Application of viscoplasticity theory based on overstress (VBO) to high temperature cyclic deformation of 316FR steel

The viscoplasticity theory based on overstress (VBO) has been employed to model the uniaxial cyclic deformation of 316FR steel at high temperature. The experiments show that the stress strain response is rate independent in monotonic tension or the initial stage of cyclic straining, while the observed cyclic strain hardening is rate dependent. Also, the subsequent holding of strain results in a particular stress relaxation. These interesting deformation behaviors relating rate effects cannot be well reproduced by the conventional viscoplasticity theory. In the present paper extensions of VBO are introduced to reproduce these behaviors. The first extension admits a rate independent asymptotic solution. The second one produces the time (rate) dependent cyclic hardening. Good agreement is found between the experimental data and the numerical simulations-by the present model.