Quantitative description between pre-fatigue damage and residual tensile properties of P92 steel

The alteration of material tensile properties is inevitable after material subjects to irreversible damage. This paper is devoted to quantify the influence of pre-fatigue damage on the residual tensile properties of P92 steel. Various pre-fatigue tests followed by uniaxial tensile tests are conducted at 650 °C. Results indicate that higher strain amplitude of pre-fatigue loading leads to reduction in residual yield stress and ultimate tensile stress (UTS). In addition, the evolution of yield stress and UTS in terms of pre-fatigue lifetime fraction shows two stages, namely initial rapid degradation stage and linear decreasing stage. The microstructure observation manifests that the growth of martensite lath width and the decline of dislocation density during pre-fatigue loadings contribute to the degradation of subsequent tensile strength. However, the reduction in dislocation density plays a dominant role. Furthermore, a pre-fatigue damage definition is proposed. The variations of residual yield stress and UTS can be described linearly with respect to the defined pre-fatigue damage. The newly proposed linear relationships are convenient for practical application.