Application of complex wavelet transform in ultrasonic detection practice

The presence of numerous disturbing signals, which may be created when ultrasonic energy meets micro defects (e.g. microcracks, voids or inclusions contained in material) during its propagation, makes it hard to distinguish the true feedback signal that indicates the object being inspected. Additionally, due to the anisotropic feature of the propagation of ultrasonic energy, the position of the true feedback signal often fluctuates more or less. In order to tackle this difficult problem, the complex wavelet transform was adopted and two feasible methods-the complex wavelet based envelope detection method and the complex wavelet based correlation analytical method-were developed for analyzing the ultrasonic signals collected by using the shear wave ultrasonic transducer. Experiments prove that, by using the proposed methods, the true feedback signal that indicates the object being inspected may be distinguished successfully and thereby its position is determined correctly. This is undoubtedly helpful for further improving the accuracy of ultrasonic detection significantly.