Using a mobile photothermal probe we show that it is possible to detect rapidly different type of cracks (emerging ones or not), their width being a few micrometers and their depth being some hundredths of micrometers.

Among the non-destructive techniques, testing methods using thermal waves are starting to be developed in industry. Photothermal radiometry under cw excitation, which is one of these methods, has been used in this work for the detection of wear cracks, either emerging on the surface of the sample or covered with a thin layer. Before conducting the experimental study, we have developed a three-dimensional mathematical model. It is shown that the influence of the flaw on the photothermal signal is indeed the result of two phenomena: a thermal barrier effect and an optical effect owing to the higher emissivity of the crack when it is emerging.

Based on a previous experimental and theoretical study /1, 2/, we describe here a new method for the characterization of the thermophysical and structural parameters of the upper layer and/or the interface of semitransparent bilayered materials (thickness 1, thermal contact resistance R, thermal diffusivity α, absorption coefficient β).