Contribution to the analysis of the fracture of polycrystalline mechanical components

This Habilitation to conduct researches covers about twenty years of activity dedicated to the analysis of the breakage of polycrystalline mechanical components. Three main fields of continuous and cracked media mechanics have been studied in depth: limit analysis, stress intensities, and J-integral. A more modest contribution is the use of the coupled simulation of behavior and damage. These studies concern mesh techniques, but also the modeling of crack components and the calculation of the parameters describing the intensity of the applied loading. The present works have been carried out fairly systematically keeping a strong link with the microstructural characteristics of the polycrystalline material. The essential contribution of the fractographic studies and the description of the behavior of sub-granular scale materials is highlighted. The work carried out underlines the possible limits in the approximation of simulation and microstructural analyzes. However, these disciplines remain complementary in order to establish a valid modeling of the fracture conditions of polycrystalline mechanical components. Studies on the fatigue of the materials resulting from these different contributions are evoked. In this context, the development of simulation codes for fatigue crack propagation, including under complex loading, is briefly described. During the last fifteen years, the activity of the author has been dedicated to the zirconium alloys used for the realization of fuel rods in nuclear pressurized water reactors. The fuel sheath is the first barrier in maintaining the safety of the reactors. Different accident scenarios are envisaged to delimit the acceptable conditions of use of these components. Corrosion and hydriding, affecting the mechanical strength of the sheath during its operation are described in detail. Modeling and interpretation on the breakage of the components for transport accidents or reactivity injection are then detailed