Numerical Assessment of Fatigue Damage Evolution at the Crack tip in AA2099 Al–Li Alloy Sheet

Precipitate phase characteristics in Al–Li alloy sheet significantly influence damage evolution during fatigue crack propagation. To investigate the influence mechanisms, the present work establishes a cross-scale model that integrates the extended finite element method (XFEM) and the crystal plasticity finite element method (CPFEM) to elucidate the damage evolution at the crack tip. The results reveal that the T₁ phase facilitates the dislocation slip reversibility, with non-hardening slip retracting back to the crack tip, thereby reducing the cumulative damage. The accumulated shear strain could effectively predict the crack propagation paths. The planar slip effect of the δ′ phase significantly enhances the accumulated shear strain of the (1-11)[110] slip system, promoting single slip and resulting in a serrated propagation path. Conversely, the T₁ phase inhibits planar slip, enhancing the accumulated shear strain of multiple systems, and promoting multiple slip, leading to a relatively straight crack propagation path.