An internal variable dependent constitutive cyclic plastic material description including ratcheting calibrated for AISI 316L

The purpose of this work is to provide a reduced complexity constitutive model capable of accurately reproducing the material response of stainless steels under conditions of thermal stress-induced deformation occurring in the primary cooling circuit of a light water nuclear reactor. The proposed approach consists of a Chaboche-type material description, modified to allow the kinematic hardening parameters to vary as a function of a set of internal variables. The methodology implemented to calibrate the model using low cycle fatigue and strain-controlled ratcheting experiments performed on a stainless steel of grade AISI 316L is presented in detail. The improvement provided by the internal variable constitutive model is evaluated by a comparison with simulations carried out by means of an unmodified Chaboche description and with experimental data for strain-controlled, stress-controlled and thermo-mechanical low cycle fatigue tests.