In this study, the vibration characteristics of an airborne external store, originally designed using MIL-STD-810G reference profiles, were re-evaluated to support structural optimization based on in-flight measurements. Nonlinear contact boundary conditions among bomb rack unit hooks, store lugs, and sway braces were considered to overcome the limitations of conventional linear analysis. Vibration data were obtained from nine rotorcraft flight sorties with the store mounted on a pylon, and a power spectrum density (PSD) envelope with a +3 dB safety margin was derived. Analysis accuracy was improved by incorporating high kurtosis, a defining feature of rotorcraft vibration, into the fatigue damage evaluation. To address the limitations of linear finite element analysis caused by nonlinear contact behavior, experimental transmissibility functions for the pylon-to-store energy path were established. Critical resonances were identified using vibration response spectrum analysis, and fatigue damage spectrum analysis confirmed that the AL7075 structure ensures adequate fatigue life over 2500 hours. The results suggest that MIL-STD-810G profiles are overly conservative. The proposed tailored 4-h accelerated PSD achieved an approximately 35 % stress reduction, enabling weight optimization.
Park et al. (Wed,) studied this question.
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