Depth feature extraction of surface-breaking defects using laser pulsed thermography

Abstract

In this paper, the feasibility of the depth feature extraction of surface-breaking defects based on laser pulsed thermography in transmission mode is proposed. This method is adopted to detect the depth of surface-breaking defects. First, a finite element model based on COMSOL is established to simulate structural steel specimens with different defect depths and the contrast method is used to detect these depths. In order to verify its feasibility, the model is simulated at different time nodes. A simulation analysis shows the practicability of this method. Then, through an artificial slot depth feature extraction experiment on structural steel specimens, an algorithm is used to denoise an infrared image and then the contrast method is used to extract the defect depth feature, which verifies the feasibility of the method. The experimental results show that as the depth of artificial slots increases, the temperature at the observation point also reduces. The best fitting equation of the defect depth and the temperature at the observation point at a certain heating time have an exponential relationship. This method can accurately detect defect depths.