Interrogating the Configuration Space of Slender Structures

Abstract

This dissertation examines the postbuckled behavior of several different slender structures of varying complexity. In the postbuckled regime, each of these systems typically contain multiple equilibria, and under external loading possess the ability to transition between them. Characterizing this ability to switch between equilibria provides information on how robust the system is to external disturbances. As demonstrated in this work, this testing can often be done non-destructively, allowing for subcritical testing and analysis while still providing a great deal of information on the system.The chapters of this dissertation are ordered in a sequential manner of the complexity of the system. It begins with a simple beam and symmetric frame in a quasi-static test where the means of snap-through are characterized via end-moment actuation. Next, thin cylindrical shells with varying amplitudes of prescribed imperfections, thanks to 3D printing, are then subjected to axial compression for buckling analysis. Buckled, clamped circular panels are then interrogated to examine the equilibrium configurations. The combination of lateral probing and digital image correlation allowed the postbuckled landscape to be described. The same clamped circular panels are then subjected to relatively uniform thermal loading, where the deformation and change of natural frequencies are recorded as a function of temperature. Next, several thin rectangular panels incorporating a single spanwise rib stiffener were subjected to lateral probing to characterize the effect of the stiffener on the structural response. The same panels were then subjected to localized heating centered on the stiffener in which the postbuckling response is tracked and analyzed as the panels cool. Lastly, we return to the buckled, clamped circular panels. Two panels are subjected to various harmonic loading cases to capture the effect of the intensity of the loading on the panels' response in a thoroughly dynamic environment. Low amplitude oscillations about one equilibrium as well as large amplitude (nonlinear) vibrations resulting in snap-through between equilibria was captured.The majority of the experiments found in this work relied on advanced test equipment such as digital image correlation, thermal imaging, and vibrometers. Full-field data was acquired for the test articles, enhancing the data analysis that followed the experimentation. This dissertation primarily consists of experimental work with some comparisons to theory and finite element analysis.