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feat: Add E11 Part Mass extractor, document pyNastran mass accuracy issue

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New E11 Part Mass Extractor:
- Add nx_journals/extract_part_mass_material.py - NX journal using
  NXOpen.MeasureManager.NewMassProperties() for accurate geometry-based mass
- Add optimization_engine/extractors/extract_part_mass_material.py - Python
  wrapper that reads JSON output from journal
- Add E11 entry to extractors/catalog.json

Documentation Updates:
- SYS_12_EXTRACTOR_LIBRARY.md: Add mass accuracy warning noting pyNastran
  get_mass_breakdown() under-reports ~7% on hex-dominant meshes with
  tet/pyramid fill elements. E11 (geometry .prt) should be preferred over
  E4 (BDF) unless material is overridden at FEM level.
- 01_CHEATSHEET.md: Add mass extraction tip

V14 Config:
- Expand design variable bounds (blank_backface_angle max 4.5°,
  whiffle_triangle_closeness max 80mm, whiffle_min max 60mm)

Testing showed:
- E11 from .prt: 97.66 kg (accurate - matches NX GUI)
- E4 pyNastran get_mass_breakdown(): 90.73 kg (~7% under-reported)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Antoine
2025-12-11 22:15:36 -05:00
parent c1f2634636
commit 70ac34e3d3
6 changed files with 636 additions and 3 deletions
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12
docs/protocols/system/SYS_12_EXTRACTOR_LIBRARY.md
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@@ -195,6 +195,18 @@ material = extractor.material_name
- `NXOpen.Body.GetBodies()`
- `NXOpen.PhysicalMaterial`
**IMPORTANT - Mass Accuracy Note**:
> **Always prefer E11 (geometry-based) over E4 (BDF-based) for mass extraction.**
>
> Testing on hex-dominant meshes with tet/pyramid fill elements revealed that:
> - **E11 from .prt**: 97.66 kg (accurate - matches NX GUI)
> - **E4 pyNastran get_mass_breakdown()**: 90.73 kg (~7% under-reported)
> - **E4 pyNastran sum(elem.Volume())*rho**: 100.16 kg (~2.5% over-reported)
>
> The `get_mass_breakdown()` function in pyNastran has known issues with mixed-element
> meshes (CHEXA + CPENTA + CPYRAM + CTETRA). Use E11 with the NX journal for reliable
> mass values. Only use E4 if material properties are overridden at FEM level.
### E6: Field Data Extraction
**Module**: `optimization_engine.extractors.field_data_extractor`