[PDF] Widespread Fatigue Damage In Military Aircraft eBook

Author :
Publisher :
Page : 214 pages
File Size : 13,96 MB
Release : 1995
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ISBN :

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A structure potentially susceptible to Widespread Fatigue Damage (WFD) is defined by the Industry Committee on Widespread Fatigue Damage, as a structure which has the characteristics of similar features operating at similar stresses where structural capability could be affected by similar cracking. The well-publicized 1988 incident of the Aloha Airlines Boeing 737, which lost a large section of fuselage structure in flight, ushered in the era of research into ageing aircraft. This incident was caused by a collinear series of fatigue cracks which suddenly linked to form a single critical crack, leading to the catastrophic failure. At the time of the Aloha incident, a large number of relatively high-life military aircraft were in service, mainly in the roles of air transport, air-to-air refueling and maritime reconnaissance. Maintaining the structural integrity of these aircraft in prolonged service requires consideration to be given to inspections for detecting possible multiple damage in its various forms: 'Multi-site' damage (MSD) occurs mainly on neighbouring elements (lines of attachment holes, for example) or as a result of a fabrication surface damage (a long, continuous, scratch, for example). Their coalescence can lead to a sudden loss of residual strength. The concept of 'resistance to damage' implies structures which are able to tolerate the presence of cracked elements by ensuring that cracks are slowly propagated and to tolerate the presence of broken elements by providing load path redundancy. On this basis, the strength of the remaining undamaged structure must be sufficient to ensure safety in flight during a specified operating period. The role of Damage Tolerance is to assure structural integrity through in-service directed inspections of critical structures.

Author :
Publisher :
Page : 253 pages
File Size : 14,84 MB
Release : 1997
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The effect of corrosion and widespread fatigue damage (WFD) on the structural integrity of USAF aging aircraft could be detrimental to aircraft safety, readiness, and R & M (Reliability & Maintainability) costs. However, with the development and validation of appropriate structural life analysis tools and the supporting data, the effect of corrosion and WFD can be evaluated and therefore managed. But first, the supporting data will need to identify those structural elements which could cause a reduction in aircraft safety, readiness, or R & M when subject to corrosion or fatigue damage. The USAF aircraft fleets selected for consideration included the C/KC-135 Stratotanker, E-8C Joint STARS, C-9A/C Nightingale, C-130 Hercules, and C-5A/B Galaxy. The overall objective is to create a database, which is useful in identifying trends for the occurrence of corrosion and fatigue cracking damage to airframe Principal Structural Elements (PSEs). The database assembled under this effort contains individual records of inspection Reports and Repair Orders which have been obtained from standardized USAF damage and repair recording systems (such as OACIS, AIRS, REMIS, AND AFMC202) and from other USAF programs funded to collect specific airframe damage and repair records. This database is not intended to contain all the data, which might be used in a structural integrity evaluation, but it can be used to identify PSEs, which may need further consideration of their structural integrity capability. The trends developed provide real and repeatable evidence to assist in focusing improvement efforts where the largest gains can be made. The results from this project estimate the extent of corrosion and fatigue damage, which exists in the selected USAF aircraft systems. The Pareto trend format is used often to report the results as database record counts in decreasing order grouped by PSE type, location, and the defect type/severity.

Author : National Research Council
Publisher : National Academies Press
Page : 124 pages
File Size : 29,27 MB
Release : 1997-09-30
Category : Technology & Engineering
ISBN : 0309174473

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Many of the aircraft that form the backbone of the U.S. Air Force operational fleet are 25 years old or older. A few of these will be replaced with new aircraft, but many are expected to remain in service an additional 25 years or more. This book provides a strategy to address the technical needs and priorities associated with the Air Force's aging airframe structures. It includes a detailed summary of the structural status of the aging force, identification of key technical issues, recommendations for near-term engineering and management actions, and prioritized near-term and long-term research recommendations.

Author : Paul W. Tan
Publisher :
Page : 10 pages
File Size : 23,79 MB
Release : 2003
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ISBN :

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A methodology to assess the development of widespread fatigue damage (WFD) and its effect on the residual strength of aircraft structure has been developed. The three major components of the methodology are crack initiation, crack growth and linkup, and residual strength. The crack initiation methodology uses experimentally generated equivalent initial flaw size (EIFS) data and an analytical closure model to determine initial flaw sizes and distribution for multiple-site cracking. The crack-tip opening angle (CTOA) and the T* integral, and plastic zone touch (PZT) criteria were used to predict crack growth and linkup.

Author : Rhys Jones
Publisher : Butterworth-Heinemann
Page : 972 pages
File Size : 15,70 MB
Release : 2017-12-05
Category : Technology & Engineering
ISBN : 008100544X

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Aircraft Sustainment and Repair is a one-stop-shop for practitioners and researchers in the field of aircraft sustainment, adhesively bonded aircraft joints, bonded composites repairs, and the application of cold spray to military and civil aircraft. Outlining the state-of-the-art in aircraft sustainment, this book covers the use of quantitative fractography to determine the in-service crack length versus flight hours curve, the effect of intergranular cracking on structural integrity and the structural significance of corrosion. The book additionally illustrates the potential of composite repairs and SPD applications to metallic airframes. Covers corrosion damage assessment and management in aircraft structures Includes a key chapter on U.S. developments in the emerging field of supersonic particle deposition (SPD) Shows how to design and assess the potential benefits of both bonded composite repairs and SPD repairs to metallic aircraft structures to meet the damage tolerance requirements inherent in FAA ac 20-107b and the U.S. Joint Services

Author : National Aeronautics and Space Adm Nasa
Publisher : Independently Published
Page : 28 pages
File Size : 12,41 MB
Release : 2018-10-25
Category : Science
ISBN : 9781729175309

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NASA has developed a comprehensive analytical methodology for predicting the onset of widespread fatigue damage in fuselage structure. The determination of the number of flights and operational hours of aircraft service life that are related to the onset of widespread fatigue damage includes analyses for crack initiation, fatigue crack growth, and residual strength. Therefore, the computational capability required to predict analytically the onset of widespread fatigue damage must be able to represent a wide range of crack sizes from the material (microscale) level to the global structural-scale level. NASA studies indicate that the fatigue crack behavior in aircraft structure can be represented conveniently by the following three analysis scales: small three-dimensional cracks at the microscale level, through-the-thickness two-dimensional cracks at the local structural level, and long cracks at the global structural level. The computational requirements for each of these three analysis scales are described in this paper. Harris, Charles E. and Newman, James C., Jr. and Piascik, Robert S. and Starnes, James H., Jr. Langley Research Center RTOP 538-02-10-01

Author : Air Force Flight Dynamics Laboratory (U.S.)
Publisher :
Page : 924 pages
File Size : 39,79 MB
Release : 1971
Category : Airframes
ISBN :

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The document is comprised of papers presented at the Air Force Conference on Fatigue of Aircraft Structures and Materials, sponsored by the Air Force Flight Dynamics Laboratory (AFFDL) and the Air Force Materials Laboratory (AFML), Air Force Systems Command. The purpose of the Conference was to discuss technological advancements in fatigue and fracture theory. The Conference was comprised of ten technical sessions (including two panel discussions) entitled 'The Role of Materials in Structures'; 'Fundamentals I + II'; 'Criteria'; 'Fracture I + II'; 'Phenomena I + II'; 'Analysis'; 'Design and Service Experience'. A total of fifty-six technical papers were presented.