Poisson's Ratio

Ratio of lateral strain to axial strain in an axial loaded specimen. It is the constant that relates modulus of rigidity to Young's modulus in the equation:

Poisson

where E is Young's modulus; G, modulus of rigidity; and r, Poisson's ratio. The formula is valid only within the elastic limit of a material. A method for determining Poisson's ratio is given in ASTM E-132.