Validating Global Structural Damping Models for Dynamic Analyses

Abstract

Finite Element (FE) models grow in terms of detail and complexity. They strive to provide a more precise mass and stiffness distribution in order to achieve better load prediction capabilities. However, they also need to include damping models to achieve better results for dynamic loads analyses. This is why experiments are usually carried out to quantify global damping ratios of the final structure and include them in the analytical model for further calculations. Yet, especially for large aerospace structures assembled from different substructures, the experimental determination of damping ratios for the assembled structure may be impossible or ineconomical. Therefore, a consistent approach to predict the damping properties of assembled structures is desirable. In this work, FE models of a laboratory test structure and its two substructures are built up. Modal tests are carried out on the substructures. On the basis of correlated substructure modal damping ratios, global proportional damping models are applied on substructure level in order to build proportional substructure damping matrices, construct a nonproportional, full structure damping matrix and thus predict the damping properties for the fully assembled structure. The approach is validated with the help of experimental results from a modal test on the fully assembled laboratory test structure. Because of the unsatisfactory reproduction of the substructure damping properties by the selected damping models and the outcome for the assembled structure in this work, an additional investigation on computational model updating of damping parameters on substructure level is carried out on a simulated plate.