12 October 2010 Quantitative detection of defect using ultrasound infrared lock-in thermography
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Ultrasound infrared lock-in thermography (ULT), which uses ultrasonic wave to excite surface of a sample and lock-in method to analyze thermal image sequence, and it is an active infrared thermography for non-destructive testing. This technique can be used to detect crack, impacted damage in metal or ceramic material, and some typical defects of composite, such as disbanding, delamination. Amplitude modulated ultrasound, which is injected into the sample and converted into heat mainly in defects or areas with stress concentration. The generating heat travels to the surface by conduction. Thermal image sequences which express surface temperature changing are obtained by an infrared camera and processed by lock-in method to obtain phase image and amplitude image. Phase contrast and amplitude contrast between defective area and sound one are used to indentify defects. In this paper, the theory and method of processing thermal image sequence are researched based on the ULT. Experiments are carried out on a metal plane with surface's micro-cracks for verification. It is obtained that the relations between geometric parameter of defect and the phase contrast or the amplitude contrast at different inspecting parameters. A method of quantitative detection defects is proposed by ULT.
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Hui Liu, Hui Liu, Junyan Liu, Junyan Liu, Yang Wang, Yang Wang, } "Quantitative detection of defect using ultrasound infrared lock-in thermography", Proc. SPIE 7656, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 76566E (12 October 2010); doi: 10.1117/12.867987; https://doi.org/10.1117/12.867987

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