Defect Recognition in Thermosonic Imaging

This work is aimed at developing an effective method for defect recognition in thermosonic imaging. The heat mechanism of thermosonic imaging is introduced, and the problem for defect recognition is discussed. For this purpose, defect existing in the inner wall of a metal pipeline specimen and defects embedded in a carbon fiber reinforced plastic (CFRP) laminate are tested. The experimental data are processed by pulse phase thermography (PPT) method to show the phase images at different frequencies, and the characteristic of phase angle vs frequency curve of thermal anomalies and sound area is analyzed. A binary image, which is based on the characteristic value of defects, is obtained by a new recognition algorithm to show the defects. Results demonstrate good defect recognition performance for thermosonic imaging, and the reliability of this technique can be improved by the method.