forked from 1b-agent/fieldcraft-upstream
jyvikoandClaude Opus 5.5
8ca2dddeec
Theory cases for the nonlinear solver, each frozen as a fixture: uniaxial stretch of a neo-Hookean block to twice its length (closed form), the nonlinear patch test on a distorted hex8 mesh, a quarter turn of the same mesh (objectivity: zero stress), the elastica of a hex20 cantilever at P L²/(E I) = 1, 2, 5, 10 against Bisshopp–Drucker (0.2–0.5 %), and the inflation of a thick neo-Hookean tube by a follower pressure against Rivlin's closed form (0.08 % at the bore). A finite-strain Cook's membrane is pending its transcribed reference. docs/fem.md describes the formulation, the material point interface, the follower-pressure choice and what nonlinear steps refuse; the literature, parity and roadmap pages follow. Co-Authored-By: Claude Opus 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm
Inflation of a thick neo-Hookean cylinder (follower pressure)
A quarter of a tube A = 10, B = 20, one unit long, in plane strain (symmetry planes x = 0, y = 0 and both ends), 6 × 16 hybrid hex20 elements, neo-Hookean with E = 3, ν = 0.4995 (μ = 1.00033, κ = 1000). The bore pressure p = 0.428371199 follows the deforming bore; the incompressible closed form puts the bore at a = 15 and the outer wall at b = 22.912878475. This is the follower-pressure case: the pressure turns with the bore and grows with its area.