The influence of burr formation and feed rate on the fatigue life of drilled titanium and aluminium alloys used in aircraft manufacture

Following drilling, fatigue life trials were performed on as-drilled and deburred specimens made from Ti-6Al-4V, AA7010 and AA2024, with feed rates varied at 2 levels. Deburring dramatically increased the fatigue performance of the Ti-6Al-4V and AA7010 samples by 69% and 283% respectively, but there was no significant effect on the AA2024 alloy. Fractography showed failure initiated near the exit burrs in Ti-6Al-4V and AA7010 specimens but not in the AA2024 workpieces. Correlation (R2) of fatigue notch factor against the sum of entrance and exit burr height was 0.68 and 0.79 for Ti-6Al-4V and AA7010 respectively, compared to 0.54 for AA2024.