Theoretical and numerical issues on ductile failure prediction - an overview

• Autorzy: Cesar de Sa J. M. A. , Andrade F. X. C. , Andrade Pires F. M.

Warianty tytułu

PL

Problemy teoretycznej i numerycznej analizy plastycznego pękania - wybrane zagadnienia

• Języki publikacji: EN

Abstrakty

EN

The main goal of this paper is to give a general overview of some of the recent advances accomplished in the description of ductile damage, both from a theoretical and numerical point of view. To start with, the classical local theory with regard to the thermodynamics of irreversible processes is reviewed where a general elasto-plastic damage model is established. It is also highlighted the assumptions and limitations behind the classical theory when the constitutive equations are obtained from the solution of a constrained maximisation problem. Recent advances on the non-local modelling of ductile damage are also addressed where we shed some light on the principles and consequences of non-locality in elasto-plastic damage models. The issues regarding the efficient numerical implementation of both local and non-local theories are also discussed where special attention is devoted to the implementation of non-local models. In particular, a novel computational strategy, suitable for implementations in commercial programs, is presented for the explicit finite element code LS-DYNA in detail. A FORTRAN code excerpt is given in which the main steps for the implementation of the model are schematically depicted. The effectiveness of the non-local model is assessed through the simulation of an axisymmetric specimen and a sheet metal forming process. It is shown that in both cases the non-local numerical strategy is able to diminish the pathological mesh dependency inherently present in local elasto-plastic damage models.

PL

Celem pracy jest przedstawienie przeglądu najnowszych osiągnięć w zakresie opisu plastycznego pękania, zarówno od strony teoretycznej jak i numerycznej. Na wstępie omówiono klasyczną lokalną teorię odnoszącą się do termodynamiki nieodwracalnych procesów, wykorzystywaną do opisu ogólnego modelu sprężysto-plastycznego pękania. Naświetlono również założenia i ograniczenia klasycznej teorii pojawiające się wtedy, kiedy równania konstytutywne są uzyskiwane z rozwiązania problemu minimalizacji z ograniczeniami. Omówiono też ostatnie osiągnięcia w zakresie nie lokalnego modelowania sprężysto-plastycznego pękania, pokazując zasady i konsekwencje wynikające z nie lokalnego traktowania tego procesu. Zagadnienia związane z efektywnym numerycznym opisem lokalnej i nielokalnej teorii są również omówione w pracy, a specjalną uwagę poświęcono implementacji modeli nie lokalnych. Nowa strategia obliczeniowa, umożliwiająca implementację tych modeli w komercyjnych programach symulacyjnych, została szczegółowo przedstawiona na przykładzie LS-DYNA. Fragmenty kodu w języku FORTRAN, w których pokazano główne kroki implementacji, są przytoczone w pracy. Efektywność nie lokalnego modelu jest oceniona na podstawie symulacji odkształcania osiowosymetrycznych próbek oraz procesów tłoczenia. Wykazano, że w obydwóch analizowanych przypadkach nielokalna strategia numeryczna pozwala na obniżenie wrażliwości rozwiązania na rozmiar siatki, które jest nierozerwalnie związane ze sprężysto-plastycznymi modelami pękania.

Słowa kluczowe

EN

ductile failure; damage; elasto-plasticity; non-local model; LS-DYNA user-defined material

• Wydawca: Wydawnictwa AGH
• Czasopismo: Computer Methods in Materials Science
• Rocznik: 2010
• Tom: Vol. 10, No. 4
• Strony: 279--293
• Opis fizyczny: Bibliogr. 36 poz., rys.

Twórcy

autor

Cesar de Sa J. M. A.

autor

Andrade F. X. C.

autor

Andrade Pires F. M.

• Department ofMechanical Engineering - DEMec Faculty of Engineering, University of Porto - FEUP Rua Dr. Roberto Frias 4200-465 Porto, Portugal,

Bibliografia

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