Poisson’s Ratio

It has been found experimentally that when a body is stressed within elastic limit, the lateral strain bears a constant ratio to the linear strain, Mathematically,

Lateral strain/Linear strain= Constant

This constant is known as Poisson’s ratio and is denoted by 1/m or μ.
Following are the values of Poisson’s ratio for some of the materials commonly used in engineering practice.

Poisson’s Ratio (υ) = – lateral strain / Axial strain

= – εx/εz

= -εy/εz

= – [∆d / do] / [∆l/ lo]

εx =εy = – υ εz               The negative sign is added to yield a positive value for υ