DF: Ductile fracture
Minisymposium organized by
- P.-O. Bouchard, CEMEF, Centre de Mise en Forme, Mines-ParisTech, Sophia Antipolis, France
- J. M. A. César de Sá, University of Porto, Portugal
- R. H. J. Peerlings, TU Eindhoven, The Netherlands
Ductile fracture has been studied over the years at different scales. For metallic materials, ductile damage is the result of nucleation, growth and coalescence of micro voids at the micro scale. At the macro scale, these mechanisms induce a progressive softening of the material’s mechanical properties, finally leading to fracture. Many theoretical models and numerical approaches have been presented to study ductile fracture phenomena at both scales. However, due to the complexity of these phenomena, many theoretical and numerical issues still remain to be addressed.
The aim of this symposium is to make a step forward in the comprehension of the physical mechanisms of ductile damage under complex loading paths and to discuss the computational challenges associated to ductile damage, both at the micro-scale and at the macro-scale.
Special attention will be paid to:
- Ductile fracture micromechanisms: Recent advances in experimental observations enable a better understanding of ductile damage micromechanisms under different types of loadings. Based on these observations, new models are defined to simulate the stages of nucleation, growth and coalescence of microvoids. Interesting work also needs to be done on the finite element representation of microstructures, including grains and particles and their behaviour/evolution for large plastic strain applications.
- Influence of stress triaxiality ratio and Lode angle parameter on ductile fracture: It has been shown in the past that simplistic representations of damage growth were not suitable when dealing with complex loading conditions. This is the case for example for multi-stage forming processes, where the material can be submitted to multiaxial and non-monotonic strain paths as well as large plastic strain. Influences of stress triaxiality ratio and Lode angle on damage nucleation, growth and coalescence have to be studied further.
- Analysis and modelling of damage to fracture transition: When damage reaches a critical value, a macroscopic crack can initiate and propagate in the material. The transition from continuous damage mechanics to discrete fracture mechanics is still an issue both in terms of physical modeling and numerical representation of fracture initiation and propagation.
- Regularization techniques to deal with ductile damage localization issues: At the macroscopic scale, coupled damage models give rise to softening mechanical behaviour. From a numerical point of view, this softening can induce some spurious numerical dependencies such as damage localization or mesh sensitivity. Many different non local approaches have been proposed to circumvent this pathologic aspect. Typically those approaches require the use of length scale parameters whose physical meaning and theoretical justification is not always straightforward. Advances on these aspects and a thorough research and discussion on their evidence are still required.