Numerical Estimation of the Spatial Resolution of Thermal NDT Techniques Based on Flash Heating

In this paper we present a numerical method to quantitatively estimate the spatial resolution of a pulsed photothermal NDT system. We have simulated flash light heating applied to a delaminated plasma coated sample. The thermal parameters of the sample were chosen so that thermally the substrate material corresponds to steel and the coating layer corresponds to Cr2O3. The time-dependent three-dimensional diffusion equations resulting from the model were solved using Crank-Nicolson and implicit finite difference methods. Results of the calculations for different delamination sizes with different thermal contact resistances and the coating thicknesses of 50, 100, and 200 μm are presented. Also the time dependence of the sample surface temperature distribution is studied.