Abstract:
Active thermal non-destructive testing (TNDT) has emerged as a swift,
robust and cost-effective non-contact inspection method used to
detect the surface and sub-surface defects present in a wide verity of
solid materials. To further increase the efficacy of the process,
various pulse-compression-based post-processing techniques are in
use. However, the applicability of pulse compression-based thermographic methods has limited due to the presence of side lobes that
degrades the energy concentration capabilities within the main lobe.
In order to address this limitation, this work proposes a poly-phase
code (P4-code). P4 codes are very efficient and robust in the reduction
of distribution of energy in side lobes by concentrating on the main
lobe. This Letter proposes a numerical study on the applicability of
P4 codes-based pulse compression favourable thermal wave imaging
approach for TNDT for testing and evaluation of steel specimen for
identification of flat-bottom hole defects located at different depths.
Further performance of the proposed method is compared with
the widely used linear frequency modulated thermal wave imaging
by considering the signal-to-noise ratio as a figure-of-merit.
