Scope:

Size of an object changes with a change in the ambient temperature. The coefficient of Linear Thermal Expansion (CLTE) measures the rate at which a given material expands as a function of temperature. This test is important to select thermally stable material for designing parts of different equipment and machines. Knowledge about relative expansion/contraction features of two materials in contact is utilized to use the tested materials successfully. 

Test Procedure:

A thermomechanical analyzer (TMA) is employed for the test. The material specimen is placed in the holder at ambient temperature, and the specimen’s length is measured. Next, the specimen is cooled to a specific temperature and then heated again by increasing the temperature inside the furnace. The test specimen is heated at a particular rate over the desired temperature range. CLTE versus temperature graph is drawn to obtain a curve. Dimensional changes in a specimen as a function of temperature can also be measured by using a dilatometer. The specimen is placed in the holder inside the dilatometer tube and is then heated. The overhead measuring compartment gauges change in dimension of the specimen.

Specimen size:

The test specimen to be used for TMA can be anywhere between 2 and 10 mm in length and a maximum of 10 mm in breadth and should be flat at both ends. The test specimen should be approximately 75 mm in length and 12.7 mm in breadth for a dilatometer.

Data:

The coefficient of linear thermal expansion (CLTE) is calculated and plotted between the desired temperature ranges to give the desired curve.