Abstract:

Spacecraft suffer severe acoustic environments in the course of launching along with launch vehicles. Acoustic tests should be done to check up whether the spacecraft work well while suffering acoustic environments. Response properties of structural vibrations during acoustic tests for spacecraft should be considered in the structural strength design. Moreover, they are important foundations for specifying the random vibration test conditions of the spacecraft equipment mounted on the structural boards. Therefore, it is necessary to predict the structural responses due to acoustic loads in the preliminary stage of spacecraft development. In this paper, a finite element model of a spacecraft structure is built using the commercial finite element analysis software MSC.Patran and MSC.Nastran. The sound pressure level spectrum of acoustic loads is transformed to the power spectrum density of fluctuating pressure. And then, the random vibration responses of the spacecraft structure under the acoustic loads are analyzed using the modal method. The simulation results are compared with the acoustic test results. In the simulation analysis, the effects of the damping ratio model and the fluid added mass are studied. The research shows that: using an empirical damping ratio model that the damping ratio decreases with the rising of the frequency can do a better response prediction for the medium-high frequency properties as well as for the total root mean square results; further using the virtual mass method to consider the fluid added mass effect can do a better response prediction for the power spectrum density results. The proposed simulation method in the article is convenient for modeling and efficient for computation, which is appropriate for the response prediction of structural vibrations in spacecraft acoustic tests in the preliminary stage of spacecraft development.

Key words: acoustic tests, random vibrations, modal damping, virtual mass method, response prediction