Poissons ratio

When a material is stretched in one direction it tends to get thinner in the other two directions

When a sample of material is stretched in one direction it tends to get thinner in the other two directions.

Poisson's ratio is the ratio of the relative contraction strain, or transverse strain normal to the applied load, to the relative extension strain, or axial strain in the direction of the applied load.

 

Poisson's Ratio can be expressed as

υ = - ε_t / ε_l             (1)

where

υ = Poisson's ratio

ε_t = transverse strain

 ε_l = longitudinal or axial strain

Strain can be expressed as

ε = dl/L             (2)

where

dl = change in length

L = initial length

For most common materials the Poisson's ratio is in the range 0 - 0.5.

Typical Poisson's Ratios fro some Common Materials

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