Cracking analysis of fcc reactor structural metals based on a phenomenological constitutive model

The irradiation effect on the fracture toughness and the energy release rate in metallic materials leads to typical cracking behaviors in structural components of reactors. In this paper, the fracture toughness degradation mechanism and cracking behavior in irradiated face-centered cubic (fcc) metals are numerically analyzed using a newly developed phenomenological constitutive model. By characterizing the irradiation-induced plastic flow behavior through variations in the hardening modulus and taking into account the neutron-irradiation strain subjected to irradiation doses, a phenomenological constitutive model for irradiated fcc metals is constructed based on the framework of incremental plasticity theory. The constitutive model is validated as universally applicable over a wide irradiation range by comparing simulation results with experimental data. Furthermore, using the presented constitutive model, cracking simulations are conducted under various irradiation conditions. The numerical results show that the plastic zone near the crack tip decreases nonlinearly as the irradiation extent increases. Irradiation-induced degradation of fracture toughness is thoroughly interpreted through the influence mechanism of irradiation dose on the plastic zone near the crack tip. In addition, the irradiation effect on cracking is quantitatively analyzed by calculating the J -integral at the crack tip. The energy release rate during crack propagation increases logarithmically with increasing irradiation doses, indicating that irradiation accelerates cracking in fcc metals. As an application example, the presented constitutive model is utilized to estimate the onset condition for crack propagation in the fcc metal matrix. This study lays a foundation for investigating irradiation resistance performance and evaluating the failure of structural components in reactors.