Mesoscale study of fatigue damage evolution of polycrystalline Al alloy based on crystal plasticity finite element method coupled with continuum damage mechanics

A finite element model, combined with a damage accumulation method, was developed to explore the mesoscale effects of microstructure on the evolution of low-cycle fatigue damage in AA 2024-T3 aluminum alloy. In this model, the maximum shear strain of the slip systems was computed as the damage criterion using crystal plasticity (CP) theory combined with continuum damage mechanics (CDM), the slip strength is related to the evolution of dislocation density, and the nonlinear kinematic hardening rule was used to capture the cyclic response. This constitutive model was capable of quantifying the local fatigue damage in 3D microstructural applied to the Voronoi polycrystals like the AA2024 Al alloy. The results show that grains with high Schmid factors usually suffer more severe damage than those with lower Schmid factors, while grains with lower Schmid factors mainly suffer damage at grain boundaries. The proposed constitutive model demonstrates the ability to capture the fatigue damage evolution of polycrystalline metal.