Modeling of Stiffened Panels Using the Energy Finite Element Analysis

Stiffened panels are encountered in many engineering systems since the stiffeners comprise the mechanism which provides support and rigidity to the panel's skin. Either a mechanical excitation or an acoustic load can be applied on a stiffened panel creating vibration that is transmitted in all panel components. Mechanical excitation tends to be localized in nature, originating from operating machinery mounted on the panel, while the acoustic excitation tends to be distributed over the entire panel, since it typically originates from an external acoustic source which creates an acoustic field impinging on the entire panel. In the Energy Finite Element Analysis (EFEA) various degrees of fidelity are possible when modeling the response of a stiffened panel. In this paper, the theoretical background and the corresponding implications associated with each alternative modeling approach are presented first. Results are available in the literature (from the NASA Langley Research Center) describing modeling and correlation studies for an aluminum stiffened panel. In this paper EFEA models are developed for the NASA stiffened panel reflecting the alternative modeling techniques. The results obtained by this work are compared to the previously published test data, Statistical Energy Analysis (SEA) results, and EFEA results. The comparative analysis addresses the impact of the alternative modeling approaches to the observed correlation levels.