Question Details

The value of Poisson’s ratio lies between

Options

A

-1 to 1/2

B

-3/4 to -1/2

C

-1/2 to 1

D

1 to 2

Correct Answer :

-1 to 1/2

Solution :

The correct option is -1 to 1/2.

Poisson's ratio (σ) is defined as the ratio of lateral strain to longitudinal strain for a given material under tensile stress. The theoretical limits of Poisson's ratio can be determined using the relations between elastic constants.

The relationship between Young's modulus (Y), Bulk modulus (K), and Poisson's ratio (σ) is given by:

Y = 3 K ( 1 - 2 σ )

Similarly, the relationship between Young's modulus (Y), Shear modulus (η), and Poisson's ratio (σ) is given by:

Y = 2 η ( 1 + σ )

Since the elastic moduli (Y, K, and η) must always be positive values for physical stability, we can analyze the expressions inside the brackets:

1. From the first equation, since Y and K are positive:
1 - 2 σ > 0
2 σ < 1
σ < 1 2

2. From the second equation, since Y and η are positive:
1 + σ > 0
σ > - 1

Combining these two inequalities, the theoretical range for Poisson's ratio (σ) is:
- 1 < σ < 1 2

Thus, the value of Poisson's ratio lies between -1 to 1/2.

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