forked from 1b-agent/fieldcraft-upstream
jyvikoandClaude Opus 5.5
9ba6224bb7
nl-hybrid-incompressible: 27 hybrid hex8 at ν = 0.4999 pulled to λ = 2 by a prescribed displacement, against the compressible neo-Hookean closed form (1.4·10⁻⁹); its first iterations need the LDLᵀ factorization. ROADMAP and parity updated, docs/oracle.md regenerated. Co-Authored-By: Claude Opus 5.5 <[email protected]>
Nearly incompressible hybrid block under prescribed stretch
A unit cube of 3 × 3 × 3 hybrid hex8 elements on three symmetry planes, neo-Hookean with E = 3, ν = 0.4999 (κ/μ ≈ 5000), pulled to λ = 2 by a prescribed displacement in a nonlinear static step. The first iterations of an increment strain only the elements next to the moving face, whose mixed tangents are then indefinite: the step relies on the LDLᵀ factorization (before it, every increment was cut back until the step hit its cap). The reference is the compressible decoupled energy's uniaxial stress with the lateral stretch found by bisection so σ_yy = 0.