Modeling of Pulsed Thermography in Anisotropic Media

In a previous paper [4], a simple model was developed (referred to as Modell) to describe the surface temperature evolution of a 1/8" thick aluminum panel with fixed I" diameter flat bottom holes of different depth in response to a short pulse of radiant energy. That model correctly described the temporal behavior of alii" flat bottom holes. To further validate Model I, a new panel was fabricated (Fig 1) that contained flat bottom holes of different diameters and different depths. After careful analysis of the data, it was found that Model I could not adequately account for the new experimental results. In this paper a new model is introduced (referred to as Model II) that accurately describes the experimental data. The main difference between the models is the way in which thermal conductance is treated. In Model I the thermal conductance was approximated by an effective contact conductance (K=k,;A where kc is a contact conductivity and A is the cross sectional area). In Model IT the thermal conductance is approximated by an effective thermal conductivity (K=k"Afl where k is the thermal conductivity and I is a characteristic length).