Hardening parameters for modelling of CuCrZr and OFHC copper under cyclic loadings

Heat sink materials are used in nuclear applications for the construction of high heat flux components that can experience high temperature and high stress-strain conditions. The operations of these components are verified by numerical simulations that require the knowledge of the material modeling parameters. This paper deals with the determination of the material hardening parameters by carrying out FE analyses reproducing experimental testing conditions and results. The hardening parameters are treated as optimization variables in an optimization process that includes the FE simulations. The process minimizes a total error calculated comparing the hysteresis loops obtained by finite element analyses with experimental data of the cyclic stress-strain curves. Two hardening models have been considered to verify the matching of the parameters, both parametric in temperature: the first is a multi-linear kinematic hardening model to be used to simulate material hardening at stable hysteresis loops (for fatigue verifications); the second is the Chaboche's nonlinear hardening model that simulates non-symmetric hysteresis loops (for ratcheting and shakedown analyses). The materials considered for the characterizations are CuCrZr alloy and OFHC copper that are typical heat sink materials in nuclear fusion applications. The parameters presented in this paper have been used with hardening models to simulate numerically the thermomechanical behavior of ITER components operating in a wide range of temperatures (from 20 up to 300/500 °C for OFHC copper/CuCrZr alloy) and under cyclic loadings such as fatigue, ratcheting, and cold work treatments.