- Type: This is a **cantilever beam** with end loading — classic bending problem
## Result Extraction — Confirmed (Gen 003)
| Output | Method | Expression/Sensor | Status |
|--------|--------|-------------------|--------|
| Mass | NX expression | **`p173`** (`body_property147.mass` in kg) | ✅ Confirmed — journal extracts to `_temp_mass.txt` |
| Tip displacement | OP2 parse via pyNastran | Max Tz at free end | ✅ Working — 17.93 mm at baseline-ish DVs |
| Von Mises stress | OP2 parse via pyNastran | CQUAD4 shell max VM | ✅ Working — 111.9 MPa at baseline-ish DVs |
> **Mass extraction:** Journal extracts `p173` expression after solve and writes `_temp_mass.txt`. Python reads this file. Expression `p1` from KBS session was incorrect — `p173` confirmed via binary introspection.
>
> **pyNastran note:** Warns "nx version 2512 not supported" but reads OP2 files correctly. Stress output from pyNastran is in kPa — divide by 1000 for MPa.
## Mesh Details
| Property | Value | Notes |
|----------|-------|-------|
| Element type | CQUAD4 | 4-node quadrilateral, first-order |
| Element size | 33.7 mm | 67.4 / 2 — Antoine says refinement is "not for now" |
| Mesh method | Subdivision-based | Auto-mesh with size control |
| Convergence | ❓ **NOT VERIFIED** | Gap G8 partially closed (type known), but convergence check still needed |
### Mesh Estimate
- Beam length 5,000 mm / 33.7 mm ≈ 148 elements along length
- Perimeter of I-beam cross-section ≈ varies — but total mesh likely 10K–50K elements
- Expected DOF: 60K–300K → SOL 101 solve time: seconds to low minutes
## Solver Considerations
*From Technical Breakdown (Gen 001), updated with KBS data + Gen 003 run data:*
- **Linear assumption:** With 1,133 kg beam under 98 kN load, deflections are ~18 mm at 5,000 mm span. L/δ ≈ 280 — linear assumption is reasonable.
- **Mesh sensitivity:** Stress at hole edges is mesh-dependent. CQUAD4 at 33.7 mm may not fully resolve SCF at 300 mm diameter holes (~28 elements around circumference — probably adequate but needs verification).
- **Mesh morphing vs remesh:** Parametric NX models typically remesh on update. Need to confirm behavior across DV range (Gap G7).
- **Runtime:** ✅ Confirmed **~12 seconds per evaluation** (single beam, CQUAD4 thin shell on dalidou). Very fast.
- **Unit system:** NX model uses kg-mm-s (kgf for force). Nastran output stress in kPa → divide by 1000 for MPa.
## Validation Checklist
- [x] Baseline mass matches NX expression `p173` (1,133.01 kg)
- [x] Displacement measured — 17.93 mm at baseline-ish DVs (G10 closed)
| **Previous config** | NX 2412 | ❌ Failed — "Part file is from a newer version" |
| **pyNastran compat** | Warns "nx version 2512 not supported" | ✅ But reads OP2 files correctly |
> ⚠️ **Critical lesson (2026-02-11):** Solver was originally configured for NX 2412 but model files are from DesigncenterNX 2512. NX refuses to load with "Part file is from a newer version." Must match version exactly.
### Path Resolution on Windows — Critical
**Bug discovered:** `Path.absolute()` on Windows does **NOT** resolve `..` components (unlike `Path.resolve()`).
```python
# WRONG — leaves ".." in path, NX can't find referenced parts
NX `.sim` files store **absolute internal references** to `.fem` and `.prt` files. Copying model files to iteration folders breaks these references (`Parts.Open` returns `None`).
**Solution:** Solve on master model **in-place** (in the `models/` directory) with backup/restore for isolation:
1. Backup master model files before each trial
2. Write expressions, rebuild, solve in `models/`
3. Archive outputs (OP2, F06, params, results) to iteration folder
4. Restore master from backup
See DEC-HB-008 in DECISIONS.md.
## History
- **Gen 001** (2026-02-09): Initial documentation from technical breakdown. All solver details pending gap resolution.
- **Gen 002** (2026-02-10): Confirmed from KBS session — CQUAD4 thin shell, 33.7 mm element size, cantilever BCs (left fixed, right 10,000 kgf down), mass via `p173`. Material: AISI 1005.
- **Gen 003** (2026-02-11): First real results! DesigncenterNX 2512 version confirmed, path resolution bugs fixed, backup/restore in-place solving architecture, mass extraction via journal. Displacement=17.93mm, Stress=111.9MPa, Solve time ~12s/trial.
## NX Automation Workflow
**This model uses the SIMPLE workflow** (single-part, no assembly FEM).
