The detection of small cracks on a steel surface using eddy current pulsed thermography


Small defects in steels often lead to catastrophic accidents, and cracks are one of common defects in steel materials. For the small cracks on the surface of the steel plate, the late-model eddy current pulsed thermography (ECPT) method was used for testing research. It has many advantages, such as non-contact measurement, high sensitivity, large detection area, intuition, high precision and so on. In this paper, a finite element model of the edge typical defects on the metal components is built. The heat transfer of the sample during the whole heating process, the temperature distribution of the sample surface and the crack boundary were analyzed based on the model. Under the condition of different depth and width, the change rule of the temperature at the crack is analyzed. The experimental platform was built to verify the reliability of the simulation results and carried out the experimental study of crack detection. Through the analysis of the original thermal image, the defects can be observed quickly and clearly, and the quantitative identification of crack length and depth can be achieved. The results show that the defect is always the highest area of the whole sample temperature. The maximum temperature of the defect increases with the growth of the defect depth, and decreases with the growth of the defect width. The testing technology of ECPT can effectively detect cracks and small defects by analyzing the temperature changes on the surface of the sample, and can perform more accurate quantitative analysis of defects through feature extraction and data processing.