An Experimental Characterization of the Impedance and Spectral Content of Multistable Structural Responses during Dynamic Bifurcations

The ability to predict multistable structural dynamics challenges the development of future high-performance air vehicles that will be subjected to extreme multiphysics loads. To aid in the establishment of methodologies that characterize the response states of harmonically excited multistable structures, a catalog of empirical and practical evidence is necessary. Recent research has suggested that evolving aspects of mechanical impedance metrics may be correlated with measurable quantities, although their relation to bifurcations of the dynamic response remains incompletely understood. Motivated to begin establishing such knowledge base, this research seeks to construct a library of experimental evidence from which to draw generalized insights on the impedance- and spectral-changing trends of multistable structures undergoing severe nonlinear response due to harmonic loading. A connection between vanishing real and imaginary components of impedance and dynamic bifurcations is uncovered. In the process, a technique to forecast dynamic bifurcations is articulated, which utilizes mechanical impedance measurements in real-time to monitor the susceptibility of postbuckled structural components to undergo dynamic bifurcations. An examination of higher-order harmonics of the dynamic responses further illuminates the nearness to bifurcations and may help classify the precise response regime. Thus, by correlating the real-time impedance and spectral response with analytical predictions, a future tool may be established for condition monitoring and diagnosis.