Owing to their inherent advantages, non-metallic structures such as glass reinforced epoxy (GRE) pipes and high-density polyethylene (HDPE) pipes are rapidly replacing their steel counterparts in pipeline infrastructures. However, non-metallic pipes are vulnerable to a variety of defects which compromise their structural integrity. Hence, periodic inspection of these structures is incumbent to ensure their structural integrity and avoid catastrophic in-service failures. Microwave and millimeter wave non-destructive evaluation techniques have shown great potential for inspecting non-metallic structures due to their high sensitivity, resolution, and cost-effectiveness. However, most of the previous investigations performed on microwave non-destructive testing (NDT) of these particular structures are deemed limited since these investigations considered one probe type and often conducted over narrow frequency band. Furthermore, many of the previous microwave NDT investigations considered unrealistically large defects which renders the reported conclusions about the performance envelope of microwave NDT of non-metallic pipes rather inaccurate. Consequently, an uncertainty still exists in the domain with regards to detection capability of the method when the defects in the pipes are actually small in size. Unlike all previous investigations, a comprehensive and realistic microwave imaging of GRE and HDPE pipes with embedded defects of practical importance is demonstrated in this paper. In order to image these defects, various near-field probes operating at wide range of frequencies are employed and compared herein. The relative performance and the effectiveness of microwave NDT for non-metallic pipe inspection using these probes are quantitatively reported. Furthermore, the images of the HDPE pipe produced by microwave probes are benchmarked to phased array ultrasonic testing.

中文翻译：

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玻璃钢环氧和高密度聚乙烯管的微波无损评价

由于其固有的优势，玻璃增强环氧树脂（GRE）管和高密度聚乙烯（HDPE）管等非金属结构正在迅速取代管道基础设施中的钢结构。然而，非金属管道容易受到损害其结构完整性的各种缺陷的影响。因此，必须定期检查这些结构，以确保其结构完整性并避免灾难性的服役故障。微波和毫米波无损评估技术由于其高灵敏度、分辨率和成本效益，在检测非金属结构方面显示出巨大的潜力。然而，之前对这些特定结构的微波无损检测 (NDT) 进行的大多数调查都被认为是有限的，因为这些调查考虑了一种探头类型并且通常在窄频带上进行。此外，以前的许多微波无损检测研究都考虑了不切实际的大缺陷，这使得报告的关于非金属管道微波无损检测性能包线的结论相当不准确。因此，当管道中的缺陷尺寸实际上很小时，该方法的检测能力仍然存在不确定性。与之前的所有研究不同，本文展示了具有实用重要性的嵌入缺陷的 GRE 和 HDPE 管道的全面而逼真的微波成像。为了对这些缺陷进行成像，本文采用并比较了在宽频率范围内工作的各种近场探头。定量报告了使用这些探头进行非金属管道检测的微波无损检测的相对性能和有效性。此外，微波探头产生的 HDPE 管的图像以相控阵超声检测为基准。