Abstract:
Among the various non-destructive testing and evaluation methods,
infrared thermography gained its importance due to its fast, whole
field, remote and quantitative evaluation capabilities for inspection of
various materials. Being an optimum technique in terms of usage of
low peak power heat sources in a moderate experimentation time,
frequency-modulated thermal wave imaging (FMTWI) plays a vital
role in the infrared thermographic community. The noise rejection
capabilities of the proposed pulse compression favourable FMTWI
by using principal component analysis as a post-processing technique
are highlighted. The proposed scheme has been tested on a mild-steel
sample having sub-surface flat bottom hole defects located inside the
test specimen at various depths. It is clear from the obtained results
that the reconstructed pulse (main lobe) concentrates much of the
imposed energy into a narrow duration, which enhances the defect
detection sensitivity and resolution in order to visualise the subsurface defects with higher signal-to-noise ratio
