摘要:
基于微波在介电材料中的传播理论及其对金属界面特性的敏感性, 利用CST-微波工作室(computer simulation technology-microwave studio)对微波检测热障涂层下金属的裂缝进行了仿真计算, 研究了热障涂层的厚度、 裂缝方向对检测结果的影响, 仿真计算了热障涂层厚度为400 μm、 裂缝长边方向平行于矩形波导探头长边的不同宽度的裂缝。结果表明: 热障涂层厚度不同时, 微波检测金属表面裂缝的敏感工作频率不同; 裂缝方向与波导口长边的夹角为50°～55°时检测敏感度低。裂缝宽度小于8 μm时用本研究中的频率范围无法检测, 裂缝宽度在10～30 μm时检测效果不明显, 裂缝宽度在30 μm～1 mm范围内, 裂缝越宽微波的反射系数相位差越大。因此, 在合适的工作频率下能利用微波无损检测技术对热障涂层下金属表面的裂缝进行无损检测。
关键词:
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微波无损检测
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热障涂层
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金属
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裂缝
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相位差
Abstract:
Based on the propagation characteristics of microwave and the microwave sensitivity to the interface, the phase difference at the interface of thermal barrier coating(TBC) and waveguide probe was used to characterize the long crack on the metal substrate surface under TBC using computer simulation technology-microwave studio (CST-MWS). The influences of top coating thickness and crack direction were studied. Besides, microwave evaluation of cracks with different width and the crack length direction parrallel to the long brim of the rectangular waveguide probe were studied when the thickness of TBC is 400 μm. The results show that the top coating thickness affects the sensitive frequency, and that the carck direction influences the evaluation sensitive, and the evaluation sensitive is the minimum when the angle between the rack length direction and the long brim of the rectangular waveguide probe is 50°-55°. It is also observed that the crack can not be detected when the crack width is less than 8 μm, and the effect of detection is not obvious when the crack width is 10-30 μm, and the wider the cracks, the greater the phase difference of the reflection coefficient when crack width is in the range of 30 μm-1 mm. Therefore, it is feasible to evaluate the crack on the metal substrate surface using microwave non-destruction evaluation.
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