Crack detection in simply supported beams using stationary wavelet transform of modal data

Abstract

A new approach, based on Stationary Wavelet Transform (SWT), is proposed in this paper for crack detection in beam-like structures. SWT is different from Discrete Wavelet Transform (DWT); SWT is a redundant transform that doubles the number of input samples at each iteration, which can provide a more accurate estimation of the variances and facilitate the identification of salient features in a signal, especially for recognizing noise or signal rupture.The mode shape of a cracked beam with a small crack depth, while apparently a single smooth curve, actually exhibits a local peak or discontinuity in the region of damage. The mode shape 'signal' can be approximately considered as that of the intact beam contaminated by 'noise' which consists of response noise and the additional response due to the crack. In this way, the signal can be decomposed by SWT into a smooth curve, called approximation coefficient, and a detail coefficient curve, which includes crack information that is useful for damage detection, respectively. In this paper, the modal responses of damaged simply supported beams are computed using the finite element method. The effect of noise on the proposed method is also studied. The numerical and experimental results demonstrate the efficiency of the proposed method for crack detection. It is shown that SWT of the modal data of cracked simply-supported beams provides a better crack indication than conventional DWT. The relationship between SWT detail coefficient and crack size (depth and width) are also discussed. A new method based 2 on the average difference of the SWT detail coefficient of vibration bending modes of a cracked beam and an intact beam is proposed as a damage index and verified.

Time-domain analysis of piezoelectric impedance-based structural health monitoring using multilevel wavelet decomposition

“…In this case, a lead zirconate titanate (PZT) transducer was used as a vibration sensor. There are many other efforts proposing wavelet based methods for SHM in civil structures [3][4][5]. Some of them are used to identify modal parameters and others are based on Lamb waves, as found in [6,7] and in [8], respectively.…”

Detection of cracks in simply-supported beams by continuous wavelet transform of reconstructed modal data

“…It should be noted that this simple algorithm is similar to but different from the hard-thresholding function used in previous work [27][28][29]. Fig.…”

Seismic damage detection of tall airport traffic control towers using wavelet analysis

“…In DWT, detail coefficients contain the information necessary to detect cracks in structures (Ovanesova & Suarez, 2004;Zhong & Oyadiji, 2011). Further details on wavelet theory can be found in the literature (e.g.…”

“…Wilde (2006, 2010) for damage detection of beams and plates proposed using wavelets which create maximum number of wavelet coefficients that are close to zero. Zhong and Oyadiji (2011) mentioned that for optimal selection of basis functions, a tradeoff between number of vanishing moments and effective support of a wavelet should be carried out. Hester and Gonzalez (2012) employed Mexican Hat wavelet to propose a damage detection algorithm based on bridge acceleration response to a vehicle.…”

“…In addition, they concluded that CWT is more suitable for damage detection than DWT due to precise resolution which is necessary for damage localisation. Zhong and Oyadiji (2011) employed Stationary Wavelet Transform (SWT) of modal data for crack detection in simply supported beams. They used modal displacement data to identify and locate damage.…”