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feat(hydrotech-beam): Phase 1 LHS DoE study code

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Implements the optimization study code for Phase 1 (LHS DoE) of the
Hydrotech Beam structural optimization.

Files added:
- run_doe.py: Main entry point — Optuna study with SQLite persistence,
  Deb's feasibility rules, CSV/JSON export, Phase 1→2 gate check
- sampling.py: 50-point LHS via scipy.stats.qmc with stratified integer
  sampling ensuring all 11 hole_count levels (5-15) are covered
- geometric_checks.py: Pre-flight feasibility filter — hole overlap
  (corrected formula: span/(n-1) - d ≥ 30mm) and web clearance checks
- nx_interface.py: NX automation module with stub solver for development
  and NXOpen template for Windows/dalidou integration
- requirements.txt: optuna, scipy, numpy, pandas

Key design decisions:
- Baseline enqueued as Trial 0 (LAC lesson)
- All 4 DV expression names from binary introspection (exact spelling)
- Pre-flight geometric filter saves compute and prevents NX crashes
- No surrogates (LAC lesson: direct FEA via TPE beats surrogate+L-BFGS)
- SQLite persistence enables resume after interruption

Tested end-to-end with stub solver: 51 trials, 12 geometric rejects,
39 solved, correct CSV/JSON output.

Ref: OPTIMIZATION_STRATEGY.md, auditor review 2026-02-10
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2026-02-10 22:15:06 +00:00
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"""NX automation interface for Hydrotech Beam optimization.
Stub/template module for NXOpen Python API integration. The actual NX
automation runs on Windows (dalidou node) via Syncthing-synced model files.
This module defines the interface contract. The NXOpen-specific implementation
will be filled in when running on the Windows side.
NX Expression Names (confirmed via binary introspection — CONTEXT.md):
Design Variables:
- beam_half_core_thickness (mm, continuous)
- beam_face_thickness (mm, continuous)
- holes_diameter (mm, continuous)
- hole_count (integer, links to Pattern_p7)
Outputs:
- p173 (mass in kg, body_property147.mass)
Fixed:
- beam_lenght (⚠️ TYPO in NX — no 'h', 5000 mm)
- beam_half_height (250 mm)
- beam_half_width (150 mm)
References:
CONTEXT.md — Full expression map
OPTIMIZATION_STRATEGY.md §8.2 — Extractor requirements
"""
from __future__ import annotations
import logging
from dataclasses import dataclass
from typing import Protocol
logger = logging.getLogger(__name__)
# ---------------------------------------------------------------------------
# Data types
# ---------------------------------------------------------------------------
@dataclass(frozen=True)
class TrialInput:
"""Design variable values for a single trial."""
beam_half_core_thickness: float # mm — DV1
beam_face_thickness: float # mm — DV2
holes_diameter: float # mm — DV3
hole_count: int # — DV4
@dataclass
class TrialResult:
"""Results extracted from NX after a trial solve.
All values populated after a successful SOL 101 solve.
On failure, success=False and error_message explains the failure.
"""
success: bool
mass: float = float("nan") # kg — from expression `p173`
tip_displacement: float = float("nan") # mm — from SOL 101 results
max_von_mises: float = float("nan") # MPa — from SOL 101 results
error_message: str = ""
# ---------------------------------------------------------------------------
# NX expression name constants
# ---------------------------------------------------------------------------
# ⚠️ These are EXACT NX expression names from binary introspection.
# Do NOT change spelling — `beam_lenght` has a typo (no 'h') in NX.
EXPR_HALF_CORE_THICKNESS = "beam_half_core_thickness"
EXPR_FACE_THICKNESS = "beam_face_thickness"
EXPR_HOLES_DIAMETER = "holes_diameter"
EXPR_HOLE_COUNT = "hole_count"
EXPR_MASS = "p173" # body_property147.mass, kg
EXPR_BEAM_LENGTH = "beam_lenght" # ⚠️ TYPO IN NX — intentional
# ---------------------------------------------------------------------------
# Interface protocol
# ---------------------------------------------------------------------------
class NXSolverInterface(Protocol):
"""Protocol for NX solver backends.
Implementors must provide the full pipeline:
1. Update expressions → 2. Rebuild model → 3. Solve SOL 101 → 4. Extract results
"""
def evaluate(self, trial_input: TrialInput) -> TrialResult:
"""Run a full NX evaluation cycle for one trial.
Args:
trial_input: Design variable values.
Returns:
TrialResult with extracted outputs or failure info.
"""
...
def close(self) -> None:
"""Clean up NX session resources.
⚠️ LAC CRITICAL: NEVER kill NX processes directly.
Use NXSessionManager.close_nx_if_allowed() only.
"""
...
# ---------------------------------------------------------------------------
# Stub implementation (for development/testing without NX)
# ---------------------------------------------------------------------------
class NXStubSolver:
"""Stub NX solver for development and testing.
Returns synthetic results based on simple analytical approximations
of the beam behavior. NOT physically accurate — use only for
testing the optimization pipeline.
The stub uses rough scaling relationships:
- Mass ∝ (core + face) and inversely with hole area
- Displacement ∝ 1/I where I depends on core and face thickness
- Stress ∝ M*y/I (bending stress approximation)
"""
def __init__(self) -> None:
"""Initialize stub solver."""
logger.warning(
"Using NX STUB solver — results are synthetic approximations. "
"Replace with NXOpenSolver for real evaluations."
)
def evaluate(self, trial_input: TrialInput) -> TrialResult:
"""Return synthetic results based on simplified beam mechanics.
Args:
trial_input: Design variable values.
Returns:
TrialResult with approximate values.
"""
try:
return self._compute_approximate(trial_input)
except Exception as e:
logger.error("Stub evaluation failed: %s", e)
return TrialResult(
success=False,
error_message=f"Stub evaluation error: {e}",
)
def _compute_approximate(self, inp: TrialInput) -> TrialResult:
"""Simple analytical approximation of beam response.
This is a ROUGH approximation for pipeline testing only.
Real physics requires NX Nastran SOL 101.
"""
import math
# Geometry
L = 5000.0 # mm — beam length
b = 300.0 # mm — beam width (2 × beam_half_width)
h_core = inp.beam_half_core_thickness # mm — half core
t_face = inp.beam_face_thickness # mm — face thickness
d_hole = inp.holes_diameter # mm
n_holes = inp.hole_count
# Total height and section properties (simplified I-beam)
h_total = 500.0 # mm — 2 × beam_half_height (fixed)
# Approximate second moment of area (sandwich beam)
# I ≈ b*h_total^3/12 - b*(h_total-2*t_face)^3/12 + web contribution
h_inner = h_total - 2.0 * t_face
I_section = (b * h_total**3 / 12.0) - (b * max(h_inner, 0.0) ** 3 / 12.0)
# Add core contribution
I_section += 2.0 * h_core * h_total**2 / 4.0 # approximate
# Hole area reduction (mass)
hole_area = n_holes * math.pi * (d_hole / 2.0) ** 2 # mm²
# Approximate mass (steel: 7.3 g/cm³ = 7.3e-6 kg/mm³)
rho = 7.3e-6 # kg/mm³
# Gross cross-section area (very simplified)
A_gross = 2.0 * b * t_face + 2.0 * h_core * h_total
# Remove holes from web
web_thickness = 2.0 * h_core # approximate web thickness
A_holes = n_holes * math.pi * (d_hole / 2.0) ** 2
V_solid = A_gross * L
V_holes = A_holes * web_thickness
mass = rho * (V_solid - min(V_holes, V_solid * 0.8))
# Approximate tip displacement (cantilever, point load)
# δ = PL³/(3EI)
P = 10000.0 * 9.81 # 10,000 kgf → N
E = 200000.0 # MPa (steel)
if I_section > 0:
displacement = P * L**3 / (3.0 * E * I_section)
else:
displacement = 9999.0
# Approximate max bending stress
# σ = M*y/I where M = P*L, y = h_total/2
M_max = P * L # N·mm
y_max = h_total / 2.0
if I_section > 0:
stress = M_max * y_max / I_section # MPa
else:
stress = 9999.0
return TrialResult(
success=True,
mass=mass,
tip_displacement=displacement,
max_von_mises=stress,
)
def close(self) -> None:
"""No-op for stub solver."""
logger.info("Stub solver closed.")
# ---------------------------------------------------------------------------
# NXOpen implementation template (to be completed on Windows/dalidou)
# ---------------------------------------------------------------------------
class NXOpenSolver:
"""Real NXOpen-based solver — TEMPLATE, not yet functional.
This class provides the correct structure for NXOpen integration.
Expression update code uses the exact names from binary introspection.
To complete:
1. Set NX_MODEL_DIR to the Syncthing-synced model directory
2. Implement _open_session() with NXOpen.Session
3. Implement _solve() to trigger SOL 101
4. Implement _extract_displacement() and _extract_stress()
from .op2 results or NX result sensors
"""
def __init__(self, model_dir: str) -> None:
"""Initialize NXOpen solver.
Args:
model_dir: Path to directory containing Beam.prt, etc.
"""
self.model_dir = model_dir
self._session = None # NXOpen.Session
self._part = None # NXOpen.Part
logger.info("NXOpenSolver initialized with model_dir=%s", model_dir)
def evaluate(self, trial_input: TrialInput) -> TrialResult:
"""Full NX evaluation pipeline.
Pipeline:
1. Update expressions (beam_half_core_thickness, etc.)
2. Rebuild model (triggers re-mesh of idealized part)
3. Solve SOL 101
4. Extract mass (p173), displacement, stress
"""
raise NotImplementedError(
"NXOpenSolver.evaluate() is a template — implement on Windows "
"with NXOpen Python API. See docstring for pipeline."
)
def _update_expressions(self, trial_input: TrialInput) -> None:
"""Update NX expressions for a trial.
⚠️ Expression names are EXACT from binary introspection.
⚠️ `beam_lenght` has a typo (no 'h') — do NOT correct it.
This is the correct NXOpen code pattern (to be run on Windows):
```python
import NXOpen
session = NXOpen.Session.GetSession()
part = session.Parts.Work
# Update design variables
expressions = {
"beam_half_core_thickness": trial_input.beam_half_core_thickness,
"beam_face_thickness": trial_input.beam_face_thickness,
"holes_diameter": trial_input.holes_diameter,
"hole_count": trial_input.hole_count,
}
for expr_name, value in expressions.items():
expr = part.Expressions.FindObject(expr_name)
unit = expr.Units
part.Expressions.EditWithUnits(expr, unit, str(value))
# Rebuild (update model to reflect new expressions)
session.UpdateManager.DoUpdate(
session.SetUndoMark(NXOpen.Session.MarkVisibility.Invisible, "Update")
)
```
"""
raise NotImplementedError("Template — implement with NXOpen")
def _solve(self) -> bool:
"""Trigger NX Nastran SOL 101 solve.
```python
# Open the sim file
sim_part = session.Parts.OpenDisplay(
os.path.join(self.model_dir, "Beam_sim1.sim"), None
)
# Get the solution and solve
sim_simulation = sim_part.Simulation
solution = sim_simulation.Solutions[0] # First solution
solution.Solve()
# Check solve status
return solution.SolveStatus == NXOpen.CAE.Solution.Status.Solved
```
"""
raise NotImplementedError("Template — implement with NXOpen")
def _extract_mass(self) -> float:
"""Extract mass from NX expression p173.
```python
mass_expr = part.Expressions.FindObject("p173")
return mass_expr.Value # kg
```
"""
raise NotImplementedError("Template — implement with NXOpen")
def _extract_displacement(self) -> float:
"""Extract tip displacement from SOL 101 results.
Options (TBD — need to determine best approach):
1. NX result sensor at beam tip → read value directly
2. Parse .op2 file with pyNastran → find max displacement at tip nodes
3. NX post-processing API → query displacement field
Returns:
Tip displacement in mm.
"""
raise NotImplementedError(
"Template — extraction method TBD. "
"Options: result sensor, .op2 parsing, or NX post-processing API."
)
def _extract_stress(self) -> float:
"""Extract max von Mises stress from SOL 101 results.
⚠️ LAC LESSON: pyNastran returns stress in kPa for NX kg-mm-s
unit system. Divide by 1000 for MPa.
Options (TBD):
1. NX result sensor for max VM stress → read value directly
2. Parse .op2 with pyNastran → max elemental nodal VM stress
3. NX post-processing API → query stress field
Returns:
Max von Mises stress in MPa.
"""
raise NotImplementedError(
"Template — extraction method TBD. "
"Remember: pyNastran stress is in kPa → divide by 1000 for MPa."
)
def close(self) -> None:
"""Close NX session gracefully.
⚠️ LAC CRITICAL: NEVER kill NX processes directly.
Use NXSessionManager.close_nx_if_allowed() only.
If NX hangs, implement a timeout (10 min per trial) and let
NX time out gracefully.
"""
raise NotImplementedError("Template — implement graceful shutdown")
# ---------------------------------------------------------------------------
# Factory
# ---------------------------------------------------------------------------
def create_solver(
backend: str = "stub",
model_dir: str = "",
) -> NXStubSolver | NXOpenSolver:
"""Create an NX solver instance.
Args:
backend: "stub" for development, "nxopen" for real NX (Windows only).
model_dir: Path to NX model directory (required for nxopen backend).
Returns:
Solver instance implementing the NXSolverInterface protocol.
Raises:
ValueError: If backend is unknown.
"""
if backend == "stub":
return NXStubSolver()
elif backend == "nxopen":
if not model_dir:
raise ValueError("model_dir required for nxopen backend")
return NXOpenSolver(model_dir=model_dir)
else:
raise ValueError(f"Unknown backend: {backend!r}. Use 'stub' or 'nxopen'.")