NINI
56 lines
1.6 KiB
Markdown
56 lines
1.6 KiB
Markdown
# Sprint Contract: MITC4 Geometry Directors
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## Objective
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Implement or rebuild MITC4 shape functions, natural-coordinate node order, element-center director policy, local director axes, and integration-point local bases.
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## Required Reading
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- /AGENTS.md
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- /docs/MITC4_FORMULATION.md
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- /docs/NUMERICAL_CONVENTIONS.md
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- /docs/ADR.md
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## Scope
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- Define `N1..N4` and derivatives for FESA natural coordinates.
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- Define tying points `A`, `B`, `C`, and `D`.
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- Build element-center director `Vn` from midsurface geometry.
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- Build nodal `V1`, `V2`, `Vn` and integration local Cartesian basis.
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- Add invalid/singular element diagnostics for near-zero normal, basis, Jacobian, and thickness.
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## Allowed Files
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- `include/`
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- `src/`
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- `tests/`
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- `PLAN.md`
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- `PROGRESS.md`
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## Explicit Non-Goals
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- Do not compute stiffness.
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- Do not add Abaqus `*Orientation` or nodal normal parsing.
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- Do not add mesh quality diagnostics.
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## Tests To Write First
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- Shape function partition-of-unity and derivative tests.
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- Node order and tying-point coordinate tests.
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- Flat element normal and right-handed basis tests.
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- Fallback axis tests when `EY x Vn` is near zero.
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- Invalid geometry diagnostic tests.
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## Reference Artifacts
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- None.
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## Acceptance Commands
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```bash
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python scripts/validate_workspace.py
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```
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## Evaluator Checklist
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- Geometry matches `docs/MITC4_FORMULATION.md`.
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- The old averaged-edge basis is not used as the binding formulation.
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- No stress/strain or stiffness logic is slipped into this step.
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## Handoff Requirements
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- Record MITC4 geometry readiness in `PROGRESS.md`.
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## Do Not
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- Do not silently support strongly warped/nodal-director behavior beyond the documented Phase 1 policy.
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