Cable terminals of the high-speed electric multiple units (EMUs) are prone to undertake insulation delamination defects due to their special operating conditions. Such a defect is difficult to identify and it may pose a great threat to the safety of the EMUs. To achieve accurate detection of insulation delamination defects, this article proposes a terahertz (THz)-based approach that combines the spectrum of the THz wave and THz imaging techniques. Specifically, a synthetic multilayer composite insulation structure with an air gap is firstly built to simulate the internal delamination defect of the cable terminal. Then THz tests in both time and frequency domains are performed on the synthetic structure. Experimental results show that the delamination defect of the multilayer insulation structure can be quickly detected by observing the absorption spectrum in the THz frequency domain. The location and geometry of the defect can be preliminarily determined by the THz imaging and then further refined through image segmentation. In addition, the thickness of the delamination defect can be quickly calculated by the THz time-domain spectrum (TDS). By combining the THz spectrum and the THz imaging information, the delamination defects are quantitatively detected for the multilayer composite structure or even for the EMU’s cable terminals.

中文翻译：

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基于太赫兹的车辆电缆终端绝缘分层缺陷检测

高速动车组电缆终端由于其特殊的运行条件，容易产生绝缘分层缺陷。这种缺陷很难识别，可能对动车组的安全造成很大威胁。为了实现绝缘层分层缺陷的准确检测，本文提出了一种基于太赫兹 (THz) 的方法，该方法结合了太赫兹波的频谱和太赫兹成像技术。具体而言，首先构建了具有气隙的合成多层复合绝缘结构，以模拟电缆终端的内部分层缺陷。然后对合成结构进行时域和频域的太赫兹测试。实验结果表明，通过观察太赫兹频域的吸收光谱，可以快速检测出多层绝缘结构的分层缺陷。缺陷的位置和几何形状可以通过太赫兹成像初步确定，然后通过图像分割进一步细化。此外，还可以通过太赫兹时域谱（TDS）快速计算出分层缺陷的厚度。通过结合太赫兹光谱和太赫兹成像信息，定量检测多层复合结构甚至动车组电缆终端的分层缺陷。通过太赫兹时域频谱（TDS）可以快速计算出分层缺陷的厚度。通过结合太赫兹光谱和太赫兹成像信息，定量检测多层复合结构甚至动车组电缆终端的分层缺陷。通过太赫兹时域频谱（TDS）可以快速计算出分层缺陷的厚度。通过结合太赫兹光谱和太赫兹成像信息，定量检测多层复合结构甚至动车组电缆终端的分层缺陷。