An extensive review of probabilistic techniques in fatigue analysis indicates that
there is a need for new microstructure-sensitive methods in describing the effects
of notches on the fatigue life reduction in cyclically loaded components. Of special
interest are notched components made from polycrystalline nickel-base superalloys,
which are used for high temperature applications in aircraft gas turbine engine disks.
Microstructure-sensitive computational crystal plasticity is combined with novel probabilistic
techniques to determine the probability of failure of notched components
based on the distribution of slip within the notch root region and small crack initiation
processes. The key microstructure features of two Ni-base superalloys, a fine and
coarse grain IN100, are reviewed and the method in which these alloys are computationally
modeled is presented. Next, the geometric model of the notched specimens
and method of finite element polycrystalline reconstruction is demonstrated. Shear-based
fatigue indicator parameters are used to characterize the shear-based, mode I
formation and propagation of fatigue cracks. Finally, two different probabilistic approaches
are described in this work including a grain-scale approach, which describes
the probability of forming a crack on the order of grain size, and a transition crack
length approach, which describes the probability of forming and propagating a crack
to the transition crack length. These approaches are used to construct cumulative
distribution functions for the probability of failure as a function of various notch root
sizes and strain load amplitudes.
| Identifer | oai:union.ndltd.org:GATECH/oai:smartech.gatech.edu:1853/34704 |
| Date | 18 May 2010 |
| Creators | Musinski, William D. |
| Publisher | Georgia Institute of Technology |
| Source Sets | Georgia Tech Electronic Thesis and Dissertation Archive |
| Detected Language | English |
| Type | Thesis |
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