FATIGUE LIVES OBTAINED IN RANDOM AND PROGRAM TESTS ON FULL-SCALE WING CENTER SECTIONS.
NATIONAL AERO- AND ASTRONAUTICAL RESEARCH INST AMSTERDAM (NETHERLANDS)
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Fatigue tests were conducted on eight full-scale wing center sections of the F-27 Friendship aircraft. The specimen consisted of the tension skin, including all stiffening elements. The remainder of the wing was replaced by a dummy structure. Two tests were carried out for each of the following load sequences 1 random load 2 programmed load 3 random load with ground-to -air cycles 4 programmed load including ground-to-air cycles. The random loading was based on a simulation of strain gage records obtained by flying in turbulent air. The primary aim of the investigation was to study the equivalence of random and programmed loadings. A comparison of the fatigue lives and the critical components indicated the following trends a Cracks were found in the same components for all tests. b The fatigue life under the programmed load was slightly longer than in the random load tests, both for tests without and with ground-to-air cycles. c The addition of ground-to-air cycles reduced the fatigue life to 50 or even less. For one fatigue-sensitive element sufficient data were available for a statistical evaluation this indicated that the scatter within one structure may be smaller than the variability between a number of identical structures. Author
- Transport Aircraft