Coupling Kill Demo

Each component is safe. The combination is not.

Two domain oracles validate independently. Both return SURVIVE. A coupling oracle checks the interaction — and finds a fatal constraint violation that neither domain could detect alone.

Scenario

Aluminum structural frame (Al 6061-T6) carrying a PCB assembly that produces a measured ΔT of 60°C at the board–structure interface. The frame is designed at ambient temperature. The electronics are within their own thermal envelope. Nobody checked what the heat does to the aluminum.

PHASE 1 Individual Domain Validation

Structural Oracle

Domain: Mechanical Loading

✓ SURVIVE

Checked ULS bending capacity, Al 6061-T6 beam under combined loading

Assumptions Ambient temperature (20°C); material properties per ASM

Result Utilization 0.850 ≤ 1.00

Thermal Oracle

Domain: Thermal Envelope (Electronics)

✓ SURVIVE

Checked Thermal envelope per IPC-2152 at board-structure interface

Assumptions Natural convection; FR-4 substrate; ΔT measured at interface

Result ΔT 60°C ≤ 70°C limit

Both oracles report SURVIVE. A component-level review would approve this design. But the structural oracle assumed ambient temperature, and the circuit oracle validated only its own thermal envelope. Neither checked what the heat does to the structure.

PHASE 2 Cross-Domain Coupling Check

Coupling Oracle

Domain: Thermal ↔ Structural

✗ EXTINCT

Checked Thermal–structural coupling: circuit heat → aluminum yield derating

Assumptions Al 6061-T6 derating rate 0.3%/°C (ASM/MMPDS, ref. available on request); ΔT = 60°C from thermal oracle

Result Derated utilization 1.037 > 1.00

Yield strength

276 → 226.3 MPa

−18.0% from thermal derating

Utilization

0.850 → 1.037

Exceeds limit — EXTINCT

✗ DESIGN REJECTED

The structural oracle was correct: at ambient temperature, utilization is 0.850 — within limits.

The circuit oracle was correct: 60°C rise is within IPC-2152 thermal limits for the PCB assembly.

But the combination is fatal: 60°C heat reduces aluminum yield strength by 18%, pushing utilization to 1.037 — beyond the limit.

This failure exists only at the boundary between domains. No single-domain validator can catch it.

FCAL · AI proposes. Physics decides.

Fixed inputs for reproducibility. Derating model per ASM/MMPDS (reference available on request).