Thermal expansion ¾ Increase in temperature may cause dimensional changes. ¾ Linear coefficient of thermal expansion (α) defined as the change in the dimensions of the material per unit length.
α=
l f − l0 l 0 (T f − T0 )
=
ε Δl = l 0 ΔT ΔT
¾ α has units as (˚C)-1. ¾ α values: for metals 5-25x10-6 for ceramics 0.5-15x10-6 for polymers 50-400x10-6