18.11: Thermal Strain
Thermal strain is a concept that arises when we consider how temperature changes affect structures. Unlike the conventional assumption that structures remain constant under load, real-world scenarios often involve temperature fluctuations that can significantly impact these structures. Consider a homogeneous rod with a uniform cross-section resting freely on a flat horizontal surface. If the rod's temperature increases, the rod elongates. This elongation is proportional to the temperature change and the rod's original length.
The proportionality constant in this relationship is a material-specific characteristic known as the coefficient of thermal expansion. It represents the amount by which a unit length of a material will change for each degree of temperature change. The coefficient can be expressed in units per degree Celsius.
As the rod deforms due to the temperature change, it results in elongation. The deformation is associated with thermal strain. It is important to note that stress is not necessarily related to thermal strain. It distinguishes thermal strain from mechanical strains, which usually involve associated stresses. Understanding thermal strain is essential in designing and analyzing structures subjected to temperature changes. The thermal strain must be ensured for the safety and integrity of structures under different environmental conditions. It can significantly affect the performance and lifespan of various structures.
