CRACK PROPAGATION AND RESIDUAL STRENGTH OF 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 Fokker F.27 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 sequencies 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 crack propagation data indicated the following trends a crack propagation was slightly higher under a randomly varying load than under a programmed load sequence, 6 addition of the ground-to-air cycles increased crack propagation rates by an amount of about 50. As for the residual static strength of the structure in the presence of cracks the following remarks can be made a if cracks are short the structure behaves like an unstiffened panel, b for long cracks the stringers become effective in raising the residual strength. Author
- Transport Aircraft