{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"f7aedd5fc68d67e6309fa2df4ed1a5d4c6cd75fa6e376c64462aacbb5a163869","created":"2026-10-03T07:17:59Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"dfed97b911905feb1397b4785b8d41703144e0501eba92dfb8184d8732f8be41","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"cm.crystal-plasticity.psb-crack-initiation","kind":"phenomenon","literature_status":"open","n":"1","parents":[],"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.","posed_since":"","precise":"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.","problem_ref":null,"references":"","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.","status_note":"","title":"How persistent slip bands initiate fatigue cracks","topic_ref":"01aa4fb74d0c96c5784d789590ab08ed4af0e1bc9234f0d6784e666e779187ae"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"2818c1c6781ac5fd849bf3d8394c34c851fd90dc2dedfe5f3cc3f7e1838f36f7","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"234d2df80bf11e52e43de943d205e176c0888dadd049ba56fd2a02133a850320","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"qYsAcyBc2wsavSTrpAYFISjqyHYUbaJP_LJUP3O_XbOno6R0qcfy-btAXzR5FcPkBABRKI8IWZbBKWBJzbqQDg"},"schema":"pubphys.envelope/1"},"record_hash":"2818c1c6781ac5fd849bf3d8394c34c851fd90dc2dedfe5f3cc3f7e1838f36f7","leaf_index":926}