Research on Debonding Defects in Thermal Barrier Coatings Structure by Thermal-Wave Radar Imaging (TWRI)
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In this paper, thermal-wave radar imaging (TWRI) is introduced to detect debonding defects in SiC-coated Ni-based superalloy plates. Linear frequency modulation signal (chirp) is used as the excitation signal which has a large time–bandwidth product. Artificial debonding defects in SiC coating are excited by the laser beam with the light intensity modulated by a chirp signal. Cross-correlation algorithm and chirp lock-in algorithm are introduced to extract the thermal-wave signal characteristic. The comparative experiment between TWRI reflection mode and transmission mode was carried out. Experiments are conducted to investigate the influence of laser power density, chirp period, and excitation frequency. Experimental results illustrate that chirp lock-in phase has a better detection capability than other characteristic parameters. TWRI can effectively detect simulated debonding defects of SiC-coated Ni-based superalloy plates.
KeywordsChirp signal Debonding defects Thermal barrier coating Thermal-wave radar imaging
This work was supported by the Foundation for Innovative Research Groups of the National Nature Science Foundation of China under Grant No. 51521003, the Chinese National Natural Science Foundation under Contract Nos. 61571153, 51173034, Self-planned Task of State Key Laboratory of Robotics and System (HIT), and the Programme of Introducing Talents of Discipline of Universities (Grant No. B07108) for the research support.
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