| Development of crack in materials can cause structure break, and result in massive disastrous accidents. The initially microcrack is difficult to be detected.Furtherly, the existed detection methods have some disadvantages such as outside interference, low detection accuracy and narrow range of applications. QDs have narrow fluorescence wavelength and wide excitation spectrum, high luminescence intensity and long-term stability without optical bleaching. These advantages indicate that QDs are quite suitable for crack monitoring. In this thesis, the fatigue crack of ceramic coating and bulk have been detected.The relationship between luminescence intensity and ceramic thickness is studied by confocal microscope and spectrometer. Moreover, to obtain the regularity between luminescence intensity and stress distribution, stress distribution of Al2O3ceramics are simulated by Ansys software. The relationship between luminescence intensity and stress with variety of specimen thickness is obtained. The main results are listed as follows:(1)A monitoring system for micro fatigue crack of ceramics based on QDs is set up. Fatigue crack is generated after making QDs film on specimen, then an obvious bright line was observed corresponding to crack under ultraviolet light. The actual width of crack on ceramic observed by microscope is close to the width detected by luminescence. The error is just about2%.Micro fatigue crack can realize a real-time monitoring via QDs.(2)The change of luminescence intensity on the same point at different temperature is studied. Relative luminescence intensity is found decrease obviously with temperature. With the increasement of temperature to50℃, time stability is still quite well.(3)A relationship between luminescence intensity and stress is built as ystress=0.00761Xintensity-187.05. With the change of thickness of ceramic, both luminescence intensity and stress show increasing with the decreasing of ceramic thickness. |
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