École Nationale Supérieure de
Techniques Avancées

Abstract

The work of the thesis concerns the fine modeling of the thermomechanical and metallurgical behavior of steels in order to determine the residual mechanical state of the structures during welding or heat treatment operations. For these cases, difficulties mainly arise in the modeling of the solid-solid phase transformations as well as in the modeling of the mechanical behavior of the multiphasic material. Within an original theoretical framework - generalized standard materials with internal constraints – we proposed models for the behavior of multiphasic material in which the individual mechanical behavior of each phase is supposed to be known and the macroscopic behavior is then obtained using a Reuss model. It is necessary to mention that each phase can present a specific mechanical behavior (plastic or viscoplastic) and the effect of the TRIP - Transformation Induced Plasticity - can be taken into account, which constitutes the originality of the thesis. The models have been implemented into the numerical code COMSOL-Multiphysics and an experimental test presenting similar phenomena as those encountered during welding or heat treatment operations has been simulated. Comparisons between numerical and experimental results show the performance as well as the flexibility of our approach for the simulation of thermomechanical and metallurgical behavior of steels during welding or heat treatment operations.