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 <noreply@anthropic.com>
9 lines
635 B
Markdown
9 lines
635 B
Markdown
# Nearly incompressible hybrid block under prescribed stretch
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A unit cube of 3 × 3 × 3 hybrid hex8 elements on three symmetry planes, neo-Hookean with E = 3,
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ν = 0.4999 (κ/μ ≈ 5000), pulled to λ = 2 by a prescribed displacement in a nonlinear static
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step. The first iterations of an increment strain only the elements next to the moving face,
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whose mixed tangents are then indefinite: the step relies on the LDLᵀ factorization (before it,
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every increment was cut back until the step hit its cap). The reference is the compressible
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decoupled energy's uniaxial stress with the lateral stretch found by bisection so σ_yy = 0.
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