The calculation is in my comment. Although something I am not entirely sure of is whether this value should be halved? Either way poissons ratio is the linear relationship between a load applied in a certain direction, and the strain experienced in a direction orthogonal to the direction of the load, which is what that calculation of 6400/1.66e5 is describing.nIf it is not clear to you I would recommend starting with structural steel, setting up two definitions, one that uses isotropic definitions, and one that use anisotropic definitions, and applying a unit load to a cube, or prism of some nominal shape. Adjust the anisotropic values until you see correlation with the isotropic definition.n