Model Updating and Uncertainty Quantification of Geometrically Nonlinear Panel Subjected to Non-uniform Temperature Fields

Abstract

Thin structures comprising the skin panels of advanced aircraft will experience extreme thermal stresses as well as dynamic loads at hypersonic speeds, leading to highly nonlinear behaviors such as buckling. In order to determine whether a model correctly captures changes in the dynamics due to heating, the linearized natural frequencies can be compared between test and the FE model at a certain thermal state. This is considerably more difficult if the panel is subjected to localized heating. This work presents a case study in model updating for a non-uniformly heated, geometrically nonlinear panel and evaluates the effect of uncertainty. A curved panel was subjected to localized heating, and measurements of the temperature distributions and of the initial shape were mapped to the FE model and parameterized to use in model updating. The model was then updated for the baseline thermal state, after which the updated model was used to compute the linear natural frequencies and mode shapes with respect to varying temperature fields and those were compared with the experimental data, revealing that the modal properties are highly sensitive to the model’s design parameters. It proved difficult to find an exact correlation by deterministic model updating. The uncertainties in some of the design parameters were then evaluated using a Monte Carlo simulation. The results suggest that even modest uncertainties in the model parameters cause large changes in the natural frequencies, so that the uncertain model bounds the range of the measured natural frequencies.