Brazing joining is widely used in heat exchangers due to its effectiveness in increasing the efficiency of the heat-exchange process. When there is a defect in the brazing joints of a heat exchanger, damage occurs to the heat exchanger and heat efficiency is decreased. Therefore, to secure the quality of the brazing joints, the development of a highly reliable inspection method that can detect the defects in the brazing joints is required. We utilize an x-ray-using method to inspect the defects in brazing joints. First, x-ray cross-sectional images of the brazing joints are obtained by using computerized tomography (CT) technology. A cross-sectional image obtained from CT is more effective to detect the inner defects than the traditional transmitted x-ray image. Second, the acquired images are processed, and then template-matching-based defect detection algorithms of the brazing joints are proposed. Finally, a series of experiments to detect the brazing defects by using the proposed algorithm are performed concerning two types of brazing joint. The experimental results show that the proposed algorithms are suitable for defect detection of the brazing joint-based heat exchangers.
"Template-based defect detection of a brazed heat exchanger using an x-ray image," Optical Engineering 52(3), 036501 (4 March 2013). https://doi.org/10.1117/1.OE.52.3.036501