Ratcheting and stress relaxation of SA333 Gr. 6 carbon steel samples under uniaxial multistep strain-controlled condition

In this present work, detail experimental characteristics of SA333 Gr. 6 carbon steel have been critically examined under uniaxial strain-controlled ratcheting and post ratchet strain cycling. Asymmetric cyclic plastic deformation, i.e., drifting of mean strain cycle by cycle is termed as strain-controlled ratcheting. Increment of mean strain induces additional hardening under strain-controlled ratcheting. Mean strain induced additional hardening which is primarily kinematic in nature. Also, the material exhibits mean stress relaxation behavior under strain-controlled post ratchet strain cycling. After certain accumulation of mean strain severe cyclic softening is observed on stress amplitude under uniaxial multistep post ratchet strain cycling. Cyclic softening on stress amplitude is primarily because of ratcheting damage. The proposed model incorporates ratcheting induced additional hardening under strain-controlled ratcheting and exhibits mean stress relaxation characteristics under strain-controlled post ratchet strain cycling through an internal variable of memory stress parameter to account for the effect of prior loading history. The proposed model is implemented in user subroutine UMAT of Finite Element software ABAQUS. The proposed model is validated through close correlation between simulation and experiments.