EXPERIMENTAL DETAILS OF TESTING A FULL-SCALE STRUCTURE WITH RANDOM AND PROGRAMMED FATIGUE LOAD SEQUENCES.
NATIONAL AERO- AND ASTRONAUTICAL RESEARCH INST AMSTERDAM (NETHERLANDS)
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For an investigation on the equivalence of random and programmed fatigue loads, eight full-scale wing center sections were tested. The report describes the fatigue machine developed for this purpose and some testing experience. Load monitoring of the hydraulic machine occurs by comparing a feed-back signal from a load cell with the output of a selected Wheatstone circuit with an adjustable potentiometer. There are 32 circuits which can be selected by a digital tape reader in any arbitrary sequence. In this way a random sequence of 32 load levels can be applied. The hydraulic and the electronic parts are described in some detail. In eight fatigue tests a good reliability and accuracy were obtained. During the fatigue tests the inspections for cracks were made visually and with X-ray equipment. Visual inspections were made when the test was running, in view of the increased sensitivity. The results of the X-ray method for small cracks were very sensitive for the mean load in the structure. Useful results were obtained. Author
- Transport Aircraft