The Development of Photo-stimulated Luminescence Spectroscopy for 3D Stress Measurements in the Thermally Grown Oxide Layer of Thermal Barrier Coatings

摘要

The development of photo-stimulated luminescence spectroscopy (PSLS) for stress measure- ment in chromium-doped alumina has been motivated by the need for a non-destructive technique to establish the integrity of the thermally grown oxide (TGO) layer on turbine blades of jet engines. Applications of PSLS have been based on two spectral peak positions (R-lines) and their stress dependence has been fully exploited for planar measurements. However, factors associated with the oxide layer such as its undulated nature and growth stresses emphasize the need to measure other stress components unavailable with the planar model in use today. Our new ndings on the piezo-spectroscopic (PS) nature of vibronic bands in the optical spectrum of chromium-doped alumina pave the way for a 3-D model of stress measurement never before established. The focus of this research is on developing the PSLS technique to measure 3-D stresses by studying the piezospectroscopic behavior of these less explored parameters through compression tests. Together with the R lines, the PS coe cients of peaks within the vibronic bands form the spectral parameters for our 3D stress measurement model. This will provide a more exact stress-prediction method in non- destructive testing of the TGO and eventual life prediction of the thermal barrier coatings of aircraft engine turbine blades.