Equivalent crack size model for pre-corrosion fatigue life prediction of aluminum alloy 7075-T6

•Fatigue crack initiates from a single pit or pit cluster at the central hole.•For single-crack cases arECS vs. arcri is best correlated with coefficient of 0.9.•For multi-crack cases arECS vs. rcri is best correlated with coefficient of 0.69.•ECS models are developed with the best relevant metrics arECS ∼ arcri and arECS ∼ rcri.•Npre predicted with ECS models agree well with Nexp with the error factor of 1.6.

Corrosion damage can significantly reduce the service life of aluminum alloy structures and endanger the structural integrity of aircraft. Here, aiming at center-hole sheet specimens of aluminum alloy 7075-T6, uniaxial fatigue tests and post-fracture analysis are performed to investigate the effect of corrosion pits on the pre-corrosion fatigue behavior. Then the best correlated parameters between corrosion pits and equivalent cracks are identified through Pearson correlation analysis. It is found that for single-crack initiations arECS (equivalent crack depth ∗ aspect ratio) vs. arcri (critical pit depth ∗ aspect ratio) are best correlated with correlation coefficient of 0.9, while the best correlated parameters for multi-crack initiations are arECS (equivalent crack depth ∗ aspect ratio) vs. rcri (aspect ratio) with correlation coefficient of 0.69. Equivalent crack size (ECS) models are correspondingly developed with these best correlated parameters for single- and multi-crack initiations, respectively. The pre-corrosion fatigue lives predicted with our models agree well with the experimental results and the maximum error factor is about 1.6.