Affiliations: University of Liege, Aerospace and Mechanical
Engineering Department, Structural Dynamics Research Group, Chemin des
Chevreuils 1, B52, B-4000 Liege, Belgium
Abstract: An efficient approach to Structural Health Monitoring of dynamical
systems based on the Wavelet Transform (WT) and the concept of subspace angle
is presented. The objective is to propose a detection method that is sensitive
to the onset of nonlinear behaviour in a dynamic system. For this purpose,
instantaneous frequencies are identified first from output-only vibration
signals using the Wavelet Transform. Time varying deformation shapes are then
extracted by analyzing the whole measurement data set on the structure. From
this information, different dynamic states of the structure may be detected by
inspecting time variations of 'modal' features. The experimental structure
considered here as application example is a clamped beam with a geometric
nonlinearity. Detection of nonlinearity is carried out by means of the concept
of subspace angles between instantaneous deformation modes extracted from
measurement data using the continuous Wavelet Transform. The method consists
in controlling the angular coherence between active subspaces of the current
and reference states respectively. The proposed technique, which shows a good
sensitivity to small changes in the dynamic behaviour of the structure, may
also be used for damage detection.
