Study of high-temperature uniaxial low cyclic fatigue and creep-fatigue behavior of P92 steel using a unified viscoplastic constitutive model

In this study, within the framework of the unified viscoplastic cyclic constitutive theory, a cyclic constitutive model is developed based on the modified Chaboche nonlinear kinematic hardening rule. The proposed model improves the prediction of stress relaxation and relaxation stress decay behavior of P92 steel with cycling through the flow rule of hyperbolic sine and static recovery term coupled with accumulative plastic strain and introduces the plastic strain range memory effect to better describe the cyclic softening characteristics of P92 steel. The proposed model is written into the user subroutine of finite element software ABAQUS. Strain-controlled low-cycle fatigue (LCF) and creep-fatigue interaction behavior simulations are performed for the ferritic-martensitic stainless steel P92 at different temperatures and different mechanical strain ranges, respectively. Moreover, a preliminary prediction of the LCF behavior of P92 steel under non-isothermal conditions is provided. By comparing with the experimental results, it can be found that the proposed modified model can provide positive simulation results.