published measurements of the distribution of the human voice and mainly the distortion of the frequency spectra at each specific node in the space around the head and in its vicinity of where the sensor microphones are typically placed are analyzed. Results of the computational modeling will eventually be used for frequency correction for various positions of the microphones scanning the voice distribution in its diagnosis, speech or singing.

This diploma thesis deals with an application of the finite element method on elastohydrodynamic (EHD) lubrication simulations. Commercially available software COMSOL is used for the computation, while two different modules for modeling EHD lubrication are described in a detail. Firstly, a new approach using the module Thin-Film Flow is developed, considering and describing some limitations of this approach. This is the very first published work dealing complex with EHD simulation in Thin-Film Flow module. In the second part of the thesis, there was created a model of line contact using the module for the introduction of partial differential equations (PDE). The model is partially verified with available works for different values of the input parameters. Subsequently, the velocity effect of the contact surfaces on the pressure and the lubricant thickness in contact is analyzed. Finally, the last part is examines the influence of the values of some parameters on the final value of the contact pressure and the lubricant thickness, as well as on numerical stability of the entire model.

This thesis describes complex modeling of asynchronous motor by finite element method. Complex modeling concerns to making models based on different physical principles and their connection. Models are made in Ansys program components and their connection is made in program Ansys Workbench. This thesis includes creating electromagnetic model, thermal model, mechanical model and coupled model which connect partial models.

The presented diploma thesis builds on author’s bachelor’s thesis of the similar name which was focused, in particular, on rhizarthrosis. Because of this joint disease, implantations of the total joint replacement are performed. The bachelor’s thesis also served as a familiarization with the finite element method and contact analyses issues, giving a theoretical framework for this diploma thesis. As opposed to that, the diploma thesis aims entirely at deformation and stress analysis of the total replacement. The main objective is to carry out analyses of different variants of geometric models. In addition, there is a tendency to analyze contact pressures of advanced model concerning all the total replacement, bone tissues, ligaments and tendons guaranteeing the static equilibrium of components. The bachelor’s thesis has been developed in ANSYS Workbench, whereas the diploma thesis in ANSYS APDL. Work in APDL allows user to control better over the entire computational process, however, requires more skills and theoretic knowledge. Contact analyses bring a lot of problems associated with convergence of procedures and accuracy of results. Therefore, explanations of important terms and set of recommendations are included for the purpose of easier solving of the contact problems.

The topic of this diploma thesis is the frame of the foundry trolley crane 330/65/20t. The crane crab is used for handling with molten metal. The frame is analyzed by strength inspection and fatigue strength inspection. The process is according to ČSN EN 13001. The analyses are made by using finite element method on a beam and shell models. The diploma thesis was made in cooperation with the Královopolská a.s. company.