116 lines
4.2 KiB
Markdown
116 lines
4.2 KiB
Markdown
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# Optimization Engine
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Core optimization engine for Atomizer structural optimization projects.
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## Overview
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The optimization engine provides NX Nastran integration, result extraction, and optimization orchestration. Originally developed for the SAT3 mirror project, now generalized for multiple projects including Hydrotech Beam.
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## NX Integration (`nx/`)
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### Supported NX Versions
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| Version | Status | Notes |
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|---------|--------|-------|
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| NX 2412 | ⚠️ Legacy | Original development version |
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| **DesigncenterNX 2512** | ✅ Current | Siemens rebranded NX to "DesigncenterNX". Install path: `C:\Program Files\Siemens\DesigncenterNX2512` |
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> **Important:** Siemens rebranded NX to "DesigncenterNX" starting with version 2512. The install directory, executable paths, and search paths all use the new name. Solver configuration must specify `2512` and include `DesigncenterNX` in search paths.
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### Key Files
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| File | Purpose |
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|------|---------|
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| `solver.py` | NX solver interface — manages NX session, expression updates, solve execution |
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| `solve_simulation.py` | NX journal script — runs inside NXOpen Python, handles simple + assembly workflows |
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| `solve_simulation_simple.py` | Simplified journal for single-part (simple) workflow |
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| `updater.py` | Expression updater — writes `.exp` files, handles unit types |
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| `export_expressions.py` | Export expressions from NX model |
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| `import_expressions.py` | Import expressions into NX model |
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| `session_manager.py` | NX session lifecycle management |
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| `model_cleanup.py` | Model cleanup utilities |
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| `mesh_converter.py` | Mesh format conversion |
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### Path Resolution — CRITICAL on Windows
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**`Path.absolute()` on Windows does NOT resolve `..` components.** Use `Path.resolve()` everywhere.
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```python
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# WRONG — NX cannot follow ".." in paths
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path = Path("../../models/Beam_sim1.sim").absolute()
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# → C:\...\studies\01_doe_landscape\..\..\models\Beam_sim1.sim ← BROKEN
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# CORRECT — fully resolved path
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path = Path("../../models/Beam_sim1.sim").resolve()
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# → C:\...\projects\hydrotech-beam\models\Beam_sim1.sim ← WORKS
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```
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This applies to ALL paths passed to NX journals, including:
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- `.sim` file path
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- `.exp` file path
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- Model directory path
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- Output file 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 different directories breaks these references (`Parts.Open` returns `None`).
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**Solution:** Always solve on master model files in-place. Use backup/restore for isolation between optimization trials:
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1. Backup master model files before trial
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2. Write expressions, rebuild, solve in original location
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3. Archive outputs (OP2, F06) to trial-specific folder
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4. Restore master from backup
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### Expression Units
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When writing `.exp` files for NX:
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- Length design variables: unit = `MilliMeter`
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- Integer expressions (e.g., `hole_count`): unit = `Constant`
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- **Critical:** Using wrong unit silently corrupts the model
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### Workflow Types
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**Simple workflow** (single-part, e.g., Hydrotech Beam):
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```
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Beam.prt → Beam_fem1_i.prt → Beam_fem1.fem → Beam_sim1.sim
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```
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**Assembly FEM workflow** (multi-part, e.g., SAT3 mirror):
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```
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Multiple .prt → .afm → .sim (node merge, label conflicts)
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```
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The journal auto-detects workflow type by checking for `.afm` files.
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## Result Extraction
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### pyNastran Compatibility
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pyNastran warns "nx version 2512 not supported" but **reads OP2 files correctly**. Safe to ignore the warning.
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**Unit note:** pyNastran returns stress in kPa for NX models using kg-mm-s unit system. Divide by 1000 for MPa.
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### Mass Extraction
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Mass is extracted via NX expression `p173` (or project-specific expression). The journal writes the value to a temp file (`_temp_mass.txt`) after solve, which Python reads.
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## Dependencies
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- Python 3.10+
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- pyNastran (OP2 parsing)
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- NXOpen Python API (on Windows solver node)
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- Optuna (optimization orchestration)
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- scipy, numpy, pandas
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## Projects Using This Engine
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| Project | Status | NX Version | Workflow |
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|---------|--------|------------|----------|
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| Hydrotech Beam | Active (DOE Phase 1) | DesigncenterNX 2512 | Simple |
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| SAT3 Mirror | Legacy reference | NX 2412 | Assembly FEM |
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---
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*Last updated: 2026-02-11*
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