Calculate the ratio of transverse strain to axial strain for a material under loading.
Last updated: March 2026 | By ForgeCalc Engineering
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Poisson's ratio, named after Siméon Poisson, is a measure of the Poisson effect, where a material tends to expand in directions perpendicular to the direction of compression (or contract when stretched). It is a fundamental property in materials science and structural engineering.
Most stable, isotropic materials have Poisson's ratio values between 0.0 and 0.5. A value of 0.5 indicates a perfectly incompressible material (like rubber), while a value of 0.0 means the material does not expand laterally when compressed (like cork). Some rare materials, called auxetics, have negative Poisson's ratios.
Testing a steel rod:
Calculation: ν = |-0.00036 / 0.0012|
Final Answer: The Poisson's ratio is 0.300.
Most steels have a Poisson's ratio of approximately 0.27 to 0.30.
For standard isotropic materials, 0.5 is the theoretical upper limit. Values above 0.5 are possible for anisotropic materials (like some composites).
It means the material gets thicker when you stretch it. These are called auxetic materials and are used in specialized applications like body armor.
Yes, for isotropic materials, they are related via the Shear Modulus (G): G = E / (2(1 + ν)).
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