Bimetallic strip · CTE differential bending · Thermal stress σ = EαΔT
σ = E · α · ΔT (bar fixed at both ends)
Interactive bimetallic strip simulation exploring how different thermal expansion coefficients cause bending when heated or cooled. Also calculates thermal stress in a constrained bar.
A bimetallic strip is made of two metals bonded together with different thermal expansion coefficients (α). When heated, the metal with higher α expands more, causing the strip to bend. Curvature depends on ΔT, strip thickness, and the ratio of expansion coefficients.
Adjust the temperature with the slider. Watch the strip bend toward the metal with lower expansion coefficient. Toggle the constrained-bar mode to see thermal stress build up when expansion is prevented.
Bimetallic strips are used in thermostats, circuit breakers and old car turn signals. The original thermostat design by Warren Johnson (1883) used exactly this principle — and similar designs are still used in billions of devices.