Development of Thermographic NDTTechnique Based on Lock-in Measurement of Thermal Wave Response for Structural Integrity Assessment of Aging Aircraft

本项目开发了一种新的定量无损检测（NDT）技术，用于老化飞机的结构完整性评估。主要研究结果如下：1.为了检测裂纹，利用锁相热成像技术测量了周期调制电流作用下裂纹尖端的奇异电场。实验研究了该方法在钢和铝合金板裂纹识别中的分辨率和适用性。在模具锁定热图像中，在裂纹尖端观察到显著的奇异磁场。准确地确定了裂纹的位置和尺寸，证明了该技术的可行性.针对材料损失和分层缺陷，提出了一种基于周期加热下表面温度锁定测量的热成像无损检测技术。实验研究了该方法对扁平B类缺陷检测的适用性 关于我们 底孔缺陷和分层缺陷。通过锁相热成像仪拍摄同相和异相温度幅值图像，与周期性加热的参考信号同步。在此基础上，提出了一种基于脉冲加热下瞬态温度的热像无损检测技术。利用傅里叶级数分析了反映缺陷尺寸、形状和深度等参数的温降曲线。将所发展的技术应用于航空结构材料损伤和分层缺陷的识别。结果表明，所开发的红外热像无损检测技术可以准确地确定缺陷参数.提出了一种基于锁相红外热成像相位延迟测量的混凝土结构分层缺陷定量无损检测技术。通过对比度变化可以估计缺陷的位置和大小，通过相位延迟与加热时间的关系可以估计缺陷的深度.被动电位CT法是近年来发展起来的一种新的监测技术。利用反分析法对粘贴在结构上的压电薄膜表面的电位分布进行了测量。少

The present project developed a new quantitative nondestructive testing (NDT) technique for structural integrity assessment of aging aircrafts. The results obtained are summarized as follows.1. For detecting cracks, singular electrothermal field near crack tips under the application of periodically modulated electric current was measured using lock-in thermography. Experimental investigations were made on the resolution and the applicability in the identification of cracks embedded in steel and aluminum alloy plates. Significant singular electrothermal field was observed at the crack tip in die lock-in thermal image. Location and size of the crack were accurately determined, demonstrating the feasibility of the proposed technique.2. For material loss defects and delamination defects, a thermographic NDT technique based on the lock-in measurement of the surface temperature under periodical heating was developed. Experimental study was made on the applicability to the detection of flat b … More ottom hole defects and delamination defects. In-phase and out-of-phase temperature amplitude images were taken by the lock-in thermography, synchronized to the reference signal of the periodical heating. Further, another thermographic NDT technique based on the transient temperature under the pulse heating was developed. Temperature descent curve which reflects defect parameters such as size, shape and depth of defects was analyzed using Fourier series. Developed techniques were applied to the identification of material loss defects and delamination defects in aerospace structures. It was found that defect parameters can be accurately determined by the developed thermographic NDT techniques.3. Quantitative NDT technique for delamination defects in concrete structures was developed based on the phase delay measurement using a lock-in infrared thermography. Location and size of the defect can be estimated from the contrast change and depth can be estimated from the relationship between phase delay and heating period.4. Passive electric potential CT method was developed as a new monitoring technique. Electric potential distribution measurement on the surface of piezoelectric film glued on the structure was processed by inverse analysis. Less