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Author(s): Pedro Manuel Cardoso Teixeira
Francisco Manuel Andrade Pires
Abel Dias dos Santos
José Manuel de Almeida César de Sá
Title: Finite element prediction of fracture onset in sheet metal forming using a ductile damage model
Issue Date: 2006
Abstract: The ability to predict the formability limit of sheet metal forming processes is of paramount importance asthe finite deformation in these processes is restricted by geometric instabilities due to necking, strainlocalization and consequent ductile fracture. Although forming limit diagrams, associated with finite elementsimulations, are currently available, or are easy to implement, in powerful commercial codes, when complexstrain paths are involved, very often combined with an anisotropic behaviour, these predictions fail to givethe right answer.Ductile failure is a result of internal degradation described throughout metallographic observations by thenucleation, growth and coalescence of voids and micro-cracks that may lead to macroscopic collapse. Thefact that internal degradation (or damage) accompanies large plastic deformation suggests that these twodissipative processes, although different in nature, influence each other and should, therefore, be coupled atthe constitutive level. Consequently the theory of Continuum Damage Mechanics may provide a betterinsight to the physical phenomenon and play a significant role in the study of the formability and fractureonset in sheet metal forming processes.To address these problems a damage model is introduced in a commercial code. This model is based on theenhanced Lemaitres ductile damage evolution law, which includes a distinction between rates of damagegrowth observed for states of stress with identical triaxiality but stresses of opposite sign (tension andcompression), and is coupled with Hills orthotropic plasticity criterion. The resulting constitutive equationsare implemented and assessed for the prediction of fracture onset in sheet metal forming processes. Anumerical example has been carried out in order to assess the capability of the implemented model innecking prediction and its results were compared with experimental ones.
Subject: Engenharia mecânica, Engenharia mecânica
Mechanical engineering, Mechanical engineering
Scientific areas: Ciências da engenharia e tecnologias::Engenharia mecânica
Engineering and technology::Mechanical engineering
Source: IDDRG 2006 - International Deep Drawing Research Group Conference
Document Type: Artigo em Livro de Atas de Conferência Internacional
Rights: restrictedAccess
Appears in Collections:FEUP - Artigo em Livro de Atas de Conferência Internacional

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