Abstract
We have investigated the technique to detect acoustic emission (AE) signal using a laser interferometer, which can directly detect the surface velocity due to microcracking. Thermal cycle test for Al2O3/NiCrAlY/SUS304 coatings using an infrared image furnace was carried out in order to evaluate the failure process. Laser AE measurement system was improved to increase the sensitivity of AE monitoring for coatings. Microfracture mode during thermal cycle test was analyzed based on the measured AE behavior and a finite element method (FEM) simulation of wave propagation. From the result of waveform analysis, it was found that shear mode microfracture occurred toward the center from one of the edges of the specimen. This result agreed with the propagation direction of delamination determined from AE location results and the observation of the specimen after the thermal cycles were loaded.
