FE modelling of bainitic steels using crystal plasticity

International audienceModels classically used to describe the probability of brittle fracture in nuclear power plants are written on a macroscale. Physical phenomena are not naturally captured by this type of approach, so that the application of the models far from their identification domain (temperature history, loading path) may become questionable. To improve the quality of the prediction of resistance and life time, microstructural information, describing the heterogeneous character of the material and its deformation mechanisms has to be taken into consideration. The purpose of the paper is to propose a model able to describe local stress and strain fields in 16MND5 bainitic steel. These data will then be used as critical variables for multiscale failure models. The microstructure of 16MND5 steel is made of bainitic packets coming from former austenitic grains, which are not randomly oriented. Knowing the macroscopic stress is thus not sufficient to describe the stress-strain state in ferrite. An accurate model must take into account the actual microstructure, in order to provide realistic local stress and strain fields. After providing some observations and the analysis of the bainitic microstructure, the paper shows a quantitative model of the morphology and the crystallography, then a finite element analysis involving crystal plasticity