Modal Damping Identification for a Structurally Nonlinear Airfoil using Sweep Excitation

摘要

It seems probable that the presence of nonlinear harmonics in the system response, when analysed using the spectral analysis method, results in a distortion of the transfer function. The first mode resonant peak is wider than for the equivalent linear system and provides an overestimate of the modal damping. The fact that the transfer function calculated directly from the peaks in the time series response yields damping values similar to the linear values suggests that the increased damping values obtained using the spectral analysis is in error. The error is caused by the nonlinear waveforms producing harmonic responses at frequencies near the first mode natural frequency, thus increasing the bandwidth of the transfer function in this area.