9 April 2010 Dynamics characterization and health monitoring of membrane structures by time-frequency analysis
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Membrane dynamics is often nonlinear and nonstationary because of geometric nonlinearity induced by high local flexibility, non-uniform pre-tension, light weight, dynamic coupling with surrounding air, wave propagation, supportinduced nonlinearity, and others. Hence, dynamics characterization and health monitoring of membrane structures require advanced time-frequency analysis, and the focus is on how to obtain accurate time-varying frequency and amplitude of a nonlinear nonstationary signal. Here we propose the use of a conjugate-pair decomposition (CPD) method with the empirical mode decomposition (EMD) for characterization of membrane dynamics. First, EMD with signal conditioning techniques is used to separate a compound membrane response into well-behaved intrinsic mode functions (IMFs) without assuming the signal to be harmonic. Then, a pair of sliding conjugate functions is used to accurately extract the time-varying frequency and amplitude of each IMF by using only three neighboring data points for each time instant. Because the variations of frequencies and amplitudes of IMFs contain system characteristics, they can be used for system identification and damage detection. Experimental nonlinear responses of a horizontally tensioned Kapton membrane subjected to a transverse harmonic excitation provided by a shaker at one end are used to validate the proposed methodology. Results show that the clamped-clamped supports and pre-tension cause the first-mode vibration to have a hardening cubic nonlinearity, and several other nonlinear phenomena are identified.
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Xin Qian, Xin Qian, Xingwen Du, Xingwen Du, P. Frank Pai, P. Frank Pai, } "Dynamics characterization and health monitoring of membrane structures by time-frequency analysis", Proc. SPIE 7650, Health Monitoring of Structural and Biological Systems 2010, 765035 (9 April 2010); doi: 10.1117/12.847617; https://doi.org/10.1117/12.847617

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