Implementation of frequency-modulated thermal wave imaging for non-destructive sub-surface defect detection

Thermal non-destructive testing (TNDT) is a whole field and non-contact technique for defect detection. The present work describes a variant of TNDT for subsurface defect detection based on frequency modulated thermal wave imaging (FMTWI). Use is made of the frequency dependence of thermal diffusion length, to achieve entire depth scanning of a sample in one run. This novel technique overcomes some of the drawbacks associated with traditional pulse and lock-in thermography. Experimental results are presented in support.