How persistent slip bands initiate fatigue cracks · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
How persistent slip bands initiate fatigue cracks
Plain
Under repeated small loads, metals form thin bands of concentrated slip with a ladder-like dislocation structure, and cracks begin where these bands meet the surface. How the bands push out surface ridges and start cracks has not been derived from dislocation physics.
Precise · changed · core
Revision 1: In cyclically loaded Cu single crystals, persistent slip bands with dislocation ladder walls spaced about 1e-4 cm carry localized plastic strain and produce surface extrusions and intrusions where cracks nucleate. Determine the mechanism producing extrusions (vacancy generation by annihilation of edge dislocation dipoles, as in the Essmann-Gosele-Mughrabi model, or irreversible slip) and predict the number of cycles to crack initiation versus plastic strain amplitude. An answer is a model validated against measured extrusion growth rates and initiation lives.
Revision 2: In cyclically loaded Cu single crystals, persistent slip bands with dislocation ladder walls spaced about $10^{-4}$ cm carry localized plastic strain and produce surface extrusions and intrusions where cracks nucleate. Determine the mechanism producing extrusions (vacancy generation by annihilation of edge dislocation dipoles, as in the Essmann-Gosele-Mughrabi model, or irreversible slip) and predict the number of cycles to crack initiation versus plastic strain amplitude. An answer is a model validated against measured extrusion growth rates and initiation lives.
Settled by
In situ measurement of extrusion growth and point-defect content in persistent slip bands, compared with a dislocation-based model predicting initiation life.
Kind
phenomenon
Answer type
mechanism
References
(empty)
Literature status
open
Status note
(empty)
Posed since
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Decisions