A dislocation-based cyclic polycrystalline visco-plastic constitutive model for ratchetting of metals with face-centered cubic crystal structure

In the framework of crystal plasticity, a dislocation-based cyclic polycrystalline visco-plastic constitutive model is proposed to describe the ratchetting of the metals with a face-centered cubic (FCC) crystal structure. A new rate-dependent flow rule considering the thermal activation energy of dislocation slipping is developed, and a dislocation-based Armstrong-Frederick non-linear kinematic hardening rule is introduced to provide a better prediction to the ratchetting. The isotropic hardening associated with the short-ranged interactions of dislocations is represented by the evolution of critical shear stress in each slip system. Comparing the prediction with corresponding experimental results, it is shown that the uniaxial and multiaxial ratchetting of polycrystalline 316L stainless steel are reasonably described by the proposed model. The dependence of the intra-granular ratchetting on the crystallographic orientation of grains can be also reflected by the model.