Thermal Loading on the Natural Frequencies of Postbuckled Clamped Circular Panels

Given a constrained slender structure and subject to thermal loading, that is, relative to ambient conditions and any support structure, a reduction in stiffness not only leads to buckling, but also has a strong effect on the natural frequencies of the system. One of the simplest structural forms is a thin circular panel, clamped around its perimeter, and the current paper focuses attention on such a system. A key aspect of this work is the extraction of sets of natural frequencies throughout the buckling process, with a primary focus on experimentally measured frequencies. Given the cyclically symmetric nature of the system, there are also some interesting observations concerning the changing vibration mode shapes as a function of thermal loading, and more clearly in the postbuckling regime. Another novel aspect of this research is an additional focus on the characterization of snap-through between postbuckled equilibrium configurations and its influence on the natural frequencies. That is, thermally buckled panels often possess multiple equilibrium configurations (bistability), with some characteristic transitions (both naturally occurring and forced) between them. Three panels are tested, consisting of two different materials (aluminum and brass) and two different thicknesses.