Fractographic Analysis of High-Cycle Fatigue in Aircraft Engines
Final technical rept. 15 Jul 1998-31 Dec 1999
SRI INTERNATIONAL MENLO PARK CA
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A seedling program was conducted to determine whether load information is stored in the fracture surface features of failed aircraft components and, if so, to explore methods for extracting this information. Fracture surfaces produced under systematically varied cyclic load conditions in laboratory specimens of titanium turbine blade alloy were provided to the program by an aircraft engine manufacturer. Three-dimensional topographs of the surfaces were obtained via confocal optics and microscopy and analyzed with Fourier and wavelet techniques. Both analysis techniques confirmed the existence of load information in the fracture surface topography. Moreover, correlation was found between Fourier results and fatigue load parameters. The topographic characterization and analysis method was then applied to an F-118 engine component that had cracked in service to determine whether the load history that caused the cracking could be extracted. Using the results from the laboratory specimens as a reference database, the method provided a quantitative estimate of an influential fatigue load parameter and indicated its variation with crack growth distance.
- Fabrication Metallurgy