Crystal plasticity modeling of ratchetting in FCC alloys

Abstract

Ratchetting is the progressive, unidirectional accumulation of plastic strain during asymmetric stress cycling with nonzero mean stress. Modeling ratchetting is challenging, especially under complex cyclic loading conditions. Most existing constitutive models rely on phenomenological back stress formulations to characterize ratchetting responses, but they are only loosely connected to underlying physical mechanisms. This work develops a microstructure-sensitive crystal plasticity (MS-CP) model for ratchetting in face-centered cubic (FCC) alloys, applied to Alloy 600 (A600) and 304L stainless steel (SS). The model incorporates back stress evolution for slip systems, driven by both deformation-induced dislocation substructures and precipitate–dislocation interactions. The simulated monotonic and ratchetting responses at room and elevated temperatures are validated against experimental stress–strain data. Results highlight the strengthening effects of dislocation substructures in both alloys and of precipitates in A600, as well as the role of substructure evolution in ratchetting responses. This MS-CP model provides a physically grounded framework for modeling in FCC alloys under complex cyclic loading, supporting improved life predictions for components in service.