Differential Electromagnetic Acoustic Probes for Quantitative Detection of Pipeline Cracks

Abstract

The circumferential 0-mode shear horizontal (CSH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) guided waves have great advantages for the detection of cracks in pipelines due to the small attenuation of acoustic signals. However, the CSH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> guided wave detection methods are confused by the signal mixing, low signal-to-noise ratio and poor quantitative accuracy of cracks. In this paper, the novel detection method which includes three circumferential uniformly distributed probes are proposed for quantitative detection of pipeline cracks. The signals received by two receiving probes constitute a couple of differential signals. A full physical field coupled finite element model is developed to study the effect of CSH guided wave-defect interactions. The differential signal enhancement algorithm can separate the crack signal from the overlapped signal, which greatly improves the accuracy of crack location. The characteristic coefficient method is introduced to improve the quantitative accuracy of the crack sizes. The localization and quantification methods are verified through experiments. The results show that the defect localization method proposed in this paper can improve the signal-to-noise ratio of the crack signal from -15 dB to 2.4 dB. The localization error of crack is less than 6.75%. The quantitative error of the crack sizes is less than 8.75% based on the characteristic coefficient method.