docs: update KB and project docs with 2026-02-11 progress
- KB Gen 003: NX version (DesigncenterNX 2512), first real results - sol101-static.md: path resolution lessons, in-place solving, result extraction confirmed - CONTEXT.md: solver pipeline operational, first results (disp=17.93mm, stress=111.9MPa) - DECISIONS.md: DEC-HB-008 to DEC-HB-011 (backup/restore, iteration arch, history DB, git workflow) - optimization_engine/README.md: created (DesigncenterNX support, path resolution, NX file refs) - studies/01_doe_landscape/README.md: updated architecture, iteration folders, history DB - _index.md: closed gaps G3,G4,G6,G10-G14, updated generation to 003
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**Simulation:** Beam_sim1.sim
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**Solver:** NX Nastran SOL 101 (Linear Static)
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**Status:** Setup confirmed from KBS session (Gen 002). Baseline run needed.
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**Status:** ✅ Running — first real results obtained 2026-02-11. Automated DOE pipeline operational.
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---
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- Application: Right side (free end) of beam
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- Type: This is a **cantilever beam** with end loading — classic bending problem
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## Result Extraction
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## Result Extraction — Confirmed (Gen 003)
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| Output | Method | Expression/Sensor | Status |
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|--------|--------|-------------------|--------|
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| Mass | NX expression | **`p1`** (NOT `p173`) | ✅ Confirmed — 11.33 kg baseline |
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| Tip displacement | ❓ Sensor or .f06 parse | TBD | Gap G3, G6 — need baseline run |
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| Von Mises stress | ❓ Sensor or .f06 parse | TBD | Gap G4, G6 — need baseline run |
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| Mass | NX expression | **`p173`** (`body_property147.mass` in kg) | ✅ Confirmed — journal extracts to `_temp_mass.txt` |
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| Tip displacement | OP2 parse via pyNastran | Max Tz at free end | ✅ Working — 17.93 mm at baseline-ish DVs |
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| Von Mises stress | OP2 parse via pyNastran | CQUAD4 shell max VM | ✅ Working — 111.9 MPa at baseline-ish DVs |
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> ⚠️ **Mass expression changed:** `p1` confirmed in KBS session, replacing previous assumption of `p173`. Extractor config must be updated.
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> **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.
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>
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> **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.
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## Mesh Details
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## Solver Considerations
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*From Technical Breakdown (Gen 001), updated with KBS data:*
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*From Technical Breakdown (Gen 001), updated with KBS data + Gen 003 run data:*
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- **Linear assumption:** With 11.33 kg beam under 98 kN load, deflections may be significant relative to beam dimensions. L/δ ratio needs verification from baseline run.
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- **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.
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- **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).
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- **Mesh morphing vs remesh:** Parametric NX models typically remesh on update. Need to confirm behavior across DV range (Gap G7).
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- **Runtime estimate:** Single beam, CQUAD4 thin shell → likely **seconds per evaluation**. Very fast.
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- **Runtime:** ✅ Confirmed **~12 seconds per evaluation** (single beam, CQUAD4 thin shell on dalidou). Very fast.
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- **Unit system:** NX model uses kg-mm-s (kgf for force). Nastran output stress in kPa → divide by 1000 for MPa.
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## Validation Checklist
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- [ ] Baseline mass matches NX expression `p1` (11.33 kg)
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- [ ] Baseline displacement measured (was 22 mm at old model state — **needs re-verification** G10)
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- [ ] Baseline stress measured (never had a value — **G11**)
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- [x] Baseline mass matches NX expression `p173` (1,133.01 kg)
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- [x] Displacement measured — 17.93 mm at baseline-ish DVs (G10 closed)
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- [x] Stress measured — 111.9 MPa at baseline-ish DVs (G11 closed)
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- [ ] Mesh convergence verified at baseline
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- [ ] Mesh quality acceptable at DV range extremes
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- [ ] Model rebuilds cleanly at all 4 corners of design space (Gap G7)
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- [ ] Stress at hole edges resolved with current mesh density
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## NX Version & Environment — Confirmed (Gen 003)
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| Item | Value | Notes |
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|------|-------|-------|
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| **NX Version** | **DesigncenterNX 2512** | Siemens rebranded NX to "DesigncenterNX" |
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| **Install path** | `C:\Program Files\Siemens\DesigncenterNX2512` | On dalidou (Windows solver node) |
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| **Previous config** | NX 2412 | ❌ Failed — "Part file is from a newer version" |
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| **pyNastran compat** | Warns "nx version 2512 not supported" | ✅ But reads OP2 files correctly |
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> ⚠️ **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.
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### Path Resolution on Windows — Critical
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**Bug discovered:** `Path.absolute()` on Windows does **NOT** resolve `..` components (unlike `Path.resolve()`).
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```python
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# WRONG — leaves ".." in path, NX can't find referenced parts
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path = Path("../../models/Beam_sim1.sim").absolute()
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# → C:\Users\antoi\Atomizer\projects\hydrotech-beam\studies\01_doe_landscape\..\..\models\Beam_sim1.sim
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# CORRECT — fully resolves path
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path = Path("../../models/Beam_sim1.sim").resolve()
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# → C:\Users\antoi\Atomizer\projects\hydrotech-beam\models\Beam_sim1.sim
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```
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**Rule:** Use `.resolve()` everywhere when constructing paths for NX. NX cannot follow `..` references in paths.
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### NX File References — In-Place Solving Required
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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`).
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**Solution:** Solve on master model **in-place** (in the `models/` directory) with backup/restore for isolation:
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1. Backup master model files before each trial
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2. Write expressions, rebuild, solve in `models/`
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3. Archive outputs (OP2, F06, params, results) to iteration folder
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4. Restore master from backup
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See DEC-HB-008 in DECISIONS.md.
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## History
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- **Gen 001** (2026-02-09): Initial documentation from technical breakdown. All solver details pending gap resolution.
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- **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 `p1`. Material: AISI 1005.
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- **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.
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- **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.
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## NX Automation Workflow
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