A New Approach Towards Characterizing Microstructural Influence on Material Behavior Under Very High Cycle
Technical Report,01 Sep 2012,31 Aug 2015
UNIVERSITY OF MICHIGAN ANN ARBOR United States
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Very high cycle fatigue VHCF, in which components undergo fatigue lifetimes well beyond traditional design limits of 107 cycles, is not well understood and is becoming an increasingly prevalent deformation state in aerospace applications. Components are now designed to handle increasingly long lifetimes 109cycles, and it is critically important to be able to accurately predict when these components will fail and to intelligently tailor them for improved performance. Toward this end, a new methodology was developed for the small-scale investigation of fatigue crack initiation and growth during VHCF loading, and was used to investigate environmental and microstructural effects on the fatigue lifetimes of the polycrystalline titanium alloy Ti-6242S. Small fatigue crack growth in Ti-6242S, a commonly utilized alloy in aerospace applications, was examined in vacuum and in controlled partial pressures of water vapor, high purity oxygen, and high purity hydrogen.