Determining position of cracks on polished stone surfaces using flash active thermography

This paper presents a novel application of active thermography for determining the positions of surface reaching cracks at polished stone slabs. The use of both a visual and a thermal camera, after calibration, allows us to overlap the results of the thermal analysis over visual images. A commercially available plate was used for calibration of cameras. The overlapping of the images enables us to plan more efficiently the cutting process, decreasing the waste and allowing us to choose the most desirable surface texture to become the part of the final product. The method allows us to reckon the direction of the crack inclination beneath the polished surface, based on the analysis of temperature distribution in proximity to the crack. A FEM analysis, which clarifies the temperature distribution in the surrounding of inclined crack, was presented.