Recognition of contact interface defect in metal plate based on pulsed phase thermography

Defect recognition is an important aspect to improve the efficiency of testing, reduce the manual workloads and the subjectivity of people´s judgments in Ultrasonic infrared thermography (UIRT). Aiming at the problem of low efficiency and poor ability on the contact interface defect recognition, the pulsed phase thermography (PPT) is studied in this paper. In the pulsed phase method (PPM), on the one hand, the temperature signals are transformed from time domain into frequency domain. On the other hand, the phase information, for example the phase image sequence, is obtained to judge different type of defect heating generation according to the thermal diffusion ability of different materials. Research results show that the surface defect and deep-seated defect can be judged from the phase image sequence, and the different thermal diffusions can be used to distinguish the crack from paint spots. This research aims to improve the veracity and validity of defect recognition for UIRT, and lay a theory foundation for the subsequent research.