Poissons Ratio - Definition, Formula, FAQs

Edited By Team Careers360 | Updated on Nov 11, 2024 07:25 PM IST

Define Poissons Ratio-

Poisson's ratio is the ratio of transversal expansion to axial compression, and it is symbolized by the Greek letter 'nu.' It is named after Simeon Poisson. The strain symbol is given by ε.

What is Poisson's ratio? Or how does Poisson's ratio work? Or Poisson's ratio definition:-

“The ratio of transverse contraction strain to longitudinal extension strain in the direction of the stretching force,” as described by Poisson. Here,

Compressive deformation is regarded as negative.
Tensile deformation is regarded as a positive.

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Define Poissons Ratio-
Poisson’s Formula
The Poisson's Ratio -

Poissons Ratio - Definition, Formula, FAQs

Symbol	Greek letter ’nu’,v
Formula	Poisson’s ratio= -lateral strain/ Longitudinal strain
Range	-0.1 to +0.5
Unit	Unitless
Scalar/vector	Scalar quantity

Also read -

Poisson’s Formula

In the middle, it will compress. If the rubber's original length and width are L and B, respectively, it will tend to compress laterally when tugged longitudinally. To put it another way, the length has increased by dL and the breadth has increased by dB.

In this instance,

The Poisson ratio formula is as follows:

ε_t= −dBε_l/B= −dL/L

where is ε_t transverse strain

ε_l is the longitudinal strain

Poisson's ratio=Transverse Strain/Longitudinal Strain

The Poisson's Ratio -

The change in dimension (length, breadth, area, etc.) divided by the original dimension is the strain.

Strain-

The term "strain" refers to how much an object has been stretched or deformed. When force is applied to an item, strain occurs. Strain is primarily concerned with the object's length change.

Lateral or transverse strain-

The ratio of the change in diameter of a circular bar of material owing to longitudinal deformation to its diameter is defined as lateral strain, also known as transverse strain. Because it is a ratio between two quantities of the same dimension, it is a dimensionless quantity. The lateral strain formula is given by multiplication of Poisson ratio and longitudinal strain.

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Longitudinal or axial strain-

A material elongates in the axial direction while contracting in the transverse direction when subjected to a tensile force P. Transverse strain is the contraction in the transverse direction, while a longitudinal strain is an elongation in the axial direction.

Poisson’s effect-

When a material is stretched in one direction, it compresses in the opposite direction, and vice versa. The Poisson's ratio is used to calculate the magnitude of this occurrence. When a rubber band is stretched, for example, it tends to get thinner.

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Poisson’s ratio value for different material-

It is the ratio of transverse contraction strain to longitudinal extension strain, in the direction of the stretching force. For tensile deformation, Poisson's ratio is positive. For compressive deformation, it is negative

Poisson's ratio is positive for tensile deformation.
It is negative for compressive deformation.

Despite the fact that the longitudinal strain is positive, the negative Poisson ratio indicates that the material will experience a positive transverse strain.

Range of Poisson's ratio-

For most materials, the Poisson's ratio is between 0 and 0.5.

For various materials, a few examples of Poisson ratio are presented below-

Material	Values
steel	0.27- 0.30
rubber	0.4999
concrete	0.1-0.2
clay	0.30-0.45
gold	0.42-0.44
cork	0.0
glass	0.18-0.3
copper	0.33
foam	0.10-0.50
stainless steel	0.30-0.31
cast iron	0.21-0.26