Study on the Johnson-Cook Constitutive Model and Failure Criterion for Nuclear-Class Stainless Steel Material Z2CN18.10

Nuclear-class stainless steel Z2CN18.10 is extensively used in nuclear power plant piping systems owing to its superior mechanical properties and corrosion resistance. Understanding its dynamic mechanical behavior under combined high-strain-rate and high-temperature conditions is essential for evaluating structural integrity under impact loads such as those caused by missile or pipe whip hazards. To accurately characterize the dynamic response of Z2CN18.10, systematic quasi-static and high-strain-rate tensile tests were conducted. Quasi-static testing was conducted utilizing an electronic universal testing machine, while high-rate tests were carried out with a conventional Split Hopkinson Tensile Bar (SHTB) system. These experiments captured full stress-strain responses across a temperature range from ambient (25°C) up to 400°C and strain rates varying from 10-3 to 103 s⁻¹. To address the limitation of conventional Hopkinson bars in achieving large plastic strains before fracture, an electromagnetically driven bidirectional Split Hopkinson Tension Bar was employed. This advanced setup enabled precise measurement of failure strain under different stress triaxiality conditions (0.3333~0.7388), providing crucial data for characterizing ductile damage evolution. Based on the comprehensive experimental results, the parameters for the Johnson-Cook (J-C) constitutive model, which accounts for strain hardening, strain rate sensitivity, and thermal softening effects, along with the J-C failure criterion, were carefully calibrated. The calibrated model was further validated through gas-gun high-speed impact tests that simulate high-velocity penetration scenarios. Numerical simulations using the calibrated model showed excellent agreement with experimental observations, with minimal deviations—only 4.4% in perforation diameter, 7.5% in peak strain, and 2.3% in peak support reaction force. a reliable and accurate dynamic constitutive model and failure criterion for Z2CN18.10 stainless steel are established, providing valuable insights and a solid database for the design and safety assessment of nuclear piping systems subjected to impact loading. The outcomes significantly enhance predictive capabilities in numerical simulations related to nuclear component safety and integrity. caused by missile or pipe whip hazards. To accurately characterize the dynamic response of Z2CN18.10, this study conducted systematic quasi-static and high-strain-rate tensile tests. Quasi-static testing was conducted utilizing an electronic universal testing machine., while high-rate tests were carried out with a conventional Split Hopkinson Tensile Bar (SHTB) system. These experiments captured full stress-strain responses across a temperature range from ambient (25°C) up to 400°C and strain rates varying from 10^-3 to 10³ s⁻¹. To address the limitation of conventional Hopkinson bars in achieving large plastic strains before fracture, an electromagnetically driven bidirectional Split Hopkinson Tension Bar was employed. This advanced setup enabled precise measurement of failure strain under different stress triaxiality conditions, providing crucial data for characterizing ductile damage evolution. Based on the comprehensive experimental results, the parameters for the Johnson-Cook (J-C) constitutive model, which accounts for strain hardening, strain rate sensitivity, and thermal softening effects, along with the J-C failure criterion, were carefully calibrated. The calibrated model was further validated through gas-gun flat plate impact tests that simulate high-velocity penetration scenarios. Numerical simulations using the calibrated model showed excellent agreement with experimental observations, with minimal deviations—only 4.4% in perforation diameter, 7.5% in peak strain, and 2.3% in peak support reaction force. This study establishes a reliable and accurate dynamic constitutive model and failure criterion for Z2CN18.10 stainless steel, providing valuable insights and a solid database for the design and safety assessment of nuclear piping systems subjected to impact loading. The outcomes significantly enhance predictive capabilities in numerical simulations related to nuclear component safety and integrity.