Strains, Types of strains, Linear Strain, Bulk (or) Volume Strain, Shearing (or) Rigidity strain

Strains

Change in dimensions to original dimensions is known as Strain.

Types of strains

(1) Linear Strain

(2) Bulk (or) Volume Strain

(3) Shearing (or) Rigidity strain

(1) Linear Strain

The linear strain is defined as the ratio of change in length to the original length.

When a wire or bar is subjected to two equal and opposite forces, namely pulls, at its ends, there is an increase in the length. If the forces are tensile, the body is elongated. If the forces are compressive, the length is shortened in the direction of the forces. This is called the ‘linear strain’.

The linear strain is defined as the ratio of change in length to the original length. If the change (increase or decrease) in length is ‘ l ‘ in a wire or bar of original length L,

As the linear strain is ratio of lengths, it has no unit.

linear strain = Change in length/ original length 

(2) Bulk (or) Volume Strain

Volume strain is defined as the ratio of change in volume to the original volume. It has also no unit.

When a force is applied uniformly and normally to the entire surface of the body, there is a change in volume of the body, without any change in its shape. This strain is called ‘bulk or volume strain’.

If ‘v’ is the change in volume produced in a body of original volume ‘V’,

bulk or volume strain = Change in volume / original volume

(3) Shearing (or) Rigidity strain

When a force is applied parallel to one face of a body, the opposite side being fixed, there is a change in shape but not in size of the body. This strain is called the shearing strain.

Solids alone can have a shearing strain. It is measured by the angle of the shear ‘θ’ in radian.

Leave a Comment