Extending GTN model to viscoplasticity for describing ductile damage in irradiated F/M steels

Irradiation of Eurofer97, a reduced activation ferritic/martensitic steel used in fusion reactor applications, induces significant hardening, loss of uniform elongation (UE) and embrittlement. To estimate the maximum operating strain range of irradiated components beyond the loss of UE, a coupled deformation-ductile damage model at the component scale is proposed. This study extends the GTN ductile damage model to viscoplasticity with a simple formulation, integrating it into an existing finite strain viscoplastic model that combines kinematic hardening, isotropic softening, and irradiation hardening/softening. Therefore, the developed model captures the Bauschinger effect, finite deformation, and the irradiation-induced material changes contributing to reduction in fracture strain. Implemented in ABAQUS, the model is validated using tensile test data from both irradiated and unirradiated Eurofer97. A study on irradiation dose and initial triaxiality influence demonstrates the model’s consistent and reliable predictions.