Local adaptive refinement method for the fracture of heterogenous materials

International audienceIn order to anticipate problems with aging nuclear power plants, the French ’Institutde Radioprotection et de Sûreté Nucléaire’ (IRSN) studies microstructural evolution ofconcrete (confinement structures) and of metallic components (reactor vessel, vesselwall, steam generator). The issues linked to the aging of these materials can be studiedthrough micromechanical methods based on the Finite Element numerical method. Inthis case, very fine meshes have to be used to take into account heterogeneities at thescale of the structure. A solution to reduce the associated computational costs is toperform local adaptiv mesh refinement involving refinement criteria which depend onthe studied physics.The refinement method used in this study is called ’CHARMS’ (Conforming HierarchicalRefinement MethodS) and is based on the refinement/unrefinement of the basisfunctions rather than the refinement of the finite elements and thus allows nonconformities[1]. These nonconformities are geometrical and not linked to spatial discretization :the approximation spaces remain H1-conform.Combining a local refinement criteria as critical value of the Von-Mises equivalentstress to the CHARMS method enables to perform refinement where heterogeneitieslinked to the chosen criteria are the most marked. Namely in the case of heterogenousmaterial this method is able to capture the local heterogeneity of the stress field betweentwo phases. An application to numerical concrete loaded in traction will be presentedshowing the local mesh refinement around aggregates and microstructures