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Materials Science and Engineering, University of Michigan

  MSE / Research / Projects / Rapid Assessment of the Role of Microstructural Variability in the Fatigue Behavior of Superalloys Using Ultrasonic Fatigue

Rapid Assessment of the Role of Microstructural Variability in the Fatigue Behavior of Superalloys Using Ultrasonic Fatigue
Collaborators: J.W. Jones, University of Michigan
Materials: Metals
Application: Structural
Technique: Characterization

The objective of this research program is to conduct a critical investigation of the capabilities of ultrasonic fatigue techniques in life prediction of nickel base superalloys. With DARPA support we will investigate the role of microstructure variability on the fatigue behavior of superalloy turbine disk and blade materials. This research is in collaboration with Professor J.Wayne Jones (Michigan) and Dr. James Larsen, Air Force Research Laboratories.

A three-year program will accomplish the following tasks:

1. Examine fatigue behavior for a polycrystalline nickel-base superalloy to develop a statistically significant database of fatigue behavior for carefully chosen test conditions (stress range, mean stress, temperature). Fatigue behavior (stress vs. cycles to failure) will be investigated in the range of 105 to 109 cycles using ultrasonic fatigue instrumentation and the capability of this approach for high temperature fatigue crack growth from small notches and similar defects will be determined.

2. Develop statistically significant correlations between local microstructure characteristics and crack propagation behavior through quantitative imaging of serial sections, fractography and related techniques. We anticipate a strong collaboration here with ongoing efforts at AFRL and significant use of strain mapping techniques to develop a better understanding of strain localization near defects.

3. Couple these findings with quantification of microstructural variability in collaboration with the Air Force Research Laboratory to improve existing models or to develop new approaches to modeling the role of microstructure on fatigue behavior and to examine the potential of ultrasonic fatigue as a means of rapidly assessing critical microstructural features that lead to fatigue failures from defects at elevated temperatures.
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