Abstract
A hybrid specimen was developed to minimize material used when assessing bending fatigue behavior with a vibration-based experimental procedure. Motivation for this work comes from the eagerness to quantify critical three-dimensionally printed gas turbine engine components at low cost under representative operating and stress conditions. The original vibration-based fatigue specimen (a whole, square plate) is capable of providing airfoil representative data at a lower cost than failing a fully manufactured airfoil. The reduced cost, though significant, was further reduced with the hybrid specimen. The most recently published iteration of the hybrid specimen produced an insert-plate system that required 95 % less material than the original specimen in order to gather fatigue data, and the hybrid specimen data compared favorably within a 95 % prediction interval of the original for Aluminum 6061-T6. Despite the successful comparison, improvements to the hybrid plate specimen were still necessary for accurately assessing fatigue behavior of more commonly used aerospace alloys. Specifically, improving repeatability in the experimental response, increasing the hybrid specimen excitability (i.e. reduce specimen system damping), and minimizing damage accumulation on the carrier plate of the hybrid specimen were critical to the efficiency of the characterized bending fatigue behavior. The proposed investigation addressed these issues for Titanium 6Al-4V, resulting in a more repeatable experimental procedure and results that agree with whole plate data.
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Abbreviations
- A :
-
Stress-life regression parameter
- B :
-
Stress-life regression intercept
- g :
-
Gravitational constant (9.81 m/s2)
- N fail :
-
Number of cycles to failure
- N step :
-
Number of cycles per step
- με a :
-
Microstrain amplitude
- σ a :
-
Stress amplitude
- σ fail :
-
Stress amplitude during failed step
- σ pr :
-
Stress amplitude during previous step
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Acknowledgements
The authors would like to thank the following organizations for funding and collaboration: the Turbine Engine Fatigue Facility (TEFF) of the United States Air Force Research Laboratory (AFRL) and Universal Technology Corporation (UTC). Specifically, the authors would like to acknowledge UTC contractors Phil Johnson, Jeff Bruns, and Alyssa Zearley for their contribution to specimen and fixture design and analysis, as well as laboratory testing and experimentation setup.
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Scott-Emuakpor, O., George, T., Holycross, C., Cross, C. (2017). Improved Hybrid Specimen for Vibration Bending Fatigue. In: Zehnder, A., et al. Fracture, Fatigue, Failure and Damage Evolution, Volume 8. Conference Proceedings of the Society for Experimental Mechanics Series. Springer, Cham. https://doi.org/10.1007/978-3-319-42195-7_4
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DOI: https://doi.org/10.1007/978-3-319-42195-7_4
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