A three-stage constitutive model for the creep behaviours of high-Cr steels at elevated temperatures

In this paper, a three-dimensional constitutive model is proposed to simulate the creep behaviours of high-Cr steels at elevated temperatures. In the model, the minimum creep rate and the average creep rupture time at different temperatures and stress levels are predicted by adopting two Larson-Miller parameters. The decrease of the creep rate during the primary creep stage is captured by introducing an internal variable representing the strain hardening effect. The material parameters of the model can be identified by using the conventional experimental results. Both the strain-and stress-driven algorithms are designed to solve the constitutive evolution equations. The response of high-Cr steels during the whole creep procedure can be predicted at a quantitative level by the current model. Further implementing the model into a finite element software, the global creep behaviours of high-Cr components under realistic loading conditions can be simulated.