NASA Airframe Structural Integrity Program

Harris, Charles E.

doi:10.1007/978-3-642-84364-8_10

Cited by 14 publications

(5 citation statements)

References 7 publications

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“…In the L-T tests [7], the stable crack growth began in the interior, similar to the T-L test, as seen by the second and third crack front profiles shown in Fig. 4b.…”

Section: And Discussionsupporting

confidence: 61%

“…However, after about lmm of surface crack extension the crack front began to straighten, with the surface catching up to the interior. This reduction in the extent of tunneling corresponded to the onset of 45°slant crack growth [7]. Metallographicevaluationof boththe T-L andL-T fracture surfacesdid not show any significantdifferences;both demonstrated classicaldimpledruptureprofiles through the thicknessandalong the crackfront.…”

Section: And Discussionmentioning

confidence: 91%

“…Fracture tests were conducted on 2024-T3 aluminum alloy M(T) specimens in the T-L orientation, with comparisons made to similar tests conducted on specimens in the L-T orientation [7]. Surface crack growth measurements were made using an optical microscope.…”

Section: And Discussionmentioning

confidence: 99%

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Orientation Effects on the Measurement and Analysis of Critical CTOA in an Aluminum Alloy Sheet

Sutton

Dawicke

Newman

1995

Fracture Mechanics: 26th Volume

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Fracture tests were conducted on 76.2mm wide, 2.3mm thick middle crack tension (M(T)) specimens machined from 2024-T3 aluminum sheet. The specimens were tested in the T-L orientation and comparisons were made to similar tests conducted in the L-T orientation. Measurement of critical crack tip opening angle (CTOA), applied stress, and crack front shape were made as a function of crack extension. A two-dimensional, elastic-plastic finite element analysis was used to simulate the fracture behavior for both orientations. The results indicate that the T-L orientation had a 10% lower stress at fracture than similar tests conducted in the L-T orientation. Correspondingly, the critical CTOA in the T-L tests reached a constant value of 4.7° after 2–3mm of crack extension and the L-T tests reached a value of 6°. The fracture surface of the T-L specimens were observed to remain flat, while those of the L-T specimens transitioned to a 45° slant fracture after about 2–3mm of crack extension. The tunneling behavior of the two orientations also differed; the T-L specimens reached a deeply tunneled stabilized crack front shape, while the L-T specimens were observed to have only a small amount of tunneling once the crack began to grow on the 45° slant. The two-dimensional, elastic-plastic finite element analysis was able to simulate the fracture behavior for both the T-L and L-T orientations.

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“…In the L-T tests [7], the stable crack growth began in the interior, similar to the T-L test, as seen by the second and third crack front profiles shown in Fig. 4b.…”

Section: And Discussionsupporting

confidence: 61%

Section: And Discussionmentioning

confidence: 91%

See 1 more Smart Citation

Orientation Effects on the Measurement and Analysis of Critical CTOA in an Aluminum Alloy Sheet

Sutton

Dawicke

Newman

1995

Fracture Mechanics: 26th Volume

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“…Performance gains for metallic structures prior to the 1990s were primarily achieved through advances in aluminum alloy material properties. However, concern about the adequacy of understanding of damage tolerance and durability of metallic structure has risen during the past two decades [1].…”

Section: Introductionmentioning

confidence: 99%

Fracture Response Enhancement of Aluminum Using In-Situ Selective Reinforcement

Abada

Farley

Hyer

2006

47th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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A computer-based parametric study of the effect of reinforcement architectures on fracture response of aluminum compact-tension (CT) specimens is performed. Eleven different reinforcement architectures consisting of rectangular and triangular cross-section reinforcements were evaluated. Reinforced specimens produced between 13 and 28 percent higher fracture load than achieved with the unreinforced case. Reinforcements with blunt leading edges (rectangular reinforcements) exhibited superior performance relative to the triangular reinforcements with sharp leading edges. Relative to the rectangular reinforcements, the most important architectural feature was reinforcement thickness. At failure, the reinforcements carried between 58 and 85 percent of the load applied to the specimen, suggesting that there is considerable load transfer between the base material and the reinforcement.

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“…Assessment of residual strength of aircraft structures has been a focus since the launch of NASA's Airframe Structural Integrity Program (Harris, 1991), and several studies on mechanical properties of AA2198 base materials (BMs) with regard to fatigue (Cavaliere and de Santis, 2008;Alexopoulos et al, 2013;Le Jolu et al, 2015), fatigue crack propagation (Cavaliere and de Santis, 2008;Murray, 2010;Tavares et al, 2013;Kashaev et al, 2014) and resistance against crack extension (R-curve) (Steglich et al, 2010, Chen, 2011) have been carried out. There is a lack of available data concerning the R-curve behaviour of AA2198 welds.…”

mentioning
confidence: 99%

Fracture mechanical behaviour of laser beam-welded AA2198 butt joints and integral structures
Kashaev
¹
,
Riekehr
²
,
Erdmann
³

et al. 2015
International Journal of Structural Integrity
10
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Purpose – Composite materials and metallic structures already compete for the next generation of single-aisle aircraft. Despite the good mechanical properties of composite materials metallic structures offer challenging properties and high cost effectiveness via the automation in manufacturing, especially when metallic structures will be welded. In this domain, metallic aircraft structures will require weight savings of approximately 20 per cent to increase the efficiency and reduce the CO2 emission by the same amount. Laser beam welding of high-strength Al-Li alloy AA2198 represents a promising method of providing a breakthrough response to the challenges of lightweight design in aircraft applications. The key factor for the application of laser-welded AA2198 structures is the availability of reliable data for the assessment of their damage tolerance behaviour. The paper aims to discuss these issues. Design/methodology/approach – In the presented research, the mechanical properties concerning the quasi-static tensile and fracture toughness (R-curve) of laser beam-welded AA2198 butt joints are investigated. In the next step, a systematic analysis to clarify the deformation and fracture behaviour of the laser beam-welded AA2198 four-stringer panels is conducted. Findings – AA2198 offers better resistance against fracture than the well-known AA2024 alloy. It is possible to weld AA2198 with good results, and the welds also exhibit a higher fracture resistance than AA2024 base material (BM). Welded AA2198 four-stringer panels exhibit a residual strength behaviour superior to that of the flat BM panel. Originality/value – The present study is undertaken on the third-generation airframe-quality Al-Li alloy AA2198 with the main emphasis to investigate the mechanical fracture behaviour of AA2198 BMs, laser beam-welded joints and laser beam-welded integral structures. Studies investigating the damage tolerance of welded integral structures of Al-Li alloys are scarce.

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NASA Airframe Structural Integrity Program

Cited by 14 publications

References 7 publications

Orientation Effects on the Measurement and Analysis of Critical CTOA in an Aluminum Alloy Sheet

Orientation Effects on the Measurement and Analysis of Critical CTOA in an Aluminum Alloy Sheet

Fracture Response Enhancement of Aluminum Using In-Situ Selective Reinforcement

Fracture mechanical behaviour of laser beam-welded AA2198 butt joints and integral structures

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