This study evaluated the effect of pipe diameter on the applicability of a technique using TE11 mode microwaves for in-pipe crack detection. Three TE11 mode converters of different inner diameters were designed based on theoretical calculations and verified via numerical simulations. The working bandwidths of these mode converters were 7.0, 4.0, and 1.9 GHz. Experimental verification was carried out using brass pipes with the corresponding three inner diameters, and with pipe lengths up to 21–25.5 m. An axial and a circumferential slit were introduced to simulate cracks and deployed at multiple positions along the pipes under test. The results showed that both axial and circumferential slits could be detected and located for an inner pipe diameter up to 39 mm and at a distance of 15 m–24 m.

中文翻译：

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使用TE 11模式微波对多个直径进行管内裂纹检测

这项研究评估了管径对使用TE11模式微波进行管内裂纹检测的技术的适用性的影响。根据理论计算设计了三种不同内径的TE11模式转换器，并通过数值模拟对其进行了验证。这些模式转换器的工作带宽为7.0、4.0和1.9 GHz。使用具有相应三个内径且管长最大为21–25.5 m的黄铜管进行了实验验证。引入轴向缝隙和圆周缝隙以模拟裂纹，并沿被测管道在多个位置展开。结果表明，对于内径最大为39 mm且距离为15 m–24 m的管道，都可以检测到轴向和圆周方向的缝隙。