Application of Hilbert Transform for Flaw Characterization in Ultrasonic Signals

Ultrasonic Testing is the highly reliable Non Destructive Testing (NDT) technique for flaw detection in steel weldments. Ultrasonic test signals are analyzes to identify the nature of the defect. In this paper, Hilbert transform is used for decomposing the ultrasonic test signals into high and low frequency components (namely Intrinsic Mode Function). These components are characterised in terms of Power Spectral Density (PSD). An attempt has been successfully made to classify the flaws based on PSD. It is found that power spectral density of planar defects is higher than volumetric defects for the fourth Intrinsic Mode Function.