Résumé
In irradiated polycrystalline uranium dioxide (UO2 ), the pressure generated at high temperatureby the noble gases in the intergranular bubbles as well as the thermomechanical stresses due totemperature gradients cause the fracture of the grain boundaries. In this study, starting from anatomistic identification of the fracture energy, one analyzes through mesocopic calculations thebehavior of grain boundaries under uniaxial tensile loading up to fracture. In these mesocopicalsimulations, a cohesive-volumetric approach using concepts of Frictional Cohesive Zone Models(FCZM) and numerical modeling methods based on Non-Smooth Contact Dynamics (NSCD)is employed to simulate grain boundary rupture with the presence of a void under uniaxialtensile loading. The associated computational code, called XPER (eXtended Finite Elementmethod and PERiodic homogenization), allows the analysis of fracture at grain boundaries.A parametric study on the void size and shape is conducted. Voids with sharp edges promotestress concentration, facilitating rupture initiation. The observed trends regarding the variationin void size are similar to the Griffith model, and the results align with experimental findings.