Investigation of the effect of a bend on pipe inspection using microwave NDT
Investigation of the effect of a bend on pipe inspection using microwave NDT
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DOI：
10.1016/j.ndteint.2019.102208
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发表时间：
2020-03-01
影响因子：
4.2
通讯作者：
Hashizume, Hidetoshi
中科院分区：
文献类型：
--
作者：
Chen, Guanren;Katagiri, Takuya;Hashizume, Hidetoshi
本研究调查了弯曲对用于快速管道检测的微波 NDT（无损检测）的影响。从理论上推导了弯曲引起的微波模式转换的影响因素，并通过数值模拟进行了验证。理论和数值结果都表明，弯曲处的模式转换实际上是由任意模式的截止频率归一化的频率（f/f(c)）、曲率半径与管道内径之比（r/D）和弯曲角度（α）决定的。随后的实验评估使用了四组不同内径和五个不同弯度的管道。通过比较直管和弯管中管壁减薄的反射信号来定量评估弯曲的影响。结果表明，弯曲的存在导致弯曲后面的反射信号下降，下降的程度还取决于弯曲的r/D和α。此外，当弯曲尺寸一定时，管壁减薄的长度或深度不会明显影响反射信号的减少。
This study investigated the effect of a bend on microwave NDT (non-destructive testing) applied for rapid pipe inspections. The factors affecting the mode conversion of microwaves due to a bend were deducted theoretically and verified through numerical simulation. Both theoretical and numerical results revealed that the mode conversion at a bend was actually determined by the frequency normalized by the cut-off frequency of an arbitrary mode (f/f(c)), the ratio of the curvature radius to the inner diameter of the pipe (r/D) and the bend angle (alpha). Subsequent experimental evaluations were performed using four groups of pipes with different inner diameters and five different bends. The effect of a bend was quantitatively evaluated by comparing the reflection signals from pipe wall thinning in a straight pipe with those in a bent pipe. The results showed that the presence of a bend led to a decrease in the reflection signal behind the bend, and the extent of decrease also depended on r/D and alpha of the bend. Furthermore, the length or the depth of the pipe wall thinning did not noticeably affect the decrease in reflection signal, when the bend's dimensions were certain.