Large Amplitude Response of Complex Structures due to High Intensity Noise
Final rept. May-Aug 1978
OHIO STATE UNIV RESEARCH FOUNDATION COLUMBUS
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A problem of interest to the Air Force is the design of acoustically sound aircraft structural components. This is because sonic fatigue failures have resulted in unacceptable maintenance and inspection burdens associated with the operation of the aircraft. In some instances, sonic fatigue failures have resulted in major redesign efforts of structural components. Currently, the sonic fatigue design methods are based upon a combination of experimental and analytical techniques. The analytical methods are based on the linear or small deflection theory Sonic Fatigue Design Guide for Military Aircraft, AFFDL-TR- 74-112, for example. But, on the contrary, the test structural panels respond nonlinearly with large deflections at high intensity acoustic pressure levels. This large amplitude geometrical nonlinearity is the major factor that causes disagreement between the computed and the measured random responses. To improve the analytical design methods, large deflection or nonlinear structure theory must be employed in the analysis. This report presents a review of existing analytical and numerical methods on random excitation on nonlinear multi-degree- of-freedom systems, and an evaluation of these methods based on some realistic considerations from the point of view of their application to complex panel configurations of aircraft structure.