Phase Resonance Testing of Nonlinear Vibrating Structures
Modal testing and analysis is well-established for linear systems. The objective of this paper is to progress toward a practical experimental modal analysis methodology of nonlinear mechanical structures. In this context, nonlinear normal modes (NNMs) offer a solid theoretical and mathematical tool for interpreting a wide class of nonlinear dynamical phenomena, yet they have a clear and simple conceptual relation to the classical linear normal modes (LNMs). A nonlinear extension of force appropriation techniques is developed in this study in order to isolate one single NNM during the experiments, similarly to what is carried out for ground vibration testing. With the help of time-frequency analysis, NNM modal curves and their frequencies are then extracted from the time series. The proposed methodology is demonstrated using a simple numerical benchmark, which consists of a two-degree-offreedom system with a cubic spring.
KeywordsContinuous Wavelet Transform Nonlinear Structure Nonlinear Normal Mode Experimental Modal Analysis 2DOF System
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