Modeling of scatter and size effect in ductile fracture: application to thermal embrittlement of duplex stainless steels

The aim of this work was to investigate the effect of specimen size and geo metry on ductile fracture of cast duplex stainless steels after thermal emb rittlement. Different specimen geometries, including smooth and notched bar s, Charpy and compact tension (CT) specimens, were tested using three diffe rent materials. These specimens were used to investigate both crack initiat ion and propagation. In all cases, a significant scatter was observed. Size effects were also evidenced using homothetic samples having the same geome try. Microstructural investigations have also shown that damage is highly h eterogeneous. In order to predict rupture, finite element models were used. The material was described using the Gurson model. In order to model size effects and sc atter, it was necessary to account for the distribution of damage nucleatio n rates which were experimentally measured by quantitative metallography. C omparison of experiments with simulations showed that the model can be appl ied to describe both crack initiation and propagation. In particular it can predict mean value and scatter observed on strain to failure (tensile bars ) and on initiation and propagation energies (Charpy and CT specimens). (C) 2000 Published by Elsevier Science Ltd.