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Lightweight spacecraft components such as reflectors are very sensitive to acoustic loading, and accurate prediction of peak stresses encountered in an acoustic test is critical to a successful design. A boundary element model (BEM) provides a very accurate means of representing the acoustic input into a finite element model (FEM) of the structure and has proven to be the method of choice for lightweight reflectors. Various aspects of accurate BEM modeling of acoustic input to a FEM of a lightweight reflector will be discussed. This includes choosing the portion of the structure that needs to be modeled to get correct boundary conditions and acoustic input, and also the modeling of the effect of a reverberant chamber on the acoustic response at low frequencies. Predictions will be compared with measured responses for both cases in order to illustrate the critical aspects of this modeling.

The perturbed boundary condition (PBC) model updating procedure has been developed to correct the finite element model [1]. The use of additional structural configurations adds more experimental information about the system and so better updating results can be expected. While it works well for simulated examples, practical limitations and additional requirements arise when it is used to update engineering structures. In this paper, the merits and the practical limitations of the techmques will be discussed in depth through the updating of a simulated system where the “measured” data is generated by computer and a real test structure where the experimentally measured data is noisy and distorted due to leakage. Useful suggestions and recommendations are drawn to guide the model updating of practical engineering structures.