Poisson's Ratio Calculator Formula

Understand the math behind the poisson's ratio calculator. Each variable explained with a worked example.

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Formulas Used

Poisson's Ratio (nu)

nu = lateral_strain / axial_strain

Variables

VariableDescriptionDefault
lateral_strainLateral Strain (transverse)(mm/mm)0.0003
axial_strainAxial Strain (longitudinal)(mm/mm)0.001

How It Works

Poisson's Ratio

When a material is stretched, it contracts laterally. Poisson's ratio quantifies this coupling.

Formula

nu = -epsilon_lateral / epsilon_axial

Since lateral strain is opposite in sign to axial strain, nu is positive. Most metals have nu between 0.25 and 0.35. Steel is approximately 0.30, aluminium 0.33, rubber approaches 0.50 (incompressible). Cork is near zero.

Worked Example

A steel rod under tension shows 0.001 axial strain and 0.0003 lateral contraction.

lateral_strain = 0.0003axial_strain = 0.001
  1. 01nu = 0.0003 / 0.001 = 0.300
  2. 02This is a typical value for structural steel.

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