Session: 02-05-01: Experimental Studies in Structural Dynamics

Paper Number: 151151

151151 - Experiments on the Effect of Thermal Loading on the Natural Frequencies of Clamped Circular Panels 

Applying an increase in thermal loading to a restrained structural member inevitably leads to compressive axial loads and buckling. Given a constrained slender structure and subject to thermal loading, i.e., relative to ambient conditions and any support structure, a reduction in stiffness not only leads to buckling, but also has a profound 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 direct comparison between experimentally measured frequencies and the outcome of numerical simulations via finite element analysis (ANSYS), and a limited amount of available analytic results. Given the axi-symmetric nature of the system, there are also some interesting observations concerning the changing mode shapes as a function of thermal loading. This a sensitive system in which small geometric imperfections can have a profound effect on critical buckling temperatures and naturel frequencies.

In the post-buckling regime, there exist a variety of possible equilibrium configurations: a highly nonlinear environment. Under perturbation the system may exhibit sudden (snaps) between states, and these abrupt changes are also apparent in the tracking of natural frequencies. Furthermore, these subtle effects manifest themselves in the forced problem – i.e., when the structure is excited, resulting in highly nonlinear dynamic behavior, and this has clear implications for fatigue life.

Three panels are tested, consisting of two differential materials (aluminum and brass) and two different thicknesses. Digital image Correlation (DIC) and thermal Imaging (FLIR) are used to extract full-field data.

Presenting Author: Charles Cervi Duke University

Presenting Author Biography: Charles 'Chip' Cervi is a PhD student in the department of Mechanical Engineering at Duke University in North Carolina. He graduated with a BS degree from NC State University in Raleigh.