Metals/Alloys - Thermal Expansion and Poisson's Ratio
Expansion and Deformation
Because different materials can perform or behave dissimilarly to one another depending on not only their surroundings but also their purpose, it is important to understand how they will act and to what magnitude. Typical values for thermal expansion and Poisson's ratio of some commonly encountered steels has been provided in the table below. It should be noted that the most accurate information can be obtained from the manufacturer.
As temperature changes, materials have a tendency to respond with volume changes accordingly. In most cases materials will expand with an increase in temperature and contract with decreases. Although rare, some materials will contract with increased temperatures but such contractions are limited in size and only occur during certain temperature ranges. Expansion joints, additional loading and increased volume are some areas that may need to be considered when dealing with thermal expansion.
Poisson's ratio is the ratio of transverse contraction strain to longitudinal extension strain in the direction of an applied force. Tensile deformation is considered positive and compressive deformation is considered negative. If the material is stretched rather than compressed, it usually tends to contract in the directions transverse to the direction of stretching.