Poisson's ratio

Poisson's ratio (nu) is a measure of the Poisson effect, that describes the expansion or contraction of a material in directions perpendicular to the direction of loading. The value of Poisson's ratio is the negative of the ratio of transverse strain to axial strain. For small values of these changes, is the amount of transversal expansion divided by the amount of axial compression. Most materials have Poisson's ratio values ranging between 0.0 and 0.5. Incompressible materials such as rubber, have a ratio near 0.5. The ratio is named after the French mathematician and physicist Siméon Poisson.