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2016 | Buch

Multiscale Modelling in Sheet Metal Forming

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This book gives a unified presentation of the research performed in the field of multiscale modelling in sheet metal forming over the course of more than thirty years by the members of six teams from internationally acclaimed universities.

The first chapter is devoted to the presentation of some recent phenomenological yield criteria (BBC 2005 and BBC 2008) developed at the CERTETA center from the Technical University of Cluj-Napoca. An overview on the crystallographic texture and plastic anisotropy is presented in Chapter 2. Chapter 3 is dedicated to multiscale modelling of plastic anisotropy. The authors describe a new hierarchical multi-scale framework that allows taking into account the evolution of plastic anisotropy during sheet forming processes. Chapter 4 is focused on modelling the evolution of voids in porous metals with applications to forming limit curves and ductile fracture. The chapter details the steps needed for the development of dissipation functions and Gurson-type models for non-quadratic anisotropic plasticity criteria like BBC 2005 and those based on linear transformations. Chapter 5 describes advanced models for the prediction of forming limit curves developed by the authors. Chapter 6 is devoted to anisotropic damage in elasto-plastic materials with structural defects. Finally, Chapter 7 deals with modelling of the Portevin-Le Chatelier (PLC) effect.

This volume contains contributions from leading researchers from the Technical University of Cluj-Napoca, Romania, the Catholic University of Leuven, Belgium, Clausthal University of Technology, Germany, Amirkabir University of Technology, Iran, the University of Bucharest, Romania, and the Institute of Mathematics of the Romanian Academy, Romania. It will prove useful to postgraduate students, researchers and engineers who are interested in the mechanical modeling and numerical simulation of sheet metal forming processes.

Inhaltsverzeichnis

Frontmatter
Chapter 1. Plastic Behaviour of Sheet Metals
Abstract
Due to the rolling process, sheet metals generally exhibit a significant anisotropy. In fact, the rolling process induces a particular anisotropy characterised by the symmetry of the mechanical properties with respect to three orthogonal planes. Such a mechanical behaviour is called orthotropy. The intersection lines of the symmetry planes are the orthotropy axes. In the case of rolled sheet metals, their orientation is as follows: rolling direction (RD); transverse direction (TD); normal direction (ND).
Dorel Banabic, Dan-Sorin Comsa, Jerzy Gawad
Chapter 2. Crystallographic Texture and Plastic Anisotropy
Hans Joachim Bunge, Robert Arthur Schwarzer
Chapter 3. Multiscale Modelling of Mechanical Anisotropy
Jerzy Gawad, Albert van Bael, Paul van Houtte
Chapter 4. Modelling the Voids Growth in Ductile Fracture
Abstract
Ductile fracture in metals and metallic alloys is due to the evolution of microscopic voids during plastic deformation. Voids nucleate around foreign inclusions or at grain boundaries and grow in regions with large triaxial stresses. Larger voids promote the formation of bands of localized deformation where new small voids are nucleated, thus forming a macroscopic crack. The microscopic dimples present on ductile fracture faces are a direct proof for such a mechanism.
Mihai Gologanu, Dan-Sorin Comsa, Abdolvahed Kami, Dorel Banabic
Chapter 5. Advanced Models for the Prediction of Forming Limit Curves
Abstract
During the forming of flat sheet metal into a more complex shape, a number of plastic instabilities may occur subsequently. A ‘plastic instability’ occurs when the zone of plastic deformation is suddenly confined to a smaller zone. The first plastic instability which usually occurs in forming processes is the onset of diffuse necking, in which plastic deformation is confined to a smaller zone, but with typical dimensions that are still in the order of magnitude of the part’s dimensions.
Dorel Banabic, Dan-Sorin Comsa, Philip Eyckens, Abdolvahed Kami, Mihai Gologanu
Chapter 6. Anisotropic Damage in Elasto-plastic Materials with Structural Defects
Abstract
The aims of the chapter is to develop elasto-plastic models with anistropic damage, which are mathematically coherent, physically motivated and consistent with certain dissipation principle. A concise and critical presentation of the contributions and results which led to basic ideas for the development of elasto-plastic anisotropic damaged materials is exposed in Sects. 6.2 and 6.3. Two types of constitutive models have been proposed in Sects. 6.4 and 6.5. The first model is based on the existence of the undamaged (fictitious) configuration and on the deformation-like damage tensor, which is involved in the deformation gradient multiplicative decomposition into its parts. Here F d characterizes the passage from the undamaged stress free configuration to the damaged stress free configuration. The second model is proposed within the second order elasto-plasticity, involving a symmetric defect density tensor, which is a measure of non-metricity of the so-called plastic connection. We extended to finite deformation the relationships between the continuum theory of lattice defect and the non-Euclidian geometry that has been provided within the small strain formalism. The constitutive and evolution equations are derived to be compatible with the free energy imbalance principle, which has been reformulated by Cleja-Ţigoiu (Int J Fract 147:67–812 (2007); Int J Fract 166:61–75 (2010)), when the stress and stress momentum are considered. We assumed that the plastic flow and the development of the microvoids and microcracks are distinct irreversible mechanism during the deformation process.
Sanda Cleja-Ţigoiu
Chapter 7. Modelling the Portevin-Le Chatelier Effect—A Study on Plastic Instabilities and Pattern Formation
Abstract
An elastic-viscoplastic model of McCormick type incorporating dynamic strain ageing and negative strain-rate sensitivity is considered. A methodology for the identification of the unstable Portevin–Le Chatelier (PLC) range of strain-rates and mechanical parameters is considered by using a bifurcation analysis of spatial homogeneous processes. A critical condition on material parameters for the PLC effect is established. The loss of homogeneity and strain localization phenomena are investigated numerically for both constant strain-rate and constant stress-rate experiments. The sensitivity of the model to the mode of testing is analyzed. The influence of the testing machine is not taken into account by adding a machine equation, but by considering mixed stress- and strain-controlled boundary conditions. A discussion and comparison with existing models in literature is provided.
Cristian Făciu
Erratum to: Multiscale Modelling in Sheet Metal Forming
Dorel Banabic
Backmatter
Metadaten
Titel
Multiscale Modelling in Sheet Metal Forming
herausgegeben von
Dorel Banabic
Copyright-Jahr
2016
Electronic ISBN
978-3-319-44070-5
Print ISBN
978-3-319-44068-2
DOI
https://doi.org/10.1007/978-3-319-44070-5

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