Scale-wavenumber domain filtering method for curvature modal damage detection

In damage assessment of composite structures, the modal curvature appears to be one of the most important damage indices in the past decades. However, a noticeable deficiency of the modal curvature is its susceptibility to noise, which is mainly induced by the numerical difference estimation. This study proposes the scale-wavenumber domain filtering method based on the combination of the continuous wavelets transform, the discrete Fourier transform-based modal curvature and the scale wavenumber domain filtering method. The continuous wavelet transform provides the scale domain for noisy mode shape analysis, in which the normal fluctuations and the noise-induced fluctuations are filtered from the inspected mode shapes. The discrete Fourier transform-based modal curvature supplies the wavenumber domain expressions of the scaled mode shapes. In the scale and wavenumber domains, some special filters are designed and used in noise suppression. The effectiveness of the proposed method is analytically verified by employing the cracked composite beam model, and the performance is further validated by the experimental data from the carbon-fiber-reinforced polymer beam with crack. Based on these validations, it is observed that the proposed method is capable of revealing slight damage in noisy condition, without the requirement for the prior knowledge of material properties.