Multiscale modelling strategy for predicting fatigue lives and limits of steels based on a generalised evaluation method of grain boundaries effects

•Multiscale modelling strategy for predicting fatigue lives and limits of steels was proposed.•Strategy is applicable to both low-grade ferrite and high-grade bainite steels.•Macroscopic FEA, microstructure, and crack growth models were integrated.•Predicted results by the strategy was compared with experiments using three types of steels.•The results demonstrated the validity of the proposed multiscale modelling strategy. Multiscale modelling strategy for predicting fatigue lives and limits of steels is proposed based on a generalised method for evaluating grain boundaries’ (GBs) effects on fatigue crack growth. The proposed strategy is a modification of our previous works that extends the applicability from only low-grade ferrite steels to high-grade bainite steels. A microstructure model was developed considering distances between GBs and misorientations between adjacent grains. The strategy was validated by comparison with experiments using two ferrite-pearlite and one bainite steels; results indicate the strategy predicted fatigue lives and limits of steels with microstructures from coarse ferrite to fine bainite grains.