Magnitude Equivalence of Random Loads and Superposition with Transient Excitations

摘要

Methods to predict design loads in spacecraft payloads when combination of transient and random loads is important were studied. A closed form probabilistic expression which describes the statistical distribution of the magnitude equivalence was developed, and was verified through computer simulations and experiments. The presently used and the developed method were compared using recorded vibration time histories from STS-flights. The results indicate that the presently used methods produce design loads which correspond to risks of failure of typically 1% to 2%, and higher. Commonly used safety factors (1.2 to 1.5) however in most cases reduce the risk to less than 0.135%. It is recommended that the developed probabilistic method is included in the design procedures, or that presently used methods are revised.