Fast Identification and Characterization of Nonlinearities in Experimental Modal Analysis of Large Aircraft

Abstract

The vibration characteristics of large aircraft are investigated in so-called ground-vibration tests. The experimental determination of the vibration characteristics is referred to as experimental modal analysis, which is based on linear procedure. Nonlinearities are not investigated in detail in these tests. Nowadays, the consideration of nonlinearities in the aeroelastic stability certification process is becoming more and more important. If nonlinearities are considered in the test strategy, the experimental acquisition of the nonlinear vibration characteristics can be accelerated. The aeroelastic behaviour of highly flexible structures such as large aircraft cannot be sufficiently described on the basis of linear models. New and well-established methods for the detection of nonlinearities are shown and discussed in this paper with regard to their application during industrial large-scale testing. Some of the techniques are proposed for implementation into the existing ground-vibration testing strategy. A simple modal model is presented for the identification and characterization of nonlinearities and is used for the effective enhancement of the presented identification strategy.