Smart materials for low-carbon applications
The topic of this thesis focuses on the design of smart materials for low-carbon applications, with an emphasis on metallic additive manufacturing. This technology has revolutionized industrial production methods by enabling the creation of complex, lightweight parts while ensuring increased precision and flexibility. This is particularly relevant in demanding sectors such as aerospace, automotive, and nuclear industries, where reliability is crucial. By integrating optical sensors into metallic structures through additive manufacturing processes, it becomes possible to perform real-time monitoring of critical parameters such as stress, temperature, and radiation doses. This enhances the safety and efficiency of operational and maintenance activities. The thesis aims to address the challenges related to the monitoring and control of infrastructure conditions, ensuring continuous monitoring of structures and precise control of environmental parameters. Additionally, the study examines the durability of materials and how embedded sensors can function in hostile environments. Finally, this research aspires to develop solutions for effective and secure remediation and decommissioning processes.
Experimental characterization and numerical simulation of brittle fracture of intergranular oxides : Application to Irradiation-Assisted Stress Corrosion Cracking
Metal alloys used in industrial applications can form oxide layers in the presence of a corrosive environment. These oxides may be uniformly distributed on the surface and/or localized at the grain boundaries. In the latter case, the oxidized grain boundaries may experience brittle fracture under mechanical loading, potentially leading to intergranular cracking of the material. This mechanism is, for example, a possible scenario for the failure of austenitic stainless steel bolts used in the internals structure of Pressurized Water Reactors (PWRs). Under the effect of mechanical loading,
neutron irradiation and the presence of a corrosive environment, these bolts fail through a phenomenon known as irradiation-assisted stress corrosion cracking. To model this phenomenon, we need to determine the fracture properties of intergranular oxides, and to take into account the coupling between cracking, oxidation and irradiation. In this thesis, experimental and numerical work will be combined. Firstly numerical simulations based on the variational approach to fracture approach will be assessed in order to design micro-beam micromechanics experiments aimed at reliably determining the fracture properties of oxides, and also to study the couplings between cracking, oxidation and irradiation. In particular, the cracking-oxidation coupling that prefigures the transition between initiation and propagation will be investigated in detail. These experiments will then be carried out on model and industry-relevant steels, and interpreted using numerical simulations. Finally, all the results obtained in this work will be incorporated into simulations of polycrystalline aggregates, in order to assess the possibility of quantitatively predicting intergranular cracking in the context of irradiation-assisted stress corrosion.