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

Abstract

The aim of this work was to investigate the effect of specimen size and geometry on ductile fracture of cast duplex stainless steels after thermal embrittlement. Different specimen geometries, including smooth and notched bars, Charpy and compact tension (CT) specimens, were tested using three different materials. These specimens were used to investigate both crack initiation and propagation. In all cases, a significant scatter was observed. Size effects were also evidenced using homothetic samples having the same geometry. Microstructural investigations have also shown that damage is highly heterogeneous. 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 scatter, it was necessary to account for the distribution of damage nucleation rates which were experimentally measured by quantitative metallography. Comparison of experiments with simulations showed that the model can be applied 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).