Douglas Aging Aircraft Programs

McGrew, Jean A.; Hoggard, Amos W.

doi:10.4271/892206

Cited by 2 publications

(1 citation statement)

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“…This approach, known as "safe decompression", was validated experimentally by Boeing for suddenly injected cracks (e.g., from a thrown engine fan blade) of up to forty-inches in length. Although the details are different, a generally consistent approach is used by Douglas [3]. Indeed, several of the recent incidents have been of this type, but with large-scale crack propagation only taking place in one of them.…”

Section: Backmrund ])Iscllssionmentioning

confidence: 99%

Applications of Advanced Fracture Mechanics to Fuselage

Kanninen

O’Donoghue

Green

et al. 1991

Springer Series in Computational Mechanics

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Multi-site damage (MSD) in the form of cracking at rivet holes in lap splice joints has been identified as a serious threat to the integrity of coDJIDe1'Cial aircraft nearing their design life targets. Consequendy, to assure the safety of aircraft that have accumulated large numbers of flights. flight hours and years in service requires inspection procedures that are based on the possibility that MSD may be presenL For inspcc:tions of aircraft components to be properly focused on the defect sizes that are critical for structural integrity, fracture mechanics analyses arenccdcd. Thecmrcntmcthodsareessentiallythoseoflincarelasticfracturemechanics(LEFM) which are sttictly valid only for cracks that extend in a quasi-static manner under small-scale crack tip plasticity conditions. While LEFM is very likely to be appropriate for subcritical crack growth. quantifying the conditions for fracture instability and subsequent propagation may require advanced fracture mechanics techniques. The specific focus in this paper was to identify the conditions in which inelastic-dynamic effects occur in (1) the linking up oflocal damage in a lap splice joint to form a major crack, and (2) large-scale fuselage failure by a rapidly OCCun1ng fluid/structllrC interaction process. InggductionAn:ccntrash of akplanc accidents has drawn considerable public attention to what is now widely known as the aging aircraftissuc. A variety offailure modes has been expcricnccdin the accidents that have focused attention on this issue. However, undoubtedly because of the Aloha Airlines ain:raft canopy scpatation. large-scale fuselage fracture is likely the best known. This failure was abetted by the presence of wide-spread cracking along rows of rivet holes in the lap splice joints in a fuselage skin -a phenomenon generally called multi-site damage (MSD). Of greatest technical concern. the Aloha Airlines incident revealed that the crack arrest capability of the design can be defeated when MSD exists.Considering the great number of older aircraft that are presendy in service -indeed, to determine what "oldcr" really means -some type of quantitative examination is clearly mandated. While details may differ, all such approaches must conform to the "datnage tolerance" philosophy in which periodic proof tests and/or nondesU'UCtive inspections (NDI) are combined with fracture mechanics analyses for the rate of growth to criticality of the most seven: crack that wo~ go undetected. For most situations, ordinary linear elastic fracture mechanics (LEFM) will suffice for this purpose. However, the presence of MSD engenders a number of complications that might lie beyond the limits of LEFM. The objcctive of this paper is to quantify the role of inelastic and dynamic effects that are embodied in an advanced fracture mechanics approach.

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Section: Backmrund ])Iscllssionmentioning

confidence: 99%