Acoustic-induced random vibration analysis for spacecraft using wavenumber expression of joint acceptance

Abstract

The on-board components mounted on the structural panel of spacecraft are exposed to a severe random vibration environment, mainly induced by the acoustic excitation of the panel structure due to the large acoustic noise from the launch vehicle. To verify the components' resistance against the vibrational environment, random vibration tests of the components are generally performed at the excitation level based on vibroacoustic prediction. In order to consider the prediction uncertainty, there actually needs to add a margin, which often poses an excess of design and testing. JAXA has been involved with predicting wide frequency band vibro-acoustic behavior of the structural panel using SEA (Statistical Energy Analysis), in which we have to add margin to take into account spatial and frequency bandwidth uncertainties. These kinds of uncertainty margin may result in over conservative margin and causes costly over conservative design. To reduce the over conservative margin in SEA method, in this paper, a wavenumber expression of joint acceptance method calculated by fast Fourier transform approach on finite element model parameter of panel, i.e., mode frequency and mode shape is proposed. The proposed method is applied to two structural panels of actual spacecraft and compared with acoustic test results. It is shown by comparison with the test result of an actual panel that the proposed method achieved less conservative prediction in each individual component mounting location rather than enveloping every mounting location that SEA calculates.

Keywords

• acoustic
• random vibration
• spacecraft
• joint acceptance
• wavenumber transform
• fast fourier transform
• diffused acoustic field