Possibilities for reducing fatigue-test time for supersonic-transport materials and struc¬tures were studied in tests with simulated flight-by-flight loading. In order to determine whether short-time tests were feasible, the results of accelerated tests (2 sec per flight) were compared with the results of real-time tests (96 min per flight). The effects of design mean stress, the stress range for ground-air-ground cycles, simulated thermal stress, the number of stress cycles in each flight, and salt corrosion were studied. The flight-by-flight stress sequences were applied to notched sheet specimens of Ti-8Al-lMo-lV and Ti-6A1-4V titanium alloys. A linear cumulative-damage analysis accounted for large changes in stress range of the simu¬lated flights but did not account for the differences between real-time and accelerated tests. The fatigue lives from accelerated tests were generally within a factor of two of the lives from real-time tests;thus, within the scope of the investigation, accelerated testing-seems feasible.
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