The Algorithm for Defect Characterization in Guided Wave Based Pipeline Inspection

Pipelines are crucial infrastructure that every modern city need. Pernicious external impacts or hazardous operating environment applied on pipeline can easily cause the occurrence of defects in the pipeline. Such situation has a serious impact on the reliability of in-service pipeline. Thus the ability to accurately inspect defect and estimate its profile such as size and severity is important for practical NDE techniques. Guided waves have been successfully employed as an innovative technique for sufficiently and rapidly screening pipeline for defect inspection. In this paper, we firstly present the results of a series of experiments conducted on the pipeline in which a simulated circumferential defect was introduced. It was found that the reflection from a defect involves the superposition and interference of signals at the front-end and back-end of defect. The axial extent of defect can be identified through separating out the signals reflected from two ends and extracting time shifting information. The experiment based method and frequency analysis based method have been accordingly developed in this paper. The outcome of this study can be treated as a foundation for the qualitative characterization of dimensional parameters of defect in pipeline.