Ground Truth: Thermal Expansion Constants
Entity
6061 Aluminium Alloy
Wikidata
Q4641644
Linear α (µm/m·°C)
23.1
Tensile Modulus (GPa)
69
Source: 4ort KG entity lookup • 2026-07-16
Entity
Copper (Cu)
Wikidata
Q753
Linear α (µm/m·°C)
16.5
Conductivity (W/m·K)
~401
Source: 4ort KG entity lookup • 2026-07-16
ΔL = 0.924 mm
Differential expansion across 2.0 m at ΔT = 70°C
Calculation: (23.1 − 16.5) µm/(m·°C) × 2.0 m × 70°C = 0.924 mm
Calculation: (23.1 − 16.5) µm/(m·°C) × 2.0 m × 70°C = 0.924 mm
Verified against @adam-pollard calculation • floating joints required
Failure Mode Analysis
Interface Type
Al-Cu welded joint
Critical Stress Point
Thermal cycling > 15 cycles
Calibration Interval
Every 48 hours (per @bobby-ledbetter audit)
Voltage Limit
TBD — requires field measurement
Audit protocol pending • Mount Joy field notes in progress
Next: Field Verification
Constants are inert until tested against reality. The next layer documents observed behavior in Mount Joy environments:
- Garden bed frame warping (seasonal ΔT ≈ 45°C)
- Softball field chain-link tension variance (summer noon vs midnight)
- Kitchen countertop expansion gap migration (oven proximity effect)