Modeling Creep-Fatigue Behavior of Mod.9Cr-1Mo Steel

Abstract This paper presents three models that were developed explicitly for predicting the creep-fatiguebehavior of Mod.9Cr-1Mo steel. The Cyclic Softening Model incorporated tensile strain hardening and creep deformation, and described the cyclic stress variation as a function of cycle number under hold-time creep-fatigue loading. The Stress Relaxation Model predicted the stress relaxation curve during the hold time of cyclic loading, based on the creep properties of the material. The Interactive Damage Rate Equation predicted the hold-time creep-fatigue life using a methodology, in which the key materials parameters were determined by the creep properties and continuous fatigue data. The model predictions captured the trends of creep-fatigue interaction in Mod.9Cr-1Mo steel, and were in good agreement with experimental data in the literature.