Experimental investigation of stochastic vibration of nonlinear structures

The purpose of this experimental investigation is to measure the dynamic response of an aeroelastic structure involving nonlinear coupling to random parametric vibration. Two main series of tests are conducted under two different bandwidths. The first test corresponds to isolation of the first normal mode natural frequency. The second test corresponds to a bandwidth which covers the second normal mode frequency. The tests are conducted when the structure is tuned internally such that the second normal mode frequency is twice the first normal mode frequency. Experimental measurements are processed to estimate the response mean squares. The influence of excitation spectral density level and internal detuning on the response mean squares is examined. The results confirm regions of instability as predicted in harmonic excitation but there is no evidence of the well known saturation phenomenon. The results differ from the theoretical results obtained for the same model under white band random excitation. This disagreement is mainly due to the fact that the excitation is represented by a physical white noise process in the analytical model while it is a band— limited process in the actual experiment.