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

摘要

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 ar_(ECS) (equivalent crack depth + aspect ratio) vs. ar_(cri) (critical pit depth * aspect ratio) are best correlated with correlation coefficient of 0.9, while the best correlated parameters for multi-crack initiations are ar_(ECS) (equivalent crack depth * aspect ratio) vs. r_(cri) (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.