Fatigue Reclamation: The Concept of Self-Healing.
ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
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A simple analytical model for predicting the onset of fatigue crack initiation bas been developed. The models usefulness is based on the premise that if a component can be removed from service before fatigue crack initiation and thermally heat treated to remove any accumulated fatigue damage, it can be placed back in service and periodically heat treated to extend its life. Three point bend specimens with semicircular notches were machined from A723 steel, isothermally processed in molten salts to predetermined strength and toughness levels, and fatigue tested in the extreme low cycle fatigue region. Because of negative preliminary findings, the concept of reclamation fatigue in the extremely low cycle fatigue regime does not appear to be a viable means for extending the overall life of components. Although technically correct, the model did not accurately predict the onset of crack initiation. The study also suggests that, although cracking was not observed in all specimens, some damage could not be eliminated by thermal treatment. Because most point defects will be eliminated by thermal treatment, it is believed that nondetectable microscopic crack growth had occurred.
- Numerical Mathematics