PhD opportunities

PROVIDED - Modelling of the irradiation effect on fracture toughness of structural hardening aluminum alloys Application to 6061-T6

Thesis proposal

Area of expertiseMechanics
Doctoral SchoolSystems Engineering, Materials, Mechanics, Energy
SupervisorM. Jacques BESSON
Research unitCentre of materials
Starting dateOctober 1st 2019
Keywordsfracture mechanics, ductile rupture, Finished elements, material mechanics, metallurgy
AbstractThe aluminum alloy 6061-T6 is known for its neutron transparency, its high conductivity, its good resistance to corrosion, its good mechanical properties at unirradiated state, and its residual ductility after irradiation.
Previous studies showed the essential role of the hardening and strain hardening ability of this alloy on the evolution of fracture toughness, resistance to ductile tearing and appearance of instabilities. Moreover, the irradiation modifies its microstructure at nanometrical scale, thereby modifying its mechanical behavior, without modifying the coarse precipitates leading to damaging.

The main goal of the study will be to use modelling to test this scenario, refining our current comprehension of the mechanisms. This study will synthetize previous works which enabled to (i) characterize and model the fracture toughness at unirradiated state using local approach to fracture based on the alloy microstructure, (ii) characterize the evolutions of microstructure after irradiation, taking interest now in fracture toughness simulation of the irradiated alloy.

In order to refine our comprehension of the ductile damaging mechanisms piloting the fracture and to predict the evolution of fracture toughness with fluence and spectrum, we need to model the effect of irradiation on these mechanisms and to establish a behavior model taking into account the effect of fluence. These physical tools, using mechanical data available in the literature and at the CEA, will be extrapolated to other non-experimentally tested fluence and spectrum conditions and can be used eventually to predict the cracking resistance of an irradiated structure such as a pressurized vessel.

This study takes place in the project of development of the future reactor of experimental irradiation RJH (Racteur Jules Horowitz), built on the site of the CEA Cadarache to follow the reactor OSIRIS (CEA Saclay). The 6061-T6 aluminum alloy was selected to manufacture the vessel, internal structures (rack) and external structures (reflector) of the RJH. In operation, the vessel will be subjected to a high neutron irradiation. This study therefore strengthens the justification file of the design of the vessel and internal structures of the RJH. It defends the safety (behavior with a crack as a function of the fluence) and end-of-life (residual fracture toughness at final fluence) aspects of the vessel, with a view toward its instruction buy the French Safety Authority.
ProfileEngineer and / or Master of Science - Good level of general and scientific culture. Good level of knowledge of French (B2 level in french is required) and English. (B2 level in english is required) Good analytical, synthesis, innovation and communication skills. Qualities of adaptability and creativity. Teaching skills. Motivation for research activity. Coherent professional project.
FundingContrat de recherche
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