Leinov Eli, Lowe Michael J S, Cawley Peter
Non-Destructive Evaluation Group, Department of Mechanical Engineering, Imperial College, London SW7 2AZ, United Kingdom.
J Acoust Soc Am. 2016 Dec;140(6):4528. doi: 10.1121/1.4972118.
The application of long-range guided-wave testing to pipes embedded in concrete results in unpredictable test-ranges. The influence of the circumferential extent of the embedding-concrete around a steel pipe on the guided wave propagation is investigated. An analytical model is used to study the axisymmetric fully embedded pipe case, while explicit finite-element and semi-analytical finite-element simulations are utilised to investigate a partially embedded pipe. Model predictions and simulations are compared with full-scale guided-wave tests. The transmission-loss of the T(0,1)-mode in an 8 in. steel pipe fully embedded over an axial length of 0.4 m is found to be in the range of 32-36 dB while it reduces by a factor of 5 when only 50% of the circumference is embedded. The transmission-loss in a fully embedded pipe is mainly due to attenuation in the embedded section while in a partially embedded pipe it depend strongly on the extent of mode-conversion at entry to the embedded-section; low loss modes with energy concentrated in the region of the circumference not-covered with concrete have been identified. The results show that in a fully embedded pipe, inspection beyond a short distance will not be possible, whereas when the concrete is debonded over a fraction of the pipe circumference, inspection of substantially longer lengths may be possible.
将远程导波检测应用于埋入混凝土中的管道会导致不可预测的检测范围。研究了钢管周围嵌入混凝土的周向范围对导波传播的影响。使用解析模型研究轴对称完全埋入管道的情况，同时利用显式有限元和半解析有限元模拟来研究部分埋入管道。将模型预测和模拟结果与全尺寸导波测试进行比较。发现一根8英寸钢管在轴向长度0.4米范围内完全埋入时，T(0,1)模式的传输损耗在32至36分贝之间，而当仅50%的圆周被埋入时，传输损耗降低了5倍。完全埋入管道中的传输损耗主要是由于埋入部分的衰减，而在部分埋入管道中，它强烈依赖于进入埋入部分时的模式转换程度；已识别出能量集中在未被混凝土覆盖的圆周区域的低损耗模式。结果表明，在完全埋入的管道中，短距离之外的检测将无法进行，而当混凝土在管道圆周的一部分上脱粘时，可能进行更长长度的检测。
