# bracket_pareto_3obj

Three-objective Pareto optimization: minimize mass, minimize stress, maximize stiffness

**Generated**: 2025-12-06 14:43
**Protocol**: Multi-Objective NSGA-II
**Trials**: 100

---

## 1. Engineering Problem

Three-objective Pareto optimization: minimize mass, minimize stress, maximize stiffness

---

## 2. Mathematical Formulation

### Design Variables

| Parameter | Bounds | Units | Description |
|-----------|--------|-------|-------------|
| `support_angle` | [20, 70] | degrees | Angle of support arm relative to base |
| `tip_thickness` | [30, 60] | mm | Thickness at bracket tip where load is applied |


### Objectives

| Objective | Goal | Extractor | Weight |
|-----------|------|-----------|--------|
| mass | minimize | `extract_mass_from_bdf` | 1.0 |
| stress | minimize | `extract_solid_stress` | 1.0 |
| stiffness | maximize | `extract_displacement` | 1.0 |


### Constraints

| Constraint | Type | Threshold | Units |
|------------|------|-----------|-------|
| stress_limit | less_than | 300 | MPa |


---

## 3. Optimization Algorithm

- **Protocol**: protocol_11_multi
- **Sampler**: NSGAIISampler
- **Trials**: 100
- **Neural Acceleration**: Disabled

---

## 4. Simulation Pipeline

```
Design Variables → NX Expression Update → Nastran Solve → Result Extraction → Objective Evaluation
```

---

## 5. Result Extraction Methods

| Result | Extractor | Source |
|--------|-----------|--------|
| mass | `extract_mass_from_bdf` | OP2/DAT |
| stress | `extract_solid_stress` | OP2/DAT |
| stiffness | `extract_displacement` | OP2/DAT |

---

## 6. Study File Structure

```
bracket_pareto_3obj/
├── 1_setup/
│   ├── model/
│   │   ├── Bracket.prt
│   │   ├── Bracket_sim1.sim
│   │   └── Bracket_fem1.fem
│   ├── optimization_config.json
│   └── workflow_config.json
├── 2_results/
│   ├── study.db
│   └── optimization.log
├── run_optimization.py
├── reset_study.py
├── README.md
├── STUDY_REPORT.md
└── MODEL_INTROSPECTION.md
```

---

## 7. Quick Start

```bash
# 1. Discover model outputs
python run_optimization.py --discover

# 2. Validate setup with single trial
python run_optimization.py --validate

# 3. Run integration test (3 trials)
python run_optimization.py --test

# 4. Run full optimization
python run_optimization.py --run --trials 100

# 5. Resume if interrupted
python run_optimization.py --run --trials 50 --resume
```

---

## 8. Results Location

| File | Description |
|------|-------------|
| `2_results/study.db` | Optuna SQLite database |
| `2_results/optimization.log` | Structured log file |
| `2_results/pareto_front.json` | Pareto-optimal solutions |

---

## 9. References

- [Atomizer Documentation](../../docs/)
- [Protocol protocol_11_multi](../../docs/protocols/system/)
- [Extractor Library](../../docs/protocols/system/SYS_12_EXTRACTOR_LIBRARY.md)