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Determination of residual fatigue lifetime of railway axle after surface treatment
Pánek, Ondřej ; Poduška, Jan (referee) ; Náhlík, Luboš (advisor)
This master thesis deals with prediction of residual fatigue lifetime of railway axle. In the first part of this thesis, theoretical introduction to the issue based on research of available literature is elaborated. The second part is dedicated to numerical modelling of actual railway axle with crack, which serves to obtain the necessary parameters entering estimation of the residual fatigue lifetime. At first, a finite element model of cylindrical body with crack loaded by bending moment was created and compared with analytical solution for verification purposes. The second step was the creation of separate models of railway axle with crack for three types of loading – bending moment, press fit of wheel and residual stresses, respectively. Furthermore, the shape of various crack propagation stages was determined, according to the methodology developed at IPM CAS. Using the determined crack shape, stress intensity factors were calculated separately from all types of loads for various crack depths. Dependence of stress intensity factor on the crack length was then used to calculate residual fatigue life for real loading spectrum.
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Methods for topology optimization of mechanically loaded structures and their application on trusses
Pánek, Ondřej ; Lošák, Petr (referee) ; Ševeček, Oldřich (advisor)
This bachelor thesis deals with a topology optimization of truss structures. In the first part of this thesis an overview of individual methods of the structural optimization and brief description of their principle based on recherche of available literature is given. The second part of the thesis deals with an application of selected methods to the topology optimization of truss structures, employing the computational codes programmed in the MATLAB software. In the first step, a code for computation of stresses in individual trusses and displacements in nodes of the truss structure by the finite element method was programmed. This code was later used in individual topology optimization codes for computation of parameters mentioned above. Selected topology optimization methods and their computational codes were then used for optimization of two model tasks – bridge and cantilever beam subjected to isolated forces, in order to reduce their weight while maintaining safety to the limit states of elasticity and buckling stability. At the end of the thesis, gained results were compared to results available in literature (nevertheless optimized as a continuum structure) and it can be concluded, that both these results are in a very good agreement.
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Determination of residual fatigue lifetime of railway axle after surface treatment
Pánek, Ondřej ; Poduška, Jan (referee) ; Náhlík, Luboš (advisor)
This master thesis deals with prediction of residual fatigue lifetime of railway axle. In the first part of this thesis, theoretical introduction to the issue based on research of available literature is elaborated. The second part is dedicated to numerical modelling of actual railway axle with crack, which serves to obtain the necessary parameters entering estimation of the residual fatigue lifetime. At first, a finite element model of cylindrical body with crack loaded by bending moment was created and compared with analytical solution for verification purposes. The second step was the creation of separate models of railway axle with crack for three types of loading – bending moment, press fit of wheel and residual stresses, respectively. Furthermore, the shape of various crack propagation stages was determined, according to the methodology developed at IPM CAS. Using the determined crack shape, stress intensity factors were calculated separately from all types of loads for various crack depths. Dependence of stress intensity factor on the crack length was then used to calculate residual fatigue life for real loading spectrum.
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Methods for topology optimization of mechanically loaded structures and their application on trusses
Pánek, Ondřej ; Lošák, Petr (referee) ; Ševeček, Oldřich (advisor)
This bachelor thesis deals with a topology optimization of truss structures. In the first part of this thesis an overview of individual methods of the structural optimization and brief description of their principle based on recherche of available literature is given. The second part of the thesis deals with an application of selected methods to the topology optimization of truss structures, employing the computational codes programmed in the MATLAB software. In the first step, a code for computation of stresses in individual trusses and displacements in nodes of the truss structure by the finite element method was programmed. This code was later used in individual topology optimization codes for computation of parameters mentioned above. Selected topology optimization methods and their computational codes were then used for optimization of two model tasks – bridge and cantilever beam subjected to isolated forces, in order to reduce their weight while maintaining safety to the limit states of elasticity and buckling stability. At the end of the thesis, gained results were compared to results available in literature (nevertheless optimized as a continuum structure) and it can be concluded, that both these results are in a very good agreement.
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