Answer to Question #3615 in Molecular Physics | Thermodynamics for Mike Coffin

Question

If I have steel washer in a room at a temperature of 70°F and I move it to a room at 100°F i know it will expand, but will the inside diameter of the washer increase or decrease and why?

Answer 1

Inside and outside diameters of the washer will increase with the temperature.When a substance is heated, its particles begin moving more and thus usually
maintain a greater average separation. Materials which contract with increasing
temperature are rare; this effect is limited in size, and only occurs within limited
temperature ranges. The degree of expansion divided by the change in temperature is
called the material's coefficient of thermal expansion and generally varies with
temperature.

Thermal expansion is also used in mechanical applications to fit parts over one
another, e.g. a bushing can be fitted over a shaft by making its inner diameter
slightly smaller than the diameter of the shaft, then heating it until it fits over
the shaft, and allowing it to cool after it has been pushed over the shaft, thus
achieving a 'shrink fit'. Induction shrink fitting is a common industrial method to
pre-heat metal components between 150 °C and 300 °C thereby causing them to expand
and allow for the insertion or removal of another component.