IEEE Trans Ultrason Ferroelectr Freq Control. 2017 May;64(5):847-858. doi: 10.1109/TUFFC.2017.2683259. Epub 2017 Mar 15.
Detection and monitoring of corrosion and erosion damage in pipe bends are open challenges due to the curvature of the elbow, the complex morphology of these defects, and their unpredictable location. Combining model-based inversion with guided ultrasonic waves propagating along the elbow and inside its walls offers the possibility of mapping wall-thickness losses over the entire bend and from a few permanently installed transducers under the realm of guided wave tomography (GWT). This paper provides the experimental demonstration of GWT of pipe bends based on a novel curved ray tomography algorithm and an optimal transducer configuration consisting of two ring arrays mounted at the ends of the elbow and a line of transducers fixed to the outer side of the elbow (extrados). Using realistic, localized corrosion defects, it is shown that detection of both the presence and progression of damage can be achieved with 100% sensitivity regardless of damage position around the bend. Importantly, this is possible for defects as shallow as 0.50% of wall thickness (WT) and for maximum depth increments of just 0.25% WT. However, due to the highly irregular profile of corrosion defects, GWT generally underestimates maximum depth relative to the values obtained from 3-D laser scans of the same defects, leading in many cases to errors between 3% WT and 8% WT.
由于弯管的曲率、这些缺陷的复杂形态以及它们不可预测的位置，检测和监测弯管的腐蚀和侵蚀损伤是一个开放性挑战。将基于模型的反演与沿弯管传播的导波相结合，并利用其壁内的导波，为整个弯管的壁厚损失映射提供了可能，并且从几个永久安装在导波层析成像（GWT）领域的换能器中进行映射。本文基于一种新的弯曲射线层析成像算法和一种由两个安装在弯管两端的环形阵列以及一个固定在弯管外侧（外凸面）的线性换能器组成的最优换能器配置，提供了弯管 GWT 的实验演示。利用现实的局部腐蚀缺陷，结果表明，无论损伤在弯管周围的位置如何，都可以实现 100%的灵敏度来检测损伤的存在和进展。重要的是，对于壁厚仅减少 0.50%的缺陷，以及壁厚最大增加 0.25%的缺陷，这都是可行的。然而，由于腐蚀缺陷的高度不规则轮廓，相对于对同一缺陷进行的 3-D 激光扫描获得的值，GWT 通常会低估最大深度，在许多情况下，误差在 3%WT 和 8%WT 之间。
