In the nuclear field, the integrity of components must be ensured throughout their operating life, even in the event of an accident. The demand for justification of component resistance to the risk of sudden rupture is growing, and is being applied to a wide range of piping lines and equipment. The demonstration principle consists in showing that, even in the presence of a defect, the equipment is capable of withstanding the loads it is likely to be subjected to.
Particular attention is paid to brittle fracture by cleavage, because of its unstable and catastrophic nature, which immediately leads to the ruin of the component. Brittle fracture is sensitive to the level of plasticity and triaxiality at the crack tip, which explains the beneficial structural effect often observed on real components compared to laboratory specimens. The industrial challenge is to better understand the role of plasticity in relation to microtexture on brittle fracture, in order to improve current prediction criteria.

In the course of this thesis, the brittle fracture toughness of a ferritic steel will be evaluated after various types of mechanical pre-strain. By the end of the thesis, the candidate will have acquired solid skills in mechanical testing, microscopic analysis and numerical simulation. The work will be carried out between the LISN laboratory of the CEA and the materials center of the Ecole des Mines de Paris.