Ultrasonic flaw detection using partial wavelet in offshore pipeline non-destructive evaluation

The noise suppression techniques with wavelet transform are widely used in non-destructive evaluation (NDE). In order to improve the SNR of the ultrasonic signals and detect the small defect buried in heavy noises, a method of identification of weak ultrasonic signals based on the partial wavelet transform is proposed in this paper. The support in frequency of the partial wavelet matches that of the ultrasonic signal very well. Applying the partial wavelet to the measured ultrasonic signal, the part of the signal related to the noise will be removed leaving only the correlated portion of the ultrasonic echoes. Numerical and experimental results show that this technique can be efficient in eliminating noise and detecting small flaw in non-destructive evaluation.