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A Review of Australian Investigations on Aeronautical Fatigue during the Period April 1985 to March 1987.

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Structures technical memo.,

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The previous Australian ICAF review, referred to damage tolerance assessment work on the RAAF Mirage fleet. Since that time strain data from flight tests and ground calibrations have been analysed and this has led to the conclusion that structural control points in the rear fuselage and from fuselage are not stressed sufficiently highly to require detailed damage tolerance assessment. The Swiss fatigue test has been completed with the exception of the teardown inspection of some parts of the airframe. These include the fin which is thought to contain a crack at the main spart root. Crack growth calculations for damage tolerance assessment have been concerned with control points in the wing and fuselage frame 26. The Wheeler crack growth model has been successfully validated against crack growth data from ARL tests on component simulation specimens, and also against data from cracks generated in the wing during the Swiss fatigue test. However attempts to validate the model against Swiss crack growth data from frame 26 were unsuccessful. Predicted crack growth rates from the model using the best estimate of local strin response based on existing information were much slower than those measured on test. For this reason the inspection intervals calculated by the model for frame 26 need careful interpretation. This is under consideration at present.

Subject Categories:

  • Mechanics
  • Aircraft

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