A New NASA Handbook presents recommended procedures for the preliminary and final design of equipment items exposed to various dynamic loads, including random vibration excitations.1 For the final design when the geometric details of the equipment items have been largely determined, finite element method (FEM) and statistical energy analysis (SEA) procedures can be employed to predict the maximum stresses in equipment items due to random vibration excitations at their mounting points. In the preliminary design phase, however, more approximate prediction techniques are often needed, as summarized in the Handbook. The purpose of this paper is to detail the rationale behind these preliminary procedures. Included are simple techniques to predict a maximum instantaneous stress during a short duration vibration environment and fatigue damage during a long-duration vibration environment, based only upon estimates for the frequency and damping ratio of the first significant resonance of the equipment.

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