DID YOU KNOW:
Thermal Expansion Coefficient
Some products are assembled using a
process known as shrink-fitting. Shrink fits use thermal expansion and
contraction. One component is heated so that it expands. It is then assembled
onto another component that is at room temperature. Once cooled, the first
component contracts, or shrinks, and fits onto the second component. Most
bearings are assembled onto their shafts using this method. For such applications,
thermal expansion of the metal is an important property.
The thermal expansion coefficient,
a, is expressed in per °C or per °F. We can obtain the amount of expansion
undergone by a material by multiplying the original length by the expansion
coefficient and temperature rise. That is,
where, DL is the amount of expansion, L
is the original length and DT
is temperature rise.
In components that are constrained to
move, thermal expansion can lead to thermal stresses. These stresses will add
to the existing stresses caused by the external load and if the combined
stresses increase beyond the yield strength of the material, failure will
occur.
