Understanding the small creep-fatigue crack growth mechanism of polycrystalline alloy based on crystal plasticity and extended finite element method

[Display omitted] •A small creep-fatigue crack growth model is established based on the combination of CPFEM and XFEM.•The criterion for creep-fatigue crack growth is proposed based on accumulated energy dissipation and shear strain.•Effects of grain orientation and constraint on creep-fatigue crack growth behavior is investigated. The multifarious nature of small crack growth at the micro-scale necessitates the use of advanced modeling methods. In this work, small creep-fatigue crack growth behavior is investigated based on the combination of crystal plasticity finite element method (CPFEM) and extended finite element method (XFEM). A creep-fatigue crack growth indicator parameter (CFCGIP) is developed to predict creep-fatigue crack path and growth rate with the aid of total accumulated energy dissipation and accumulated shear strain. Results show that the small creep-fatigue crack growth rate can be predicted accurately by comparing experimental data. Moreover, the combined effects of constraint condition and grain orientation on the small creep-fatigue crack growth behavior are studied by adopting the developed CFCGIP. Under low constraint conditions, the creep-fatigue crack growth rate is dominated by the grain orientation, accompanying with significant fluctuation. With the increase in constraint condition, the dominated role of the creep-fatigue crack growth rate is identified as constraint condition.