Experimental structural damage localization in beam structure using spatial continuous wavelet transform and mode shape curvature methods

An experimental dynamic vibration test using a non-contact scanning laser vibrometer is performed in order to extract the deflection shapes of two aluminium beams containing a notch cut out with a mill and two carbon/epoxy composite beams containing an impact damage of different severities. All of the beams are subjected to the clamped-clamped boundary conditions. These shapes are used as an input in a continuous wavelet transform technique for damage detection. In total, 78 wavelet functions with scale factors from 1 till 128 are used for the aluminium beams, whereas deflection shapes for composite beams are obtained in two dimensions, thus a two-dimensional wavelet transform is employed using 16 wavelet functions, all at scales from1 till 16. The scale, which is most suitable for damage identification, is found by calculating standardized damage index and the parameter called damage estimate reliability for the scales under investigation. Another method, based on mode shape curvature squares, is also applied to identify the damage. A baseline data of deflection shapes at a healthy state is not required for both methods to work. Damage identification results are compared for both methods. To assess the robustness of an algorithm involving both methods, different sensor densities are simulated by reducing the input deflection shapes by integer factors.