Quantitative Measurement of Defect Depth Using Pulsed Thermography: A Comparative Study

The detection of defects within a material is a vital research area. The popular and effective quantitative prediction technique widely used is pulsed thermography (PT). Therefore, based on the relationship between depth and particular time, namely specific characteristic time (SCT), many methods have been reported in the literature. In this paper, a comparison between the use of five methods, namely: peak contrast time (PCT), peak slope time (PST), absolute peak slope time (APST), logarithmic peak second-derivative (LPSD), and early detection (ED) for the detection of defects in the composite material is presented. First, a brief theoretical modeling of the thermographic process associated with an infrared technique of each method is described. Then, numerical and experimental cases are performed in which the results are analyzed and compared. Regardless of the processing time, the PST, APST, and LPSD methods appear to be accurate in determining depth. Nevertheless, the TSR method coupled with ED approach is preferable and particularly interesting provided that the studied area is properly identified.