The application of an internal state variable model to the viscoplastic behavior of irradiated ASTM 304L stainless steel

Neutron irradiation of metals results in decreased fracture toughness, decreased ductility, increased yield strength and increased ductile-to-brittle transition temperature. Designers use the most limiting material properties throughout the reactor vessel lifetime to determine acceptable safety margins. To reduce analysis conservatism, a new model is proposed based on an internal state variable approach for the plastic behavior of unirradiated ductile materials to support its use for analyzing irradiated materials. The proposed modeling addresses low temperature irradiation of 304L stainless steel, and predicts uniaxial tensile test data of irradiated experimental specimens. The model was implemented as a user-defined material subroutine (UMAT) in the finite element software ABAQUS. Results are compared between the unirradiated and irradiated specimens subjected to tension tests.

► An internal state variable approach is used to predict the plastic behavior of irradiated metals.
► The model predicts uniaxial tensile test data for irradiated 304L stainless steel.
► The model is implemented as a user-defined material subroutine in the finite element code ABAQUS.
► Results are compared for the unirradiated and irradiated specimens loaded in uniaxial tension.