20 November 2012 Continuous turbine blade creep measurement based on Moiré
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Abstract
Moiré imaging has been used to measure creep in the airfoil section of gas turbine blades. The ability to accurately assess creep and other failure modes has become an important engineering challenge, because gas turbine manufacturers are putting in place condition-based maintenance programs. In such maintenance programs, the condition of individual components is assessed to determine their remaining lives. Using pad-print technology, a grating pattern was printed directly on a turbine blade for localized creep detection using the spacing change of moiré pattern fringes. A creep measurement prototype was assembled for this application which contained a lens, reference grating, camera and lighting module. This prototype comprised a bench-top camera system that can read moiré patterns from the turbine blade sensor at shutdown to determine creep level in individual parts by analyzing the moiré fringes. Sensitivity analyses and noise factor studies were performed to evaluate the system. Analysis software was also developed. A correlation study with strain gages was performed and the measurement results from the moiré system align well with the strain gage readings. A mechanical specimen subjected to a one cycle tensile test at high temperature to induce plastic deformation in the gage was used to evaluate the system and the result of this test exhibited good correlation to extensometer readings.
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Yi Liao, Yi Liao, Robert Tait, Robert Tait, Kevin Harding, Kevin Harding, Edward J. Nieters, Edward J. Nieters, Wayne C. Hasz, Wayne C. Hasz, Nicole Piche, Nicole Piche, } "Continuous turbine blade creep measurement based on Moiré", Proc. SPIE 8563, Optical Metrology and Inspection for Industrial Applications II, 85630H (20 November 2012); doi: 10.1117/12.2000283; https://doi.org/10.1117/12.2000283
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