Analysis of the effects of exfoliation corrosion on the fatigue behaviour of the 2024-T351 aluminium alloy using the fatigue damage map

The concept of the Fatigue Damage Map (FDM) is implemented to quantify the effects of exfoliation corrosion damage on the fatigue behaviour of the 2024-T351 aluminium alloy. This is achieved by using extensive experimental data involving tensile, fracture toughness, fatigue as well as fatigue crack growth tests on pre-exfoliated 2024-T351 specimens. The analysis suggests that exfoliation exposure leads to an increase in accelerated crack growth stage (Stage III) at the expense of Stage II (long crack growth). It also suggests that the transition from Stage I crack growth (short crack) to Stage II for the same stress level occurs at smaller crack lengths for the exfoliated material. Furthermore, stress intensity range values for onset of crack growth rate acceleration (Stage III) obtained from the experimental results for the pre-corroded specimens are in accordance with the results of the FDM analysis. The outcome of the analysis, demonstrates that the a priori negligence of the corrosion effect in structural integrity analyses of aged aircraft components may lead to significant overestimation of the damage tolerance ability of the structure.