A normalization procedure for pulse thermographic nondestructive evaluation

• A new normalization procedure for interpreting results of pulse TNDE is proposed.
• TNDE results become simpler and material independent after normalization.
• Scaling issues in correlating experimental and numerical results are eliminated.
• Normalized results provide direct estimation of defect depth.

Pulse thermographic nondestructive evaluation (TNDE) technique can be used to estimate defect dimensions, and in particular the depth at which the defect is located. Numerical models of this procedure can aid in the interpretation of experimental results. However, the thermophysical properties of the test object as well as the amount of energy absorbed during this process are not readily available for such models. This paper presents an extension of the thermographic signal reconstruction (TSR) procedure in which the temperature and the time scales are respectively normalized with equilibrium temperature and the break time. In the normalized form these profiles are independent of material properties and instrumentation settings. Thus in the normalized format, experimental results can be readily compared with numerically generated thermographic results. The defect depth can also be easily obtained as a fraction of plate thickness from this plot.