Modelling of creep and plasticity deformation considering creep damage and kinematic hardening

This study addresses creep behavior under constant load with the evolution of damage and plastic deformation by load change. A creep strain rate equation with one damage variable is adopted. Two kinematic hardening models related to time-independent plasticity and viscoplasticity, respectively, are incorporated. Combining the creep equation and kinematic hardening theory, two models are proposed: a creep-plasticity model and a nonunified viscoplasticity model. Experiment data for Al 5083 and AISI type 316H are used to verify the utility of the proposed models. Due to the creep part with damage, both models precisely predict the creep strain curve and the rupture time and strain. However, the creep-plasticity model fails to describe the first-stage creep and strain rate sensitivity in monotonic tensile testing that can be captured with the nonunified viscoplasticity model. Finally, the parameter determination is discussed.