Probability modelling and statistical analysis of damage in the lower wing skins of two retired B-707 aircraft

• Published in: Fatigue & fracture of engineering materials & structures 2001-08, Vol.24 (8), p.523-535
• Main Authors: Harlow, D. G., Wei, R. P.
• Format: Article
• Language: English
• Subjects: ageing aircraft; aluminium alloy; Applied sciences; corrosion fatigue crack growth; Exact sciences and technology; Fatigue; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; multiple site damage; pitting corrosion; probability of occurrence; tear-down data
• ISSN: 8756-758X; 1460-2695
• DOI: 10.1046/j.1460-2695.2001.00402.x

A plausible mechanistically based probability model for localized pitting corrosion and subsequent fatigue crack nucleation and growth is used to analyse tear‐down inspection data from two retired B‐707 aircraft that had been in commercial service for about 24 and 30 years. Sections of the left‐hand lower wing skins from these aircraft had been previously disassembled and inspected optically at 20× magnification. The inspections were augmented by metallographic examinations for the lower time aircraft. The evolution of damage in the fastener holes is estimated by using reasonable values for the localized corrosion and fatigue crack growth rates, statistically estimated from laboratory data. The primary loading, assumed to be the mean design load, is considered to be from ground–air–ground wing bending cycles, augmented by ‘average’ gust loading, only. The encouraging agreement between the estimated probability of occurrence and the observed distribution of multiple hole–wall cracks attests to the efficacy of the approach and its relevancy to airworthiness assessment and fleet life management.