{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"b7b249076794d84ed86fbd428f227ed34504661fe7f1725b1e9b9396c59edc4d","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b","f0a3391ddf8d6b7ac8867d34f4e8345dcfe09664b7883c94e22bf2c21c1bfb9b"],"salt":"8dc092023692d3c9272be3ae8021418d27302c5d7a8f053ee5cec357cb70b1d6","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":"2","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 $10^{-5} \\text{ to } 10^{-3}\\,\\mathrm{cm}$ (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":"f0a3391ddf8d6b7ac8867d34f4e8345dcfe09664b7883c94e22bf2c21c1bfb9b","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":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"c552034ed0a051ae71cfcab425dd7b9314989677fc081bf4b86997adbbce07cc","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"81c816097babba21eee89bba027c8bca1bbad211bbe65c04840b80dee45a693d","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"E-MFFyTwHnzkRwVY1zZhBGNIeub5TfLdMuDMYE_vJn3XNJc5sVo76_dBE5lpohiwUNtP30l5ZzJcaHIBOUF2AQ"},"schema":"pubphys.envelope/1"},"record_hash":"c552034ed0a051ae71cfcab425dd7b9314989677fc081bf4b86997adbbce07cc","leaf_index":2716}