Abstract

Laser generated Lamb wave (LW) is a promising NDT tool for structural health monitoring because it is a non-contact inspection technique and capable of providing long-distance inspection manner. However, an experienced operator must be hired to analyze the reflected LW signals so that the location of each detected defect can be known. This paper reports a research method that can automatically determine the location of defect using laser generated LW. After the emission of LW to the inspected plate, a de-noising technique called continuous wavelet transform and canny edge detection were employed to automatically locate defect like images from the LW signals reflected from the plate. The whole spectrum of wavelet coefficients was processed as an image and the canny edge detector was applied to minimize interference and enhance the target for the first time. Then an ellipse algorithm was used to locate each defect occurred in the plate by only using three enhanced LW signals rather than scanning the entire surface of the plate done by conventional methods. To verify the effectiveness of the proposed method, experiments were conducted with promising results. Significant processing time and intensive human visual inspection can be reduced. Moreover, the method can be applied to production line for automatic plate integrity inspection.

How to Cite:

Tse, P. W., Wang, G. . & Chen, J. ., (2019) “Laser generated Lamb wave and Canny edge technique for automatically locating defects occurred in plates”, Review of Progress in Quantitative Nondestructive Evaluation .