Crack detection on beams by Hilbert-Huang transform of transient flexural waves
Date Issued
2010
Date
2010
Author(s)
Lin, Cheng-Wei
Abstract
In the industry, the damage detection of structures is an important research subject. To this end, a proper method for the vibration signal processing is indispensable. The Hilbert-Huang Transform (HHT), which has been successfully applied to many different fields in the last ten years, may provide a promising method for this purpose. The purpose of this research is to detect the crack on beams by HHT of transient flexural waves. First of all, the basic method named “Empirical Mode Decomposition” of HHT was introduced. Its basis of expansion is adaptive, so that it can produce physically meaningful representations of data from nonlinear and non-stationary processes. And then the difference of Bernoulli-Euler theory and Timoshenko theory associated with flexural waves were then discussed. It will be found that the flexural waves are dispersive by considering the wave velocity. Besides, the beams of Aluminum, Brass and Stainless Steel were considered in the experiments. The flexural waves were made by the impact force on beams. Applying the HHT on the measured acceleration data, the Hilbert spectrum can be obtained. From the figure the ridges represented the reflected waves from the boundary and the crack. By estimating the wave arrival time, the wave velocity and the crack location can be determined. The mean values of absolute relative error are all less than 2.5%. In addition, the characteristics on Hilbert spectrum of the damage size were also studied. This study may contribute to the damage size estimation in the near future.
Subjects
crack detection
Hilbert-Huang Transform
Empirical Mode Decomposition
flexural wave
dispersive wave
Timoshenko beam
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