基于主动式热成像技术的埋藏式裂纹无损检测
Nondestructive Test for Buried Crack Based on Active Thermography Technique

钢材在服役过程中发生的埋藏式缺陷具有隐蔽性强、危害性大的特点，然而现有检测技术均无法实现对其在线检测。本文提出基于主动热成像技术和热图像序列主成分分析相结合的方法，研究其对盲孔和埋藏式裂纹的检测表现。测试结果表明，红外图像序列的第二主成分对于埋藏式缺陷的表征优于第一主成分；并且本文所述方法可以准确检出钢材表面2 mm以下的盲孔、裂纹等缺陷；尤其是对6 mm埋藏深度的裂纹，PCA第二主成分特征重构的图像对裂纹侧面轮廓表征优于5 mm埋藏深度的裂纹。因此，基于主动式热成像技术的无损检测方法可以实现对埋藏式缺陷的有效检出，为工程安全提供保障。
The hidden defects are undetectable and dangerous to steel in service. The existed measurement approaches cannot detect the hidden defects on-site. This paper provides an approach based on active thermography technique combined with principal component analysis for the thermal image sequence. The proposed approach is applied for blind hole and hidden cracks detection for validation. The test results indicate that the 2^nd principal component of thermal image sequence has better performance than the 1^st principal component for hidden defects. The proposed approach can accurately detect the blind hole and cracks which hide more than 2 mm under the sample surface. Especially, the 2^nd principal component re-constructed image for 6 mm depth crack has more explicit profile than the re-constructed image for 5 mm depth crack. Therefore, the provided nondestructive approach based on active thermography has the ability for hidden defects detection and engineering safety.