Continuum models for ductile fracture accurately model onset of ductile tearing thanks to their stress triaxiality dependent formulations. Nevertheless, these models are subject to localization and convergence problems that hinder large crack propagation prediction. This paper presents a method to switch from a continuum mechanics model to a cohesive zone maintaining the mechanical energy. This is obtained thanks to a careful identification of the cohesive law whose computation is based on two points: The thermodynamical definition of the cohesive model and the assumption that, for a given problem, the plastic work during localization must be the same if modelled with a regularized continuum model or with introduction of an equivalent cohesive zone. The cohesive discontinuity is introduced in the framework of the eXtended Finite Element Method developed in CAST3M Finite Element code. This strategy permits to use the continuum model as long as it is the most appropriate and to introduce cohesive zone segments without energy loss. Moreover it solves numerical difficulties associated with the local vision of fracture. The performance of the proposed solution is illustrated on the Rousselier model for which a consistent cohesive law is identified. Results of fracture tests prediction on a CT specimen are compared with those obtained with the conventional Rousselier continuum mechanics formulation.

This content is only available via PDF.
You do not currently have access to this content.