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
= – [∆d / do] / [∆l/ lo]
εx =εy = – υ εz The negative sign is added to yield a positive value for υ