毫米波检测热障涂层缺陷的方法研究

在毫米波段利用CST微波工作室仿真软件对热障涂层脱黏和热生长氧化层(Thermal growth oxide，TGO)的无损检测进行理论仿真研究，目的是确定不同工作频率段检测时的检测灵敏度和分辨率，以指导试验检测中波导探头的选择。在40～50 GHz和50～60 GHz两个频率段对热障涂层中陶瓷顶层和黏结层间的脱黏检测进行研究，主要包括由裂缝演变为脱黏时脱黏宽度的检测，脱黏面积及形状的检测和脱黏层厚度的检测。在18～26.5 GHz，26.5～40 GHz，40～50 GHz和50～60 GHz4个频率段对热障涂层中TGO层的厚度进行检测。结果显示，在毫米波段可以利用反射系数的相位差来良好的表征长脱黏的宽度，面脱黏时的脱黏面积，大脱黏时的脱黏深度以及TGO层的厚度;采用的工作频率越高时检测的灵敏度越高，并且对检测参数的检测分辨率越高。

Feasibility Study on Defects Detection of Thermal Barrier Coatings Using Millimeter Wave

The objective of this study is to investigate feasibility of millimeter wave nondestructive testing to detect the defects of TBCs and to determine sensitivity of detection when frequency changed. The simulation to monitor the delamination of TBCs and TGO are carried out using computer simulation technology-microwave studio. WR18 rectangular waveguide (40-50 GHz) and WR14 rectangular waveguide (50-60 GHz) are used to detect the delamination of TBCs. The depth of cracks (parallel to the interface of TC and BC), the size of the shape of delimation, the thickness of delimation are studied. Four rectangular waveguides, including WR42 (18-26.5 GHz), WR28 (26.5-40 GHz), WR18 (40-50 GHz) and WR14 (50-60 GHz), are used to detect TGO. The changes in the phase of reflection coefficient are primarily studied. The results show that the phase difference of reflection coefficients can represent not only the existence of the defect, but also the depth of the defect. When the delamination surface is less than the aperture of the waveguide probe, the phase of reflection coefficient can represent the size of delamination. When the delamination surface is more than the aperture of the waveguide probe, the phase of reflection coefficient can represent the thickness of delamination. The phase difference of reflection coefficient can represent the TGO thickness. Besides, the sensitivity is greater in high frequency than low frequency.