A modified low cycle fatigue Chaboche model for irradiation hardening behaviour of EUROFER97 at elevated temperatures

This study investigates the irradiation hardening mechanical behaviour of EUROFER97, a Reduced Activation Ferritic/Martensitic (RAFM) steel, using a modified Chaboche model within the temperature range of 250–350 °C. Structural materials for nuclear fusion reactors must maintain their performance under neutron irradiation. However, EUROFER97 faces challenges such as irradiation-induced hardening and embrittlement at irradiation temperatures below 350 °C, which lead to reduced ductility and toughness. This research incorporates an irradiation hardening factor into a modified Chaboche constitutive model to accurately simulate EUROFER97's behaviour under irradiation. A unified viscoplastic model is employed for finite element analysis, with variable parameters used to better represent the material's stress-strain evolution during cyclic loading and irradiation-induced hardening. Simulations are conducted using ABAQUS, with a UMAT subroutine developed to simulate fatigue, and a hybrid acceleration strategy is adopted to accelerate the calculation of different stages of Low Cycle Fatigue (LCF). Key findings demonstrate that the modified Chaboche model effectively predicts the irradiation hardening and cyclic softening behaviour of EUROFER97 under various irradiation doses and strain amplitudes. The model's predictions are in good agreement with experimental data, capturing the stress-strain hysteresis loops and irradiation-induced changes in mechanical properties, thereby validating its applicability not only to EUROFER97 but also to other nuclear structural materials, such as F82H ferritic/martensitic steel. The contribution of this study lies in refining the Chaboche model by incorporating irradiation effects, providing a robust tool for predicting the mechanical behaviour of structural materials under irradiation, which is crucial for the safety and design of fusion reactor components.