Numerical simulation of the cold pilgering process of ODS tubes
Résumé
For new fast-neutron sodium-cooled GEN IV reactors, the candidate cladding materials for the very strong rates of combustion are the ferritic and martensitic ODS grades. Classically the cladding tube is cold formed by a sequence of cold pilger rolling passes with intermediate heat treatments. Within the framework of this numerical simulation study, the HPTR cold pilgering process is investigated. The model under development takes into account the complex kinematics of the process as well as the material constitutive behavior under cyclic elastic-plastic loadings. The use of numerical sensors to follow the deformation path of a volume element during the process allows estimating the nature and the amplitude of the cyclic deformations. The identification of the deformation path is the first step toward a better understanding of the critical conditions leading to damage and cracking. The material is highly textured and consequently mechanically anisotropic. The influence of the constitutive behavior on the deformation path is analyzed using two different plasticity criteria : Von Mises (isotropic), and Hill48 (anisotropic). Integration of a proper damage indicator into the proposed numerical model leads to the numerical optimization of the process in terms of maximum acceptable deformation before heat treatment, or process parameters (tools kinetics, dies profile, etc.).