Non-saturated cyclic softening and uniaxial ratcheting of a high-strength steel: Experiments and viscoplastic constitutive modeling

The aim of the present investigation is to construct a constitutive model suitable for describing the cyclic behavior of 10Ni5CrMoV high-strength steel, which displays both cyclic softening and asymptotic ratcheting. Uniaixal tests of monotonic loading, symmetrical and asymmetrical strain cycling and stress controlled cyclic loading are conducted. Results reveal that the material exhibits non-saturated cyclic softening with combined nonlinear and linear softening rates, both isotropic and kinematic hardening are responsible for cyclic softening. A long period of steady-state ratcheting has been experimentally detected. Cyclic softening is found to have a considerable effect on the uniaxial ratcheting of the material. Significantly larger monotonic yield stress than that at cyclic loading is also observed. The dependence of cyclic softening on strain amplitude is revealed by a low-high sequence strain controlled cyclic test. Based on the experimental findings, a new constitutive model extended from Abdel-Karim-Ohno model has been constructed for 10Ni5CrMoV steel. The identification procedure of the material parameters is scrutinized critically by quantifying the contributions of the isotropic hardening and kinematic hardening on cyclic softening. Verification of the proposed model is achieved by simulating uniaxial strain and stress controlled cyclic loading tests. Fairly good modeling results are obtained. The superiority of the proposed model over other kinds of Ohno-Wang type models is also illustrated.