Temperature rate dependent modeling of thermal ratcheting behavior

Abstract

Material behavior under cyclic thermal load is highly nonlinear and requires the understanding of theories of deformation mechanics to perform calculations not only for life estimation but also to ensure safe functionality of the industrial components. The nonlinear cyclic behavior due to cyclic thermal load, as in case of the main vessel of Sodium cooled Fast Reactors (SFR), results into thermal ratcheting strain. Excessive thermal ratcheting strain is one of the critical failure modes of the main vessel of SFR. The accuracy of the thermal ratcheting strain prediction depends on the choice of constitutive model and numerical integration method. The present work discusses experimental and a numerical method employing a simplified semiimplicit integration procedure for predicting the thermal ratcheting behavior. Further, it is demonstrated that there is essential need of considering temperature rate dependence while predicting thermal ratcheting strain. It is also observed that the mode of deformation of the thin cylindrical specimen of SS 316 L material changed with the change in loading methods and the proposed constitutive model estimated the thermo-mechanical behavior appropriately.