Published: Jan 1970
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On the basis of a gust-load distribution, evaluated by applying level crossing-counting method, an 8-step program test and tests with a random sequence of stress cycles were performed. The results of these tests are compared with the results of tests with a random sequence of maxima and minima. The latter are based on a distribution of maxima and minima, which were derived from the gust-load distribution splitted in several stationary Gaussian processes. In further tests, ground-air-ground cycles were included in the study. Programmed and randomized flight-by-flight tests were compared.
The results of the study revealed that in the case of steady mean stress and the applied conditions program loading overestimates life by a factor of about 6. In case of flight-by-flight tests, however, the load-time history (either programmed or randomized) seem to be unimportant.
random processes, load (forces), fatigue (materials), digital techniques, computer programs, flight tests, crack propagation, tests, evaluation
Head, Deutsche Versuchsanstalt für Luft-und Raumfahrt, Institut für Festigkeit, Mulheim (Ruhr),