About this Abstract |
| Meeting |
11th International Symposium on Superalloy 718 and Derivatives 2026: Legacy, Innovations, and Future Directions
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| Symposium
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Superalloy 718 and Derivatives 2026: Legacy, Innovations, and Future Directions
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| Presentation Title |
New approach for characterizing cyclic crack growth by loading, unloading, reloading testing |
| Author(s) |
Andreas Hausmann, Bodo Gehrmann, Masood Hafez Haghighat, Heinz Werner Höppel, Steffen Neumeier |
| On-Site Speaker (Planned) |
Andreas Hausmann |
| Abstract Scope |
A novel testing approach for cyclic crack growth characterization is presented, enabling faster data generation at both room and elevated temperatures. This is particularly relevant for superalloys, which are used in critical high-temperature applications such as turbine engines, where fatigue cracks can lead to sudden failure. Due to their complex microstructures, superalloys are especially sensitive to crack initiation and propagation, requiring accurate and efficient fatigue life prediction methods.
Conventional fatigue crack growth tests using compact tension or corner crack specimens under constant load amplitude are often time-consuming. In contrast, the new method employs single-edge notched bend (SEN(B)) specimens following ASTM E1820, with cyclic loading, unloading, and reloading at a constant stress rate. The maximum stress increases incrementally with each cycle until fracture.
At each maximum loading reversal point, the differential elastic modulus (ED) is determined. Progressive crack growth reduces load-bearing cross-section and leads to an additional decrease in ED.In this context, the stress dependence of elastic stiffness of undamaged state ED0 must be considered. The ratio of ED⁄ED0 estimation of crack length and reduction in cross-sectional area over time.
Stress intensity factors are calculated according to ASTM E1820, and cyclic crack growth rates (da/dN) are derived and plotted against the stress intensity range (∆KI), producing classic fatigue crack growth curves. Initial tests demonstrate strong potential for accelerated material screening. Further validation is underway using Alloy 718, a well-characterized nickel-based superalloy. |
| Proceedings Inclusion? |
Definite: At-meeting proceedings |