A novel methodology based on the reflected L(0,1) guided wave for quantitative detection of corrosion-induced wall thickness loss in continuous pipes

Corrosion-induced wall thickness loss (CIWTL) can reduce the strength and integrity of a pipe, threatening its normal operation. Effective detection of CIWTL in pipes helps ensure their safe operation. This paper presents a novel methodology based on the reflected L(0,1) guided wave to quantitatively detect CIWTL in a continuous pipe. Investigating the effects of CIWTL and propagation length on time-of-flight (TOF) variation of the L(0,1) guided wave showed that increasing the accumulated propagation length of the L(0,1) mode improved its sensitivity to CIWTL. The reflected L(0,1) guided wave, which had a longer accumulated propagation length in a certain range, was generated by making discontinuities on both sides of a localized section within a continuous pipe. Then, the TOF variation of the reflected wave was proposed as a CIWTL-sensitive feature, and a quantitative relationship between the TOF variation of the reflected wave and CIWTL was theoretically established for quantifying the CIWTL of the pipe section. High-resolution measurement of CIWTL could be achieved through increased accumulated propagation length. Additionally, this methodology could be applied to measure CIWTL in the next pipe section and extended to realize the distributed detection of CIWTL in a continuous pipe. The effectiveness of this methodology was validated experimentally. The experimental results indicated that the L(0,1) mode was clearly reflected from artificial discontinuities, CIWTL in the pipe was sensitively identified and accurately quantified using the proposed method, and the values of the CIWTL measured by the proposed method were consistent with those measured by ultrasonic testing (UT). This methodology has higher estimation performance for CIWTL than current guided wave-based (GWB) methods.