Date of Award
Doctor of Philosophy (PhD)
Mechanical & Aerospace Engineering
Howard F. Wolfe
Robert L. Ash
In stochastic structural dynamics, the majority of analyses have dealt with linear structures under stationary, Gaussian, and band-limited white noise excitations. Although these simplifying assumptions may be justified, in many processes experimental data have shown quite frequently the non-stationary and non-Gaussian characteristics of the loads. An efficient finite element modal formulation has recently been developed to extend the analysis to nonlinear structural responses. Laminated plate theory and von Karman large displacement relations are used to derive the nonlinear equations of motion for an arbitrarily laminated composite panel subjected to combined acoustic and thermal loads. The nonlinear equations of motion in structural node degrees of freedom are then transformed to a set of coupled nonlinear equations in truncated modal coordinates with rather small degrees of freedom. Recorded B-1B flight acoustic pressure fluctuations have shown the non-white power spectral density (PSD) characteristics. This work presents for the first time the nonlinear large amplitude response and fatigue life estimation of arbitrary laminated composite panels subjected to non-white pressure fluctuations with or without a high thermal environment. The Palmgrem-Miner theory is combined with the rainflow counting cycles method in time domain, and with transformed Gaussian models in the frequency domain, to estimate the panel fatigue life.
Equivalent band-limited White Noise Sound Pressure Level excitations (EWSPL), which have the same acoustic power within the bandwidth as the B-1B flight data, are generated. Nonlinear response and fatigue life are predicted for the identical panels subjected to EWSPL. Monte Carlo numerical simulation is used for the analysis of the EWSPL. Results show that the flight data with non-white PSD give higher stress characteristics and shorter fatigue life than the corresponding EWSPL.
"Nonlinear Response and Fatigue Estimation of Surface Panels to White and Non-White Gaussian Random Excitations"
(2001). Doctor of Philosophy (PhD), Dissertation, Mechanical & Aerospace Engineering, Old Dominion University, DOI: 10.25777/ppwa-n911