Coefficient of linear thermal expansion (CET), denoted by α, is indicative of how much a material will expand when heated. This expansion occurs as a result of increased vibrations of atoms owing of enhanced kinetic energy gained from the heat source. Consequently, the inter-atomic distance increases which ultimately causes the material to linearly expand.
CET is an inherent property of material and plays a significant role during material selection phase for fabrication jobs especially where high precision and accuracy is required over large thermal gradients.
Following table outline the consolidated results of the experiment. CTE using formula has also been calculated for each reading. Sample calculations are given thereafter. A graph for Extension (mm) against Temperature (oC) has also been plotted.
2) The large error in Aluminum up to 15558% is primarily due to human error. The readings may have not been noted accurately or the decimal place not marked in correct location. Systematic error can safely be ruled out since CTE of steel and brass and within acceptable error of 5.2% and 7.7% respectively
3) The slight error can be attributed to bias in noting down the temperature reading and extension precisely at the same time. Moreover, non-uniform heating, improper contact of temperature element and creep within the specimen due to multiple thermal cycles over time may have contributed to the variance in CTE. A dial gage itself is not an accurate device and electronic stain gages for measurement of extension can give more accurate results.
The results comply with the values taken from ASTM Handbook for metals for both steel and brass. Readings for Aluminum must be verified since the large error can only be attributed to human fault. For per degree rise in temperature, aluminum expands most followed by brass and then steel.