We apply lock-in infrared thermography with homogeneous illumination to characterize semi-infinite delaminations (infinite in one direction but with finite length in the perpendicular direction), i.e., we determine the delamination depth, length and thickness. We present two independent calculations of the surface temperature amplitude and phase: a semi-analytical solution by applying the cosine Fourier transform and the quadrupoles method, and a numerical calculation using finite element modelling. The sensitivity analysis indicates that both amplitude and phase data are required to obtain the three parameters (depth, length and width of the delamination) simultaneously. By fitting experimental data taken on AISI-304 stainless steel samples containing calibrated delaminations of different lengths and widths and located at different depths, we prove that it is possible to characterize semi-infinite delaminations with lock-in IRT.
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