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Failure probability of the ceramics part using Weibull weakest link theory
Kovář, Jaroslav ; Návrat, Tomáš (referee) ; Fuis, Vladimír (advisor)
This thesis compares Weibull weakest link theory with inclusion of one and all three principal stresses. Principal stresses needed for this theory were calculated with finite element method. The informational research is in the introduction of this thesis. It includes ceramic materials, Weibull weakest link theory, Gaussian quadrature over spherical surface and ceramic head of hip joint endoprothesis. Theoretical part is used for next calculations of probability of failure. The probability of failure of ceramic rod loaded by four-point bending is calculated in first calculations. This task is solved as contact in the next step. Next part of this thesis is about selection of suitable method of numerical integration. This method will be used in the calculation with all three principal stresses. The results of calculation with all three principal stresses are compared with the results of the calculation which includes only first principal stress. Firstly, this is done for cylindrical body and then used on head of hip joint endoprothesis. In the last part of this thesis, probability of fracture of head hip joint endoprothesis with shape deviation of nominal conicity is calculated.
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The use of superelements in solving large systems of MKP
Hluška, Milan ; Halabuk, Dávid (referee) ; Návrat, Tomáš (advisor)
This bachelor thesis deals with the utilization of superelements in finite element method simulations. First, the basic theory of FEM and superelements is explained. The principles and procedures of using superelements in ANSYS and its scripting language APDL is described next. Third part focuses on custom-made program that illustrates the appication of superelements, and its results of an exemplary calculation are compared with the results from ANSYS APDL in the last part.
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Application of optical methods for determining the deformation of bodies
Kováříková, Sabina ; Šebek, František (referee) ; Návrat, Tomáš (advisor)
This Bachelor’s thesis is focused on application of digital image correlation method for determining the deformation of bodies. It contains theoretical knowledge about this method and realization of measurements on selected bodies. The aim of the thesis is to compare experimentally obtained results with the results, obtained in software Ansys Workbench. The Bachelor’s thesis also contains characteristics of other optical methods, used for determining the deformation of bodies and research of software, which can be used for data processing, based on DIC method.
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The usage of Salome Meca workbench for task solution in the field of solid mechanics
Nytra, Michal ; Návrat, Tomáš (referee) ; Vosynek, Petr (advisor)
Submitted bachelors thesis deals with solution of tasks of body mechanics in open-source workbench Salome Meca and FEM solver Code_Aster. In the beginning is short theoretical introduction to finite element method a basic theory to strength of materials. Then follows series of tasks, which will test solver and workbench. We will compare results with analytical solution (if exists), eventually with available commerical software Ansys. There are 3 static structural tasks (beams, axisymetric bodies). Next task is from dynamics, searching of natural frequencies and vibration of plate during harmonic excitation. The last one is steady-state-thermal combined with static structural. In the conclusion are summarized advantages and disadvantages of open-source softwares. Results of workbench Salome Meca vary from analytical solution maximal to 10 %, what is in engineering praxis suffcient accuracy.
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Pevnostní posouzení konstrukce výřezu dveří přetlakovatelného habitatu pro extrémní prostředí
Sláma, David ; Šálený, Vratislav (referee) ; Návrat, Tomáš (advisor)
Main goals of this master thesis are following: to perform the state of the art research of overpressure constructions (especially space habitats, plane fuselages); to create an own concept of the functional inside ending (hole) in the sandwich panel for a door; to perform stress-strain analysis of this concept; to perform the design optimalization of this concept in order to minimise the weight. To solve the problems above software Ansys 17.2 is chosen, because it allows to: model the material of the honeycomb core of sandwich panel as homogenous linear orthotropic material; evaluate reserve factors of all critical limit states; perform the design optimalization; perform Monte Carlo simulation. First and second design optimalizations discover, that with defined parameters: 0,635 mm width of aluminium sandwich face sheets and inner overpressure 0,1 MPa, a creation of the model, that would be safe by changing the values of design variables is not possible. Specifically, the maximum value of shear stress on the glued areas between aluminium face sheets and honeycomb core is higher than the shear strength of the glue. Therefore, two new concepts are created. First for inner pressure 0,03 MPa and bigger width of aluminium face sheets 3,175 mm, second for inner pressure 0,02 MPa and same width of aluminium face sheets 0,635 mm. For both these concepts, an overall reserve factor is calculated. First, the value of an overall reserve factor is calculated deterministically. Secondly, the value of an overall reserve factor is calculated stochastically considering the variance of material properties of the honeycomb core ± 10 % by Monte Carlo simulation. An overall reserve factor of the concept with inner pressure 0,02 MPa is determined as 1,21. An overall reserve factor of the concept with inner pressure 0,03 MPa is determined as 1,20. The weight of the concept for inner pressure 0,03 MPa is though 4 times bigger than the weight of the concept for inner pressure 0,02 MPa. In the concept for inner pressure 0,02 MPa the maximum value of HMH stress in aluminium components is critical, stochastically considered material properties of the honeycomb core don’t have a significant influence on this value. In the concept for inner pressure 0,03 MPa the value of maximum shear stress on the glued areas between aluminium face sheets and the honeycomb core is critical, stochastically considered material properties of the honeycomb core have a significant influence on this value. In the concept for inner pressure 0,03 MPa an absolute error of overall reserve factor is 8 % (overall reserve factor calculated deterministically was 1,28) which is significant. Monte Carlo simulation is also used to find that the value of Poisson ratio XY of the honeycomb core doesn’t have statistically significant influence on all limit states. Value of the reserve factor of the honeycomb core is higher than 2 in both concepts. Monte Carlo simulation discovers that this value can be significantly lower. Using Tsai-Wu failure criteria the reserve factor in the concept for inner pressure 0,02 MPa is determined as 2,72 deterministically x 2,41 stochastically (absolute error 31 %), in the concept for inner pressure 0,03 MPa the reserve factor is determined as 6,85 deterministically x 6,17 stochastically (absolute error 68 %).
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Thermal Contact Resistance Under High Temperature
Kvapil, Jiří ; Návrat, Tomáš (referee) ; Brestovič, Tomáš (referee) ; Horský, Jaroslav (advisor)
Nowadays numerical simulations are used to optimize manufacturing process. These numerical simulations need a large amount of input parameters and some of these parameters have not been sufficiently described. One of this parameter is thermal contact resistance, which is not sufficiently described for high temperatures and high contact pressure. This work describes experimental measuring of thermal contact resistance and how to determine thermal contact conductance which can be used as a boundary condition for numerical simulations. An Experimental device was built in Heat Transfer and Fluid Flow Laboratory, part of Brno University of Technology, and can be used for measuring thermal contact conductance in various conditions, such as contact pressure, initial temperatures of bodies in contact, type of material, surface roughness, presence of scales on the contact surface. Bodies in contact are marked as a sensor and a sample, both are embedded with thermocouples. The temperature history of bodies during an experiment is measured by thermocouples and then used to estimate time dependent values of thermal contact conductance by an inverse heat conduction calculation. Results are summarized and the dependence of thermal contact conductance in various conditions is described.
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The usage of Salome Meca workbench for task solution in the field of solid mechanics
Anděl, Tomáš ; Návrat, Tomáš (referee) ; Vosynek, Petr (advisor)
Presented bachelor’s thesis focuses on solving basics tasks in the field of solid me-chanics by the finite-element open-source software Salome Meca. The theoretical background of finite element method (FEM), general explanation of basic expressions and brief summary of today’s used open-source and commercial software too is intro-duced in the opening part of the thesis. The brief overview of Salome Meca compu-ting environment and then file of individual tasks solved by using this software are followed. Acquired results are later compared with the other numerical software (ANSYS Workbench) or with analytical solutions.
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