Some Aspects of Using the Random Decrement Technique for Nonlinear Systems

Abstract

The random decrement (RD) technique can be used to analyze the response signal from a system that has amplitude dependent modal parameters. The implementation of RD for this purpose is usually done by simply applying the technique at multiple amplitudes in the measured response signal. Modal parameters are then estimated based on RD signatures using well known time domain modal parameter estimation methods. This analysis procedure originates from the invention of the RD technique, and is described by several studies in the literature. However, the RD technique is developed for linear systems, and caution must be exercised when applying it to nonlinear systems. In this study, several aspects of applying of the RD technique on signals exhibiting nonlinear behavior are addressed. The principle of superposition does not apply for a nonlinear system. This means the averaging process in RD can yield corrupted results. The benefit of a sufficiently high sampling rate is described.