Assessment of prior fatigue damage and a new approach to predict remanent creep rupture of P92 steel

The quantitative assessment of prior fatigue damage plays a critical role in predicting the remanent creep life of as-service high-temperature components. However, the creep prediction models widely used in engineering show inherent limitations in remanent creep life prediction. In this study, under the framework of continuum damage mechanics, different types of damage variables are proposed and introduced into the four conventional creep life models to evaluate their capabilities to capture prior fatigue-effected creep life. Results show that four creep life models with tensile elongation-based damage variable all give more accurate predictions of creep life than the models coupled with other damage variables irrespective of prior low cycle fatigue and creep-fatigue damage. It is remarkable that the tensile elongation-based damage variable can be easily obtained by low-cost tensile tests. Additionally, comparisons of prediction ability among different creep models illustrate that Wilshire model incorporated with tensile elongation-based damage variable is considered as the best approach to assess the remanent creep life after various cyclic loadings, which will enrich the existing creep life design by considering prior fatigue damage.