Experimental investigation of reflection in guided wave-based inspection for the characterization of pipeline defects

In guided wave-based pipeline inspection, the reflection from a defect usually includes sufficient defect-relevant information. It has been found that the reflection of guided waves at defect is the joint result of interference between reflections from both its front and back edges. However, the majority of published work has only studied and considered the overall resulting reflection signal for the inspection-related tasks. This paper reports the findings of extensive experimental investigation on the effects of a defect's geometric parameters on the two reflection signals from the respective edge of defect. We show that the two edge reflections present different signal features, which further results in the complexity of the overall reflection signal from the defect. We accordingly propose a new strategy that considers the extraction of two edge reflection signals embedded in overall reflection signal and the use of the identified edge signals so as to enable an accurate and quantitative pipeline defect characterization. (C) 2010 Elsevier Ltd. All rights reserved.