Rail Crack Monitoring Using Acoustic Emission Technique by Dan Li

Author:Dan Li
Language: eng
Format: epub, pdf
Publisher: Springer Singapore, Singapore

(3.14)

Equation (3.14) is regarded as a zero-phase digital filter that preserves the initial amplitude, frequency and phase relations of extracted components. The cutoff frequency could even be a function of time. More significantly, based only on the forward Hilbert transform, it is easier to be implemented than the filtering techniques based on wavelet packet and wavelet transform, and hence provides a new noise cancellation approach for AE signals of high non-stationarity. Figure 3.16 reveals the concept of HT-based noise cancellation method for rail crack detection, where the block diagram of digital filter is included. The energy of rail operational noise, considered as , is predominantly focused in relatively lower frequency range than that of crack-induced AE signal, considered as . A two-stage filtering process is designed in order to eliminate the aliasing and phase reversal due to discretization of signal. Through an appropriate cutoff frequency , the SNR of AE signals inundated with noise will be greatly improved.

Fig. 3.16HT-based noise cancellation method: a flowchart of concept and b block diagram of HT-based digital filter

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