NINI
72 lines
2.6 KiB
Markdown
72 lines
2.6 KiB
Markdown
# Step 11: mitc4-element-baseline
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## Sprint Contract
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### Objective
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Implement the baseline MITC4 element utilities and stiffness path after the formulation gate is closed.
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### Required Reading
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- /AGENTS.md
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- /PROGRESS.md
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- /PLAN.md
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- /docs/README.md
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- /docs/HARNESS_ENGINEERING.md
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- /docs/PRD.md
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- /docs/ARCHITECTURE.md
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- /docs/ADR.md
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- /docs/NUMERICAL_CONVENTIONS.md
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- /docs/MITC4_FORMULATION.md
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- /phases/1-linear-static-mitc4/step10.md
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### Scope
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- Implement shape functions, derivatives, local basis utilities, MITC shear tying per the finalized formulation, stiffness calculation, and drilling stiffness parameter path.
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- Keep the element behind runtime-polymorphic element interfaces.
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- Produce a 24x24 element stiffness for four-node shell elements with six DOFs per node.
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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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- `docs/MITC4_FORMULATION.md` only for errata discovered during implementation
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- `PLAN.md`
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- `PROGRESS.md`
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- `phases/1-linear-static-mitc4/index.json`
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### Explicit Non-Goals
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- Do not implement S4R, reduced integration, hourglass control, nonlinear kinematics, pressure loads, composites, thermal coupling, or mesh quality checks.
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- Do not implement formulas that are still placeholders in `docs/MITC4_FORMULATION.md`.
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- Do not optimize element kernels before baseline benchmark behavior is established.
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### Tests To Write First
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- Shape function partition and nodal interpolation tests.
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- Derivative and Jacobian/local basis tests.
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- 24x24 dimension and symmetry tests.
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- Rigid body or patch-style checks appropriate to the documented formulation.
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- Drilling stiffness sensitivity tests.
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### Reference Artifacts
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- None required for this unit-level step. Stored-reference regression is Step 14.
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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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- Step 10 formulation decisions are closed before code is added.
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- Element interface uses runtime polymorphism as documented.
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- Stiffness output dimension, DOF order, symmetry, and drilling behavior are tested.
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- No S4R or nonlinear behavior was introduced.
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### Handoff Requirements
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- Record implemented formulation surface and validation in `PROGRESS.md`.
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- Update `PLAN.md` if benchmark or formulation risks remain.
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- Update the matching phase index entry: use `completed` with a one-line `summary`, or `blocked` with `blocked_reason`, or `error` with `error_message`.
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## Verification
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1. Run the acceptance command.
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2. Inspect tests against the finalized MITC4 formulation checklist.
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## Do Not
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- Do not hide formulation uncertainty in comments or TODOs inside executable code.
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