Table of Contents
What Is Thermal Expansion?
Thermal expansion is the tendency of matter to change volume with temperature. Heated atoms vibrate more, maintaining greater separations. Engineers account for this in bridges (expansion joints), railways, and pipelines. Steel has alpha of ~12×10^-6 /K. A 100m bridge can expand 72mm over a 60°C seasonal range.
Most materials expand when heated, though water between 0-4°C contracts. Understanding expansion is critical for precision instruments, glass-to-metal seals, and preventing structural damage from temperature cycling.
Formulas
ΔL = L0 × α × ΔT
ΔA ≈ 2αΔT × A0
ΔV ≈ 3αΔT × V0
Coefficients
| Material | α (×10-6/K) |
|---|---|
| Aluminum | 23.1 |
| Copper | 17.0 |
| Steel | 12.0 |
| Glass | 8.5 |
| Invar | 1.2 |
FAQ
What is Invar?
A nickel-iron alloy with extremely low expansion (~1.2×10^-6/K), used in precision instruments and clock pendulums where dimensional stability is critical.