PZT transducer array enabled pipeline defect locating based on time-reversal method and matching pursuit de-noising

Abstract

In the process of pipeline structural health monitoring, it is necessary to detect pipe defects as well as to locate the defect’s axial and circumferential positions. Axial locating of a pipeline defect can be achieved by identifying the defect reflection packets in the direct detected axial displacement time history signals. In practice, various kinds of noise are involved in the actual detection signal. Using the matching pursuit (MP) algorithm based on a custom over-complete waveform dictionary, the noisy detection signal can be effectively de-noised, and the defect’s axial position can be located. The time-reversal method used in a waveguide leads to temporal and spatial focusing, and this feature is used to locate the defect’s circumferential position in the pipeline. In this paper, a new pipeline defect locating approach based on the time-reversal method and MP de-noising is proposed. The integration of the finite element method (FEM) numerical simulation with experiment is utilized to locate the pipeline defect. The defect axial position Lx is located by the direct detected signal obtained from the actual pipeline defect detection experiment, after MP de-noising. A defect-free FEM reference model is established, and it has the same geometric and material parameters as the actual pipeline. Re-generating the time reversed defect reflection and the converted mode signals in the reference model, the energy will focus on the Lx position. After obtaining the maximum values of the axial displacement time history signals received from the reference model at the Lx position, the polar coordinate map based on these maxima can be plotted. The defect circumferential position is located based on the maximum values on the map. The FEM numerical simulation and experimental results are performed in this research. The defect locating results agree well with the actual pipeline defects, in both the axial and the circumferential directions.