Study of Rotational Kinematic Hardening Model: A General Plasticity Formula and Model Implement

Theories of the rotational kinematic hardening model are introduced in detail. This model is used to predict soil behaviors under large stress reversals by incorporating the rotation and intersection of isotropic hardening yield surfaces in principal stress space. During the monotonic loading, the model behaves the same as isotropic hardening model, but once stress reversals occurs, new kinematic yield surfaces will generate, then these yield surfaces evolve (e.g. rotate, shrink, expand, vanish etc.) obeying the rotational kinematic hardening rule in the process of loading. A general plasticity formula of rotated yield surface or plastic potential surface in the principal stress space is given in this research, which is the basis of the rotational kinematic hardening model. It is also a very integral part to design logical procedures to determine the load mode of soil element during surfaces’ evolution. New logical procedures developed by this paper have been successfully used within the framework of Lade-Kim model, test results and model predictions showed a good consistency in stress reversal triaxial tests using loose Santa Monica beach sand. Source codes of logical procedures to implement the rotational kinematic hardening model within the framework of Lade-Kim model are provided at the end of this paper to give readers a further understanding.