Local mechanical fields simulation: application to low alloy steels

The aim of this study is to take into account the effect of the plasticity mechanisms on the ductile-brittle transition in low alloy steels constituent the PWR reactors vessels. A crystalline plasticity model which describes the temperature effect on the behaviour has been implemented in a framework of great transformations. The mechanical and microstructural characterizations have allowed to determine several parameters, the others have then been identified by an inverse method from tensile mechanical tests. Polycrystalline aggregates simulations have been carried out at imposed triaxiality. The study of local heterogeneities show that the main stress distributions can be modelled by a distribution of extreme values of first specie (Gumbel) and that the parameters of this distribution can be easily described as a function of σmises and T. This approach will allow later on to introduce the effect of these heterogeneities in a local approach criteria of rupture. (O.M.)