Continuous wavelet transforms and curvatures of vibration shapes have been widely used for vibration-based structural damage detection in the past few decades. Continuous wavelet transforms and curvatures of vibration shapes have proved capable of localizing and manifesting effects of damage on vibration shapes in forms of local anomalies. The damage can be identified in neighborhoods of the anomalies that exist in the continuous wavelet transforms and curvatures of the vibration shapes, and the anomalies can be further manifested by comparing the continuous wavelet transforms and curvatures of vibration shapes with those of an associated undamaged structure, which can be considered baseline information. Meanwhile, Lamb waves have been widely used for structural damage detection and proved effective for identifying small-sized structural damage in a relatively large-sized structure due to their damage-sensitivity and long range of propagation. In this paper, a baseline-free structural damage detection method is developed using continuous wavelet transforms of Lamb wave propagation. The term “baseline-free” indicates that the proposed method can be used to identify structural damage without referring to any a priori information of an undamaged structure associated a test structure, such as its complete geometry, material properties, boundary conditions, modal parameters, and vibration shapes; the proposed method assumes that a test structure is geometrically smooth and made of materials that have no stiffness discontinuities. In this method, a three-dimensional curvature damage indices are defined for beam-like structures based on multi-scale continuous wavelet transforms of Lamb wave propagation. The three dimensions correspond to the time- and space-domains of the propagation and the scale of a continuous wavelet transform. It can be proved that the continuous wavelet transform of Lamb wave propagation with the Gaussian wavelet function of the n-th order has a shape resembles that of the n-th-order derivative of Lamb wave propagation. Two major advantages of the proposed method are: (1) curvatures of Lamb wave propagation are calculated as second-order Gaussian wavelet transforms of the Lamb wave propagation with high signal to noise ratios, compared with those calculated by a finite difference scheme; and (2) the proposed method is applicable to Lamb wave propagation at a wide range of frequencies. A numerical investigation of the proposed method is conducted on a damaged beam-like structure, which is excited by a ﬁve-peak tone-burst waves with different center frequencies. Lamb wave propagation of the structure is measured with different levels of random noise added to simulate measurement noise. An experimental investigation was conducted verify results from the numerical investigation.


Baseline-Free Structural Damage Identification Using Continuous Wavelet Transforms of Lamb Wave Propagation

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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