基于红外热成像的混凝土坝保温层缺陷检测方法

Infrared thermal imaging technique-based method for detecting defect of insulation layer of concrete dam

坝面保温层是保障高寒区混凝土坝长期安全运行的重要工程措施。紫外线照射会使保温层老化,削弱保温能力,引起坝体混凝土开裂,需要及时检测老化的保温层并进行修复。为此,基于红外热成像及图像处理技术,提出了一种非接触式的保温层缺陷快速检测方法。采用红外热像仪采集保温层表面热像图时间序列,对热像图序列进行二维傅里叶变换得到振幅图和相位图。根据像素点的所占比例和分布规律,采用K-means聚类方法对所得到的的振幅图和相位图进行聚类处理,以图像的方差筛选最优的振幅图和相位图,以此识别保温层缺陷。有限元模拟和两类保温层热成像试验的结果表明,这种非接触式的保温层缺陷快速检测方法能够准确地检测保温层中缺陷的大小和位置,可发展为一种适用于实际的混凝土坝保温层缺陷检测技术。

Insulation layer for dam surface is an important engineering measure to ensure the long-term safe operation of concrete dam in severely cold region. Ultraviolet radiation can cause the aging of the insulation layer and then weaken the insulation capacity and lead to the cracking of the concrete of dam body, the aging degree of the insulation layer is necessary to be detected and the relevant repairation must be made as well. Therefore, a method for non-contact rapid detection of the defect of the insulation layer is proposed herein based on the infrared thermal imaging and image processing technique. In this method, the thermal image time series of the insulation layer surface is collected by thermal infrared imager, and then two-dimension Fourier transform is made on the thermal image time series to obtain the relevant amplitude map and phase map. According to the proportion and the distribution law of the pixels, the clustering processing is carried out on the obtained amplitude map and phase map by means of K-means clustering, while the optimal amplitude map and phase map are screened out with the image variance for identifying the defect of the insulation layer. The results from finite element simulation and the two types of the thermal imaging experiment of the insulation layer show that this kind of the method for non-contact rapid detection of the defect of the insulation layer can correctly detect the size and location of the defect inside the insulation layer, and then can be developed into a technique that is suitable for detecting the defect of the insulation layer for concrete.