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12 April 2004 The thermal photocopier: a new concept for thermal NDT
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Abstract
The thermal line scanner has proven to be a successful method of rapidly scanning large areas of aircraft fuselage for delaminations and metal pipes for corrosion. The limitation of this technique is with the finite depth by which flaws can be located due to the fixed distance that the thermal camera follows the moving line source. To identify deeper flaws within a material, the thermal imager and line source must have a greater separation distance so that the heat has more time to propagate through the material. Ultimately, one would want to identify flaws at any depth requiring continual scans with greater separation between the line source and imager. The Thermal Photocopier is a hybrid of the thermal line scanner. It utilizes a moving line source and a stationary infrared camera. Any one image captured by the computer shows the sample in gradient cooling due to the moving heat source. An algorithm has been developed that reconstructs full-field images of the material at specific cool down times. These frames represent various depths into the sample as the heat propagates through the thickness of the material. Therefore, an object can be analyzed from the front to the back surface for flaws using this modified thermal detection system. This system has been tested on aluminum and composite materials of varying thickness yielding results consistent with thermographic images obtained with flash and quartz lamps.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Deonna F. Woolard and K. Elliott Cramer "The thermal photocopier: a new concept for thermal NDT", Proc. SPIE 5405, Thermosense XXVI, (12 April 2004); https://doi.org/10.1117/12.541881
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