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Ductile Fracture Criteria in Multiaxial Loading – Theory, Experiments and Application
Šebek, František ; Horyl, Petr (oponent) ; Španiel, Miroslav (oponent) ; Petruška, Jindřich (vedoucí práce)
This thesis is concerned with ductile fracture, which is a result of multiaxial quasi-static monotonic loading accompanied with large plastic deformations, while the local approach is considered for material degradation. In computations, the damage evolution is governed by used ductile fracture criteria. These were theoretically studied in the introduction, and the calibration procedure was proposed after the choice of suitable fracture criterion. Next, the experimental program was designed, and the tests on aluminium alloy 2024-T351, concerning tension, torsion and compression, were realized at a room temperature for the investigation of damage accumulation and reliable calibration of chosen phenomenological ductile fracture criterion, expressed through the fracture strain, and dependent on the hydrostatic pressure and deviatoric stress tensor. The ductile fracture model was then coupled with the yield criterion. Plasticity was considered in the form of taking into account the state of third invariant of deviatoric stress tensor as well for investigated material. The whole proposed approach that is fully applicable to multiaxial problems was implemented using user subroutine into the commercial software, based on the explicit finite element method. In the end, the application of the proposed approach to modelling of ductile fracture is presented in the form of verification using chosen specimens, resulting in the conclusions and recommendations for future studies.
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Computational simulation of pass rolling
Hacek, Samuel ; Šebek, František (oponent) ; Petruška, Jindřich (vedoucí práce)
This master's thesis reviews possibilities of finite element modelling of pass rolling. Motivation and problem formulation may be found at the beginning of the thesis, followed by definition of system of essential variables. Next chapter describes various methods of rolling as well as the rolling process itself. An emphasis is put mainly on pass roll design. The following part deals with material behavior and its modelling in finite element software Abaqus, which is used in the computational part of the thesis. Multiple models of plasticity are introduced here, as well as damage criteria, used to assess material formability or simulate propagation of ductile damage through the material. Next part is focused on finite element method, specifically its explicit algorithm, later employed in the computational part of the thesis. In the last theoretical chapter, basic principles of photoelasticimetry, a traditional experimental method, are described. These chapters also contain description of simplified finite element analysis and photoplastic experimental analysis of a specific pass rolling problem. Computational model used there served as a basis for the new finite element model, creation of which is the purpose of the following chapter. Two variants of the simplified, previously used computational model were recreated as well. Structural analyses were carried out using the three created models and various results were evaluated. Summary of obtained results and their comparison to original computational and experimental results follows. Discussion of the results and evaluation of usability and reliability of individual computational models form conclusion of the thesis.
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Analýza svarů s využitím metody konečných prvků
Štěrba, Martin ; Kala, Jiří (oponent) ; Hradil, Petr (vedoucí práce)
Práce se zabývá numerickou analýzou svařovaných hliníkových konstrukcí. U těchto konstrukcí dochází v důsledku svařování k výraznému poklesu mechanických vlastností v místě svaru a tepelně ovlivněné oblasti. V rámci práce byly provedeny simulace kvazi staticky zatěžovaných svarových spojů ze slitiny EN AW-6082 T6 za účelem stanovení únosnosti a duktility těchto spojů. Pro výpočty byl použit programový systém na bázi explicitní metody konečných prvků. K vystižení anizotropie materiálu byl zvolen nelineární materiálový model s označením Weak texture model. Materiálové vlastnosti svaru a tepelně ovlivněné oblasti byly uvažovány odlišné od základního materiálu. Potřebné materiálové parametry byly převzaty z dostupné literatury, byly však popsány materiálové testy a procedura stanovení těchto parametrů. Ze srovnání výsledků numerických simulací s experimentálními daty vyplynula poměrně dobrá schopnost modelů vystihnout únosnost vyšetřovaných svarových spojů. Nicméně, z důvodu citlivosti modelů na velikost sítě konečných prvků, způsobenou problémem s lokalizací deformace, nebylo možné stanovit duktilitu těchto spojů.
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Deformačně-napěťová analýza tenkostěnné skříně vystavené rázovému zatížení od výbuchu
Tatalák, Adam ; Peč, Michal (oponent) ; Návrat, Tomáš (vedoucí práce)
Předkládaná diplomová práce se zabývá deformačně-napěťovou analýzou zjednodušeného modelu tenkostěnné transformátorové skříně vystavené rázovému zatížení od elektrického výbuchu. Ten je v tomto případě nahrazen výbuchem chemickým, čili výbuchem konvenční trhaviny. Problém je řešen pomocí výpočtového modelování s využitím metody konečných prvků prostřednictvím programu LS-DYNA. Po úvodu zabývajícím se teorií detonace a šířením rázových vln, je představen analytický přístup řešení, který slouží k verifikaci výsledků. V další kapitole je provedena rešerše použitelných metod řešení, z nichž byla k simulaci vybrána ALE metoda. V předběžné studii je analyzován vliv velikosti sítě, který je zaměřen na nalezení takové velikosti prvku, která by byla ještě výpočtově efektivní a výsledky by dosahovaly požadované přesnosti. Dále je zkoumán vliv vstupních podmínek (tvar, poloha a parametry výbušniny, poloha detonačního bodu, okrajové podmínky) na celkové rozložení a časový průběh tlaku. V dalším je analyzován vliv otvoru v horní části skříně na celkovou redistribuci tlaku a deformaci a napjatost skříně. Je také provedena deformačně-napěťová analýza dveří skříně, jejichž připevnění je modelováno pomocí více druhů kontaktů. Tyto jsou poté zkoumány z hlediska jejich tuhosti.
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The use of mass scaling within Abaqus explicit code
Hacek, Samuel ; Kubík, Petr (oponent) ; Šebek, František (vedoucí práce)
The purpose of this bachelor’s thesis is to evaluate the usability of the mass scaling function in Abaqus computing environment. The introductory part starts with a description of the explicit formulation of the finite element method, which is followed by a definition of various mass scaling methods and a description of their usability. The practical part of the thesis consists of a few problems solved using aforementioned mass scaling techniques. The course of the solution is focused on the determination of the extent of the influence that the use of various mass scaling techniques has on the obtained data. The last part of the thesis is devoted to evaluation of the applicability of various mass scaling techniques in different situations, considering possible reduction of computing time as well as the reliability of the obtained data.
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Computational simulation of pass rolling
Hacek, Samuel ; Šebek, František (oponent) ; Petruška, Jindřich (vedoucí práce)
This master's thesis reviews possibilities of finite element modelling of pass rolling. Motivation and problem formulation may be found at the beginning of the thesis, followed by definition of system of essential variables. Next chapter describes various methods of rolling as well as the rolling process itself. An emphasis is put mainly on pass roll design. The following part deals with material behavior and its modelling in finite element software Abaqus, which is used in the computational part of the thesis. Multiple models of plasticity are introduced here, as well as damage criteria, used to assess material formability or simulate propagation of ductile damage through the material. Next part is focused on finite element method, specifically its explicit algorithm, later employed in the computational part of the thesis. In the last theoretical chapter, basic principles of photoelasticimetry, a traditional experimental method, are described. These chapters also contain description of simplified finite element analysis and photoplastic experimental analysis of a specific pass rolling problem. Computational model used there served as a basis for the new finite element model, creation of which is the purpose of the following chapter. Two variants of the simplified, previously used computational model were recreated as well. Structural analyses were carried out using the three created models and various results were evaluated. Summary of obtained results and their comparison to original computational and experimental results follows. Discussion of the results and evaluation of usability and reliability of individual computational models form conclusion of the thesis.
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The use of mass scaling within Abaqus explicit code
Hacek, Samuel ; Kubík, Petr (oponent) ; Šebek, František (vedoucí práce)
The purpose of this bachelor’s thesis is to evaluate the usability of the mass scaling function in Abaqus computing environment. The introductory part starts with a description of the explicit formulation of the finite element method, which is followed by a definition of various mass scaling methods and a description of their usability. The practical part of the thesis consists of a few problems solved using aforementioned mass scaling techniques. The course of the solution is focused on the determination of the extent of the influence that the use of various mass scaling techniques has on the obtained data. The last part of the thesis is devoted to evaluation of the applicability of various mass scaling techniques in different situations, considering possible reduction of computing time as well as the reliability of the obtained data.
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Analýza svarů s využitím metody konečných prvků
Štěrba, Martin ; Kala, Jiří (oponent) ; Hradil, Petr (vedoucí práce)
Práce se zabývá numerickou analýzou svařovaných hliníkových konstrukcí. U těchto konstrukcí dochází v důsledku svařování k výraznému poklesu mechanických vlastností v místě svaru a tepelně ovlivněné oblasti. V rámci práce byly provedeny simulace kvazi staticky zatěžovaných svarových spojů ze slitiny EN AW-6082 T6 za účelem stanovení únosnosti a duktility těchto spojů. Pro výpočty byl použit programový systém na bázi explicitní metody konečných prvků. K vystižení anizotropie materiálu byl zvolen nelineární materiálový model s označením Weak texture model. Materiálové vlastnosti svaru a tepelně ovlivněné oblasti byly uvažovány odlišné od základního materiálu. Potřebné materiálové parametry byly převzaty z dostupné literatury, byly však popsány materiálové testy a procedura stanovení těchto parametrů. Ze srovnání výsledků numerických simulací s experimentálními daty vyplynula poměrně dobrá schopnost modelů vystihnout únosnost vyšetřovaných svarových spojů. Nicméně, z důvodu citlivosti modelů na velikost sítě konečných prvků, způsobenou problémem s lokalizací deformace, nebylo možné stanovit duktilitu těchto spojů.
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Ductile Fracture Criteria in Multiaxial Loading – Theory, Experiments and Application
Šebek, František ; Horyl, Petr (oponent) ; Španiel, Miroslav (oponent) ; Petruška, Jindřich (vedoucí práce)
This thesis is concerned with ductile fracture, which is a result of multiaxial quasi-static monotonic loading accompanied with large plastic deformations, while the local approach is considered for material degradation. In computations, the damage evolution is governed by used ductile fracture criteria. These were theoretically studied in the introduction, and the calibration procedure was proposed after the choice of suitable fracture criterion. Next, the experimental program was designed, and the tests on aluminium alloy 2024-T351, concerning tension, torsion and compression, were realized at a room temperature for the investigation of damage accumulation and reliable calibration of chosen phenomenological ductile fracture criterion, expressed through the fracture strain, and dependent on the hydrostatic pressure and deviatoric stress tensor. The ductile fracture model was then coupled with the yield criterion. Plasticity was considered in the form of taking into account the state of third invariant of deviatoric stress tensor as well for investigated material. The whole proposed approach that is fully applicable to multiaxial problems was implemented using user subroutine into the commercial software, based on the explicit finite element method. In the end, the application of the proposed approach to modelling of ductile fracture is presented in the form of verification using chosen specimens, resulting in the conclusions and recommendations for future studies.
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Ductile fracture criteria in multiaxial loading – theory, experiments and application
Šebek, František ; Petruška, Jindřich (vedoucí práce)
This thesis is concerned with ductile fracture, which is a result of multiaxial quasi-static monotonic loading accompanied with large plastic deformations, while the local approach is considered for material degradation. In computations, the damage evolution is governed by used ductile fracture criteria. These were theoretically studied in the introduction, and the calibration procedure was proposed after the choice of suitable fracture criterion. Next, the experimental program was designed, and the tests on aluminium alloy 2024-T351, concerning tension, torsion and compression, were realized at a room temperature for the investigation of damage accumulation and reliable calibration of chosen phenomenological ductile fracture criterion, expressed through the fracture strain, and dependent on the hydrostatic pressure and deviatoric stress tensor. The ductile fracture model was then coupled with the yield criterion. Plasticity was considered in the form of taking into account the state of third invariant of deviatoric stress tensor as well for investigated material. The whole proposed approach that is fully applicable to multiaxial problems was implemented using user subroutine into the commercial software, based on the explicit finite element method. In the end, the application of the proposed approach to modelling of ductile fracture is presented in the form of verification using chosen specimens, resulting in the conclusions and recommendations for future studies.
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