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Thermal expansion

Most materials expand when temperature increases. The length increase is approximately proportional to the original length, the temperature change, and the material's linear expansion coefficient α\alpha. This must be accounted for in structures with large temperature swings, like bridges and pipelines.

ΔL=α L0 ΔT\Delta L = \alpha\, L_0\, \Delta Tlength increase with temperature change

Symbols

α\alphalinear expansion coefficient1/K
L0L_0original lengthm
ΔT\Delta Ttemperature increaseK

Example

Copper busbar 3 m, α=17×10−6\alpha = 17\times 10^{-6}/K, heated 75 K:

ΔL=17×10−6⋅3⋅75≈3.825\Delta L = 17\times10^{-6}\cdot 3\cdot 75 \approx 3.825 mm.

Expansion joints in bridges and pipes exist precisely to handle this length change without building up stress.
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