Premium
Shape optimization of critical stiffener runouts for F‐111 airframe life extension
Author(s) -
Heller M.,
Mcdonald M.,
Burchill M.,
Watters K. C.
Publication year - 2002
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1046/j.8756-758x.2001.00.x
Subject(s) - airframe , rework , structural engineering , finite element method , reduction (mathematics) , shape optimization , engineering , work (physics) , stress (linguistics) , service life , extension (predicate logic) , wing , mathematics , mechanical engineering , computer science , geometry , aerospace engineering , linguistics , philosophy , programming language , embedded system
Optimal rework shapes for the most critical stiffener runout fatigue locations in the F‐111 wing pivot fitting have been determined using a recently developed finite‐element‐based gradient‐less shape optimization procedure. The resulting precise free‐form shapes render the local notch stress distributions near uniform and typically provide a 30–40% reduction in peak elastic stresses as compared to the current rework shapes that exist for aircraft in service with the Royal Australian Air Force. The present numerical results are also consistent with recent preliminary experimental results, and a significant program of further validation testing is envisaged. Hence it is expected that the stress reductions predicted in the present work will be sufficient to provide a basis for extending inspection intervals by at least a factor of two; from 500 to 1000 h. Implementation of such an extension to the F‐111 fleet in service with the Royal Australian Air Force would provide a very significant maintenance cost saving. The anticipated reduction in local crack growth rates would also allow achievement of the planned withdrawal date for the aircraft.