A study of fatigue variability in aluminium alloy 7050-T7451

• An investigation into the material fatigue scatter in AA7050 plate was completed.
• Two failure locations on eight full-scale fatigue tests were considered.
• For monolithic aircraft structures, the level of fatigue scatter is location dependent.

This paper describes an investigation to determine the scatter in fatigue performance of aluminium alloy 7050-T7451 plate as used in a fighter aircraft. The results for two failure locations on eight full-scale fatigue tests of near identical modern monolithic airframe sections, as well as over 150 low stress concentration fatigue coupons that were tested at a number of stress levels were considered. Fatigue scatter was quantified in terms of the standard deviation of log10 fatigue lives. It appears that even for monolithic aircraft structures, the level of fatigue scatter is location dependent. Also, the results of the investigation indicated that the fatigue lives at mirrored locations on monolithic parts may not be independent of one another.