FESADev/phases/euler-beam-3d/step1.md

Step 1: research-evidence

Read These Files First

Read the following files before editing:

• /AGENTS.md
• /docs/PRD.md
• /docs/ARCHITECTURE.md
• /docs/ADR.md
• /docs/requirements/euler-beam-3d.md
• /docs/research/README.md

Task

Create /docs/research/euler-beam-3d-research.md.

Summarize the evidence needed to implement the approved kernel-first 3D Euler-Bernoulli beam increment. The document must be implementation-oriented and must include:

• supported theory: straight prismatic Euler-Bernoulli beam, axial, torsion, and two uncoupled bending planes
• assumptions and applicability limits
• local DOF ordering and sign convention used by the planned matrix
• source reliability classification
• benchmark-style checks that do not require external reference solver execution:
  • local stiffness symmetry
  • axial-only response
  • torsion-only response
  • bending about local y
  • bending about local z
  • rigid body translation/rotation zero internal forces in local coordinates
  • global transform identity for an axis-aligned beam
• risks: orientation vector parallel to element axis, near-zero length, nonpositive section constants, ill-conditioning for very slender elements

If internet access or a FEM wiki is used, cite sources briefly. Do not include long copyrighted excerpts.

Do not create C++ files in this step.

Tests To Write First

• No C++ test is required in this documentation-only step.

Acceptance Criteria

python -m unittest discover -s scripts -p "test_*.py"
python scripts/validate_workspace.py

Verification Notes

1. Confirm the research document ties each source or theory point to a planned implementation check.
2. Confirm unresolved items are listed as risks or open issues instead of silently assumed.
3. Update phases/euler-beam-3d/index.json step 1:
   • success: "status": "completed", "summary": "3D Euler beam research evidence added"
   • failure after retries: "status": "error", "error_message": "<specific error>"
   • blocked: "status": "blocked", "blocked_reason": "<specific reason>"

Forbidden

• Do not modify source, test, reference, or I/O contract files.