{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"34c838cbbd10374ac21b922a0693373646246f95107da02030ca7ab18147c932","created":"2026-10-03T07:17:59Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"3a6a629c01a19d1f538368b5c15c30047c3e8d57ab1d4ca9bc7a023d90a20c9a","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"cm.crystal-plasticity.micropillar-size-effect","kind":"phenomenon","literature_status":"partially-resolved","n":"1","parents":[],"plain":"Metal pillars a few hundredths of a millimeter wide or smaller are many times stronger than large crystals, with strength rising as the diameter shrinks by a power law. Several mechanisms are proposed, but none predicts the exponent and its variation between metals.","posed_since":"2004","precise":"Flow stress of FCC micropillars scales as $\\tau \\sim D^{-n}$ with $n \\sim 0.6 \\text{ to } 0.7$ for diameters D from about $1e-5 \\text{ to } 1e-3\\,\\mathrm{cm}$ (Uchic et al. 2004), while BCC metals show smaller n correlated with the temperature dependence of screw dislocation mobility. Determine which mechanism (truncation of single-arm sources, dislocation starvation, exhaustion hardening) controls n, and whether n is universal for FCC, via 3D dislocation dynamics compared with experimental statistics. An answer is the mechanism with predicted n versus material, D and initial dislocation density.","problem_ref":null,"references":"","settled_by":"Dislocation dynamics simulations with measured initial microstructures reproducing n for FCC and BCC pillars, tested on pillars of controlled initial dislocation density.","status_note":"Source-truncation models reproduce $n \\sim 0.6$ for FCC; the BCC trend and the role of initial dislocation density remain unresolved.","title":"Origin of the size dependence of micropillar strength","topic_ref":"01aa4fb74d0c96c5784d789590ab08ed4af0e1bc9234f0d6784e666e779187ae"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"f0a3391ddf8d6b7ac8867d34f4e8345dcfe09664b7883c94e22bf2c21c1bfb9b","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"a9dee32b3970b780c501498a718f588e4d7d4659667e5a0e5c41dc38835c2f7e","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"HX0bs9Re1rQdAaQ2wYJ3tUecO17fplqmXHoAaUlqyowwG1kgyzQojmRCW6VJQPuDUitkWuyhisFgVfkPpNY9Cg"},"schema":"pubphys.envelope/1"},"record_hash":"f0a3391ddf8d6b7ac8867d34f4e8345dcfe09664b7883c94e22bf2c21c1bfb9b","leaf_index":925}