Fracture Analysis Of Irradiated Metal Based On Crystal Plastic Finite Element Method

Fracture failure of metal materials under irradiation is very likely to cause major safety accidents in nuclear engineering.To explore the fracture performance of metal materials under irradiation is of great significance for the safe and stable operation of nuclear engineering and the research and development of nuclear structural materials.Neutron irradiation is the closest approach to the real situation of nuclear fission and fusion reactors.Neutron irradiation affects the microstructure of metal materials,and many macro-mechanical behaviors of metal materials are sensitive to microstructures,such as plastic deformation,creep,fatigue,and fracture.The crystal plastic finite element method combines the crystal plastic theory with the traditional finite element method,and simulates the plastic deformation process of the material at the grain scale according to the material constitutive relation,so as to realize the research on the influence of the microstructure on the macroscopic mechanical behavior of the material.Therefore,the crystal plastic finite element method has outstanding advantages when studying the problem of fracture of metallic materials under neutron irradiation.In this paper,the crystal plastic finite element method is used to simulate and analyze the fracture of metallic materials under neutron irradiation.The main work includes the following three aspects:(1)A method for fracture analysis of single crystal metal materials under neutron irradiation is presented,which can be used to study the fracture properties of single crystal metal materials under neutron irradiation and to calcula te the critical load of fracture failure.On the basis of the classical theoretical model of crystal plasticity,the irradiation hardening model and the multi-parameter slip rate expression are introduced to establish the theoretical model of crystal plast icity of single crystal metal under neutron irradiation.Based on the secondary development method of ABAQUS User Material Subroutine(UMAT),the finite element method of the crystal plasticity theoretical model is implemented.The fracture behavior of the FCC single crystal copper under neutron irradiation was simulated by the crystal plastic finite element method and the fracture analysis was carried out according to the simulation results.(2)A method for fracture analysis of polycrystalline metal materials under neutron irradiation is presented.The critical loads of fracture failure of polycrystalline metal materials with different average grain sizes under neutron irradiation can be calculated.Considering the effect of grain size,the Hall-Petch effect was introduced into the constitutive relation to establish the theoretical model of crystal plasticity of polycrystalline metals under neutron irradiation.Based on Voronoi method,parametric modeling of three-dimensional polycrystalline finite element models with different grain sizes was carried out.The fracture behavior of the FCC polycrystalline copper with three groups of different average grain sizes under neutron irradiation was simulated and the fracture analysis was carried out according to the simulation results.(3)An analytical method for crack propagation of metal materials under neutron irradiation is presented,which can simulate the whole crack propagation path of metal materials under neutron irradiation.The crack propagation process of metal materials under neutron irradiation is simulated by combining the crystal plastic finite element method and the extended finite element method.An ABAQUS user-defined GUI application was developed based on the equivalent integral region method to calculate the J-integral of the crack tip during crack propagation.The FCC single crystal copper was used as an example to simulate crack propagation under neutron irradiation.