Thermal barrier coatings (TBCs) are crucial for protecting high-temperature components in gas turbines and aeroengines. However, conventional non-destructive testing (NDT) methods, such as infrared thermography, face challenges in precisely detecting and quantifying debonding defects due to limitations in imaging contrast and sensitivity to surface states. In this work, a novel scheme for imaging debonding defects in TBCs using grating laser acoustic spectroscopy is proposed. The scheme, validated by numerical simulations and experimental results, is the first to introduce the mode conversion mechanism of Rayleigh and Lamb waves in the field of TBCs, achieving noncontact photoacoustic imaging of debonding defects for the first report. The all-optical laser ultrasonics system generates velocity maps with enhanced contrast and immunity to surface states, outperforming infrared thermography. Threshold segmentation precisely outlines defect contours, enabling precise quantification of defect size with an error below 5%. This work demonstrates a noncontact, precise, high-contrast imaging and surface-state-immune technique for evaluating the integrity and durability of TBCs, with potential applications in engineering.

中文翻译：

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光栅激光声谱热障涂层的脱粘缺陷成像


热障涂层 （TBC） 对于保护燃气轮机和航空发动机中的高温部件至关重要。然而，由于成像对比度和对表面状态的敏感性的限制，传统的无损检测 （NDT） 方法（如红外热成像）在精确检测和量化脱粘缺陷方面面临挑战。在这项工作中，提出了一种利用光栅激光声谱对 TBC 中脱粘缺陷进行成像的新方案。该方案经过数值模拟和实验结果验证，首次在TBC领域引入瑞利波和兰姆波的模式转换机制，首次实现了脱粘缺陷的非接触式光声成像。全光学激光超声波系统生成的速度图具有增强的对比度和对表面状态的免疫力，性能优于红外热成像。阈值分割可精确勾勒出缺陷轮廓，从而能够精确量化缺陷大小，误差低于 5%。这项工作展示了一种非接触式、精确、高对比度的成像和表面状态免疫技术，用于评估 TBC 的完整性和耐用性，在工程中具有潜在的应用。