1. Introduction

Here, we are interested in a metallic structure subjected to thermomechanical stress. The aim is to determine criteria for the failure of this structure, representative of the two mechanisms encountered on certain steels:

• at low temperature, some metallic materials (such as tank steel) can behave like fragile materials by breaking suddenly by cleavage,

• At higher temperatures, the ductile tear occurs.

In contrast to the global approach, the Bordet and Rice-Tracey models presented here rely on the knowledge of mechanical fields in the most stressed areas in order to obtain a local failure criterion representative of the physical mechanisms involved (instability of cleavage microcracks or increase then coalescence of porosity).

The foundations of the Beremin model, which also makes it possible to model fragile fractures, are given in the documentation [R7.02.04].

Tips for using the Beremin and Bordet models are given in the documentation [U2.05.08].