Modelling creep-fatigue behaviours using a modified combined kinematic and isotropic hardening model considering the damage accumulation

Abstract

The low cycle fatigue and low cycle fatigue-creep behaviours of P92 steel with strain-control mode and fully inverse loading waveforms at the temperature of 630 °C were investigated. A typical cyclic softening behaviour of P92 steel was observed. As the hold time was introduced at the tensile peak and compressive valley strains, the failure cycle was reduced and the stress reduction became more obvious with the increasing hold time because of the improvement in creep deformation. Moreover, a modified combined kinematic and isotropic hardening model by introducing a non-linear interaction damage accumulation constitutive model was proposed to capture the loop stress-strain behaviour until fracture and predict the failure life as the applied strain amplitudes and duration periods changed. The validation results showed that the accelerated cyclic softening and the greatly reduced failure cycle as the duration periods prolonged under the low cycle fatigue-creep interaction conditions were well described by the modified model.