Crack Tip Plasticity Associated with Corrosion Assisted Fatigue.
Abstract
Preliminary data is presented on the effect of a water vapor environment on the deformation within the plastic zone of fatigue cracks in 7075-T6. Results in the water vapor environment is compared to those in a vacuum environment. High spatial resolution observations have been made using a special cyclic stage for the SEM and strains have been determined using the stereoimaging technique. Crack tip opening is shown to be a power function of the distance behind the crack tip, in agreement with a theoretical derivation of this correlation. The crack tip strain correlates with the crack opening at 1 micrometer behind the crack tip. Crack tip strains are shown to vary considerably for a fixed cyclic stress intensity. By ignoring some data, a preliminary analysis is made which indicates that the water vapor environment lowers crack tip strains. Strain distribution within the plastic zone is shown to fit a logarithmic function, as opposed to a power function, although there is still some uncertainty in this result. Work on 7075-T6 and the powder metallurgy alloy MA-87 is continuing, with definitive results expected next year. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 18, 1981
- Accession Number
- ADA105529
Entities
People
- D. L. Davidson
- J. Lankford
Organizations
- Southwest Research Institute