Mercury 0.000 059 9Aluminium 0.000 022 1Brass 0.000 018 9Copper 0.000 017 1Iron 0.000 011 7Cast Iron 0.000 011 2Steel 0.000 0119Invar 0.000 001 0Taking aluminium as an example: one mm of aluminium expands 0.000 022 1 mm for 1 deg C rise in temperature. One metre of aluminium expands 0.000 022 1 metre for 1 deg C rise in temperature. If the temperature rise is doubled the expansion (increase in length) will be doubled also, e.g. one mm of aluminium will expand 0.000 022 1 multiplied by 2, equals 0.000 044 2 mm for a 2 deg C rise n temperature, and a two mm length of aluminium will also expand 0.000 022 1 multiplied by 2 for 1 deg C rise in temperature.We are now able to calculate the increase in length (linear expansion) of a material and the following examples show the methods used. One example of cubical expansion is also given.Example. Calculate the gap required in a piston ring to allow for expansion, under working conditions, given the following data:Cylinder bore diameter, 60 mmNormal temperature, 18 deg CWorking temperature, 162 deg CCoefficient of expansion, cast iron, 0.000 011 2 per degree CRing circumference = 60 x mm (linear measurement) Ring expansion = Circumference x coefficient of expansion x temperature rise = 60 x x 0.000 011 2 x (162 –18) mm = 0.3041 mmTherefore the gap necessary to allow for expansion should be at least 0.3 mm. In practice, however, the cylinder expands also and the ring gap would be rather less than this figure.Liquid and gases have no definite form, and when heated cubical expansion only takes place. ...
