Active infrared thermography (IRT) has been used to detect delamination on yttria-stabilized zirconia thermal barrier coatings (YSZ-TBC) using various heat sources. Thermal shock tests were performed to induce delamination on 1x1 inch flat samples. Each thermal cycle consisted of heating the samples in a muffle furnace, holding at 1020°C for 5 minutes, and quenching on water at approximately 20°C. Two samples were used, the first was brought to failure (184 cycles) and the second was almost intact to the naked eye (100 cycles). In addition to these samples, a discarded gas turbine blade was cut, and a delaminated fragment was used for comparison. IRT was performed using two 600 W flash lamps, one 500 W halogen lamp, and a long-wave infrared camera with a frame rate of 30 Hz. The acquired signal was first processed by the Thermal Signal Reconstruction (TSR) method using a 4th order polynomial interpolation and its first and second time derivatives. The thermographic data were processed using the Principal Component Analysis (PCA) algorithm. PCA was applied to both raw and pre-processed data. The results were compared using signal-to-noise ratio (SNR) to measure the quality of the algorithms used to detect delaminated areas. The comparisons showed that PCA results are improved when applied to the TSR sequences. However, the selection of the principal component with the highest SNR depends on the heating condition (flash or long pulse) and on the samples analyzed.
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