solver: nonlinear static analysis by Newton–Raphson with automatic increments

solve.nonlinear follows a nonlinear static step in load increments: dead
loads and prescribed displacements ramp with the load factor, a pressure
follows the deformed faces (its load stiffness symmetrised so the
supernodal Cholesky stays), the consistent tangent is refactored every
iteration with an optional line search, and an increment converges on
force, displacement and energy together. Increments start from the
extrapolated last one, grow after fast convergence and are cut back on
inversion, a non-finite or growing residual, an indefinite tangent or too
many iterations; the step stops cleanly at the minimum increment, the
increment cap or the Newton iteration limit. Elements are assembled in
parallel in label order (same bits on any thread count). Results carry
Cauchy stress, logarithmic strain, the increment history and a displacement
frame per increment, which results.frame and the results panel show.
Trusses, shells, beams, plane stress, incompatible modes, temperature and
centrifugal loads are refused by name; couplings warn that they stay
linear.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

docs/features.md

@@ -56,7 +56,7 @@ the control channel and AI agents over MCP (docs/mcp.md) run the same commands.
 
 | Panel | Capability | Status | Command |
 |---|---|---|---|
-| Materials | Material — Elastic (isotropic, orthotropic) material with density | ready | `model.material.create`, `model.material.edit`, `model.material.delete` |
+| Materials | Material — Elastic (isotropic, orthotropic) material with density; neo-Hookean hyperelasticity for nonlinear steps | ready | `model.material.create`, `model.material.edit`, `model.material.delete` |
 | Materials | Plasticity — Von Mises plasticity: bilinear, hardening table or Johnson–Cook | ready | `model.material.plasticity` |
 | Materials | Hyperelastic — Hyperelastic material models | coming soon (M8) |  |
 | Materials | Damage — Johnson–Cook damage and element erosion | ready | `model.material.damage` |
@@ -78,7 +78,7 @@ the control channel and AI agents over MCP (docs/mcp.md) run the same commands.
 
 | Panel | Capability | Status | Command |
 |---|---|---|---|
-| Steps | Step — A linear static or frequency step with its output | ready | `model.step.create`, `model.step.edit`, `model.step.delete` |
+| Steps | Step — A linear or nonlinear static, frequency, heat or explicit step with its output | ready | `model.step.create`, `model.step.edit`, `model.step.delete` |
 | Steps | Activate — Choose which loads and boundary conditions act in a step | ready | `model.step.activate` |
 | Steps | Step Table — The step by load and boundary condition table | ready | `model.activity` |
 | Procedures | Amplitude — Time and frequency amplitudes | coming soon (M7) |  |
@@ -122,7 +122,7 @@ the control channel and AI agents over MCP (docs/mcp.md) run the same commands.
 | Decks | Nastran Deck — Write Nastran bulk data (SOL 101, 103) | ready | `deck.write {"format":"nastran"}` |
 | Decks | LS-DYNA Deck — Write an LS-DYNA keyword file | ready | `deck.write {"format":"lsdyna"}` |
 | Decks | Read Deck — Read a deck, keeping keywords FieldCraft does not know | coming soon (M9) |  |
-| Implicit | Static — Linear static (or coupled temperature–displacement) solve of a step with FieldCraft's own solver; heat transfer in the drop-down | ready | `solve.static`, `solve.heat` |
+| Implicit | Static — Linear static (or coupled temperature–displacement) solve of a step with FieldCraft's own solver; nonlinear static and heat transfer in the drop-down | ready | `solve.static`, `solve.nonlinear`, `solve.heat` |
 | Implicit | Frequency — Natural frequencies and mode shapes of a frequency step | ready | `solve.frequency` |
 | Explicit | Explicit — Transient dynamics of an explicit step by central differences (contact and erosion coming in M10) | ready | `solve.explicit` |
 | Explicit | Blast & Impact — EOS-driven fluids with fluid–structure contact (ALE or SPH) | coming soon (M14) |  |