The Poisson Ratio is the negative ratio of transverse to axial strain. In fact, when a sample object is stretched (or squeezed), to an extension (or contraction) in the direction of the applied load, it corresponds a contraction (or extension) in a direction perpendicular to the applied load. The ratio between these two quantities is the Poisson's ratio.
Applicable units are those of quantitykind:PoissonRatio
http://en.wikipedia.org/wiki/Poisson%27s_ratio
The Poisson Ratio is the negative ratio of transverse to axial strain. In fact, when a sample object is stretched (or squeezed), to an extension (or contraction) in the direction of the applied load, it corresponds a contraction (or extension) in a direction perpendicular to the applied load. The ratio between these two quantities is the Poisson's ratio.
$\mu = \frac{\Delta \delta}{\Delta l}$, where $\Delta \delta$ is the lateral contraction and $\Delta l$ is the elongation.
http://www.iso.org/iso/catalogue_detail?csnumber=31889