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A non-associated plasticity model for predicting ductile fracture of metallic materials
Vobejda, Radek ; Kotoul, Michal (referee) ; Halama, Radim (referee) ; Šebek, František (advisor)
This thesis is focused on the study of the applicability of plasticity models based on associated and non-associated flow rule for the prediction of ductile fracture of metallic materials. Firstly, a new isotropic plasticity model is proposed based on the non-associated flow rule, which guarantees the convexity of the yield surface by its definition for any combination of material coefficients. This model, together with models adopted from the literature, is calibrated on the experiments carried out on aluminium alloy 2024-T351. The state variables obtained from numerical simulations of experiments using different plasticity models are used to calibrate the ductile fracture criteria. Numerical simulations indicate that using a non-quadratic plasticity model based on a non-associated flow rule gives the best agreement with experiments in terms of force responses and deformations. The calibrated ductile fracture criterion is further used to simulate the fracture of the experimental specimens used for calibration and to design additional experimental specimens. Finally, an experimental program is designed on this aluminum alloy to map the anisotropy of the material and based on the obtained experimental data, the proposed isotropic plasticity model is extended to anisotropy, calibrated and compared to several models from literature.
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Computational modeling of 3D printing structures made of PET-G material
Michálek, Mojmír Cyril ; Halama, Radim (referee) ; Vosynek, Petr (advisor)
Master’s thesis deals with computational modeling of 3D printing process done by FDM method made from PETG material using finite element method. Research section contains a brief description of 3D printing process modeling possibilities using finite element method and summarizes fundamental mechanical properties of thermoplastics. In practical section there is an evaluation of specimens printed of PETG material tensile tests. Further there is performed a sensitivity analysis of various influences on vertical imperfection of printed part Idler and is done its design modification, which is based on results of this analysis.
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Development and implementation of 3D geometry extraction method for topological optimization
Šotola, M. ; Rybanský, D. ; Maršálek, P. ; Halama, R. ; Kopačka, Ján ; Ježek, Ondřej ; Gabriel, Dušan ; Tejc, J. ; Pašek, M. ; Kovář, L.
This research report TN01000024/08-V012 is an output of the subtask of the project TN1000024/08 Automation and production system optimization, one of the objectives of which is to develop methods of post-processing of topological optimization (TO) results in cooperation with MECAS ESI Ltd. Three different smoothing approaches are discussed: the Taubin method, volume representation using radial basis functions and smoothing by remeshing using the Netgen library.
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Multi-Objective Optimization of Complex Composite Structures with Variable Stiffness
Symonov, Volodymyr ; Halama, Radim (referee) ; Píštěk, Antonín (referee) ; Juračka, Jaroslav (advisor)
Disertační práce se věnuje vývoji metodologií pro vice-cílovou optimalizací složitých kompozitních konstrukcí s proměnnou tuhosti. Vice úrovňový hybridní optimalizační algoritmus je založený na bázi hybridní optimalizační metody s využitím interpolační plochy odezvy, genetického algoritmu a jednoparametrické optimalizace. Pro strukturální analýzy je využit MKP software MSC Nastran. Nový genetický algoritmus a paralelní jednoparametrický optimalizační algoritmus na základě metody Zlatého řezu jsou vyvinuty pro metodologii. MKP software a vyvinuté optimalizační algoritmy jsou integrované pomoci komerčního optimalizačního softwaru Noesis Optimus od Noesis Solutions. Vyvinutá metodologie je ověřena pomoci testovací optimalizační úlohy.
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Review of methods for the post-processing of topological optimization results
Kopačka, Ján ; Ježek, Ondřej ; Gabriel, Dušan ; Šotola, Martin ; Rybanský, David ; Maršálek, Pavel ; Halama, R. ; Tejc, J. ; Pašek, M. ; Kovář, L.
The research report is an output of the sub-project TN1000024/08: Automation and production system optimization in cooperation with MECAS ESI Ltd on the development of methods for post-processing of topological optimization (TO) results. In this report a detailed survey of these methods is introduced as necessary tool for seamless integration of the results TO with subsequent numerical simulations and additive manufacturing. The selected method for post-processing based on a level-set approach using radial basis functions has been implemented and successfully tested on a well-known 2D Messerschmitt-Bölkow-Blohm (MBB) beam test problem.
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Creep behaviour of 316L stainless steel prepared by 3D printing
Dymáček, Petr ; Kloc, Luboš ; Gabriel, Dušan ; Masák, Jan ; Pagáč, M. ; Halama, R.
The 3D printed 316L stainless steel produced by selective laser melting (SLM) was subjected to short term creep testing at 700 °C. Two directions of printing: i) horizontal and ii) vertical, were selected to test the creep performance of the steel. Comparison with the open literature data shows very good short-term creep properties of 3D printed steel that are superior to conventional steel. Both studied directions of printing show similar results so the steel can be considered from creep point of view as isotropic. The solution annealing prior to the creep testing slightly, but not substantially, lowers the creep performance of the steel.
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Computational modeling of 3D printing structures made of PET-G material
Michálek, Mojmír Cyril ; Halama, Radim (referee) ; Vosynek, Petr (advisor)
Master’s thesis deals with computational modeling of 3D printing process done by FDM method made from PETG material using finite element method. Research section contains a brief description of 3D printing process modeling possibilities using finite element method and summarizes fundamental mechanical properties of thermoplastics. In practical section there is an evaluation of specimens printed of PETG material tensile tests. Further there is performed a sensitivity analysis of various influences on vertical imperfection of printed part Idler and is done its design modification, which is based on results of this analysis.
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