Guided Wave Electromagnetic Ultrasonic Scattering Imaging

At present, there are few studies on the defect imaging using guided wave scattering method. Most of the defect detection based on guided wave scattering is limited to the location of the defects, and the defects studied are mostly artificial defects of standard contour shape. The researches on defect imaging utilized transmitted guided waves. However, (1) the analysis and processing of the guided wave detection signal are greatly affected by the scattering effect of the guided wave after encountering the defect, resulting in a large error in the characteristics of the guided wave, amplitude, and other guided wave signals extracted from the guided wave detection signal. This has a negative impact on the accuracy of defect imaging; (2) the defect size accounts for a small proportion of the transmitted ray, and the propagation delay caused by the variation of the wave speed caused by the thickness reduction in the defect is small. In particular, when the distance between the two transducers is relatively long or the guided wave propagation path is long, the propagation delay caused by the thickness reduction in the defect is smaller, which has a serious negative impact on the imaging accuracy of the defect; (3) for the defects with shallow depth and clear outline, the variation of the thickness of the material is not obvious, and the transmission guided wave imaging method based on the thickness map has lower accuracy for the contour of this type of defect.