The present article provides a state‐of‐the‐art review of imaging techniques used for defect detection of fiber reinforced polymer (FRP)‐bonded civil engineering structures. Compared to the conventional techniques by equipping a structure with stress wave sensors, the contactless imaging techniques feature efficient instrumentation, convenient data acquisition, and rapid evaluation in the procedures of nondestructive testing (NDT). Recently, a substantial progress in utilizing electromagnetic waves for development of imaging NDT techniques (e.g., synthetic aperture radar, infrared thermography, laser shearography, and laser reflection technique) with the purpose to identify debonding or delamination of FRP‐bonded structural systems has been made. As another electromagnetic wave‐based imaging technique, X‐ray computed tomography is promising for exploration of the damage evolution in this structural system, despite little application in structural health monitoring of real infrastructures. Apart from these imaging techniques, more recently, there have been computer‐aided motion magnification techniques for defect identification. The motion magnification technique only requires a digital camera and a computer with vision algorithm, which can amplify the motion of defect region and render it visible in a video. This advanced imaging technique achieves high‐resolution measurement, simultaneous full‐field inspection, and straightforward defect identification in the scene. In this review, both Eulerian motion magnification and phase‐based motion magnification techniques for structural visual inspection are presented and discussed. Furthermore, the present article recommends the combination of imaging NDT techniques with artificial intelligence approaches (e.g., deep learning algorithms) to realize the automated and efficient defect detection towards FRP‐bonded civil infrastructures.

中文翻译：

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纤维增强聚合物粘合民用基础设施缺陷检测的成像技术

本文对用于纤维增强聚合物（FRP）粘结的土木工程结构缺陷检测的成像技术进行了最新的综述。与通过为结构配备应力波传感器的传统技术相比，非接触式成像技术具有高效的仪器，便捷的数据采集以及在无损检测（NDT）过程中进行快速评估的功能。最近，在利用电磁波发展成像无损检测技术（例如合成孔径雷达，红外热成像，激光剪切成像和激光反射技术）方面取得了实质性进展，目的是识别FRP粘合结构系统的剥离或分层。 。作为另一种基于电磁波的成像技术，尽管很少在实际基础设施的结构健康监测中使用X射线计算机断层摄影术，但有望探索该结构系统中的损伤演化。除了这些成像技术外，最近还出现了计算机辅助运动放大技术，用于缺陷识别。运动放大技术仅需要数码相机和具有视觉算法的计算机，它们可以放大缺陷区域的运动并使其在视频中可见。这项先进的成像技术可实现高分辨率测量，同步全视场检查以及现场的直接缺陷识别。在这篇综述中，提出并讨论了用于结构视觉检查的欧拉运动放大率和基于相位的运动放大率技术。此外，