Johnson-Cook constitutive model and failure criterion for nuclear-grade stainless steel Z2CN18.10

Nuclear-grade stainless steel Z2CN18.10 is widely used in nuclear power plant piping systems. Its dynamic mechanical behavior under combined high strain rates and elevated temperatures is of great significance for assessing structural integrity under impact loads. To accurately characterize the mechanical behavior of Z2CN18.10 under dynamic loading, quasi-static and high-strain-rate tensile experiments were conducted using a universal electronic testing machine and a conventional split Hopkinson tension bar system. The stress-strain responses of the material were obtained within temperature ranges from ambient (25 ℃) up to 400 ℃ and strain rates from 10⁻³ to 10³ s⁻¹. To overcome the limitation of conventional Hopkinson bar apparatus in achieving large-strain loading, an electromagnetically driven bidirectional Hopkinson tension bar system was employed to measure the failure strain of the material under different stress triaxialities. Based on the experimental data, parameters for the Johnson-Cook constitutive model and failure criterion were fitted, and the validity of the model was verified through high-speed impact experiments using a gas gun. The results show that the differences between numerical simulations and experiments in terms of perforation diameter, peak strain, and support reaction force were 4.4%, 7.5%, and 2.3%, respectively, indicating good agreement. The established reliable dynamic constitutive model and failure criterion for Z2CN18.10 stainless steel provide an important methodological and data foundation for the impact-resistant design and safety assessment of nuclear power piping systems.