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 to 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.


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    Title :

    Shape optimization of critical stiffener runouts for F-111 airframe life extension


    Contributors:
    Heller, M. (author) / McDonald, M. (author) / Burchill, M. (author) / Watters, K.C. (author)


    Publication date :

    2002


    Size :

    22 Seiten, 32 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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