INVESTIGATION OF THE REPRESENTATION OF AIRCRAFT SERVICE LOADINGS INFATIGUE TESTS
LOCKHEED AIRCRAFT CORP BURBANK CA
Pagination or Media Count:
An investigation was carried out of the effectiveness in fatigue tests of practical representations of aircraft service loadings. The investigation required the development of test apparatus capable of applying typical random loading histories. Using this equipment random gust loadings, military maneuver loadings, ground loadings, and composites of flight and ground loadings were applied. The results obtained were used to evaluate the adequacy of ordered, cyclic loading representations of the random loadings. The evaluations indicate that spectra of cyclic loadings based on simple mean crossing peak counts of service loading records can be directly employed in tests in which the maximum values of applied stress are moderately high. In tests where lower peak stresses are generated, the test lives may provide an unconservative estimate of service life. The results obtained in composite loading tests indicate that the cumulative effect of flight loadings, ground loadings, and ground to air transitions is nonlinear. However, in one set of tests representing the service conditions in the wing root region of conventional transport aircraft, adequate simulations of the effect of composite random loadings were obtained.
- Military Aircraft Operations