Strain and it's types

Strain is defined as the ratio of change in dimensions of the body to the original dimensions of body.

Strain = Change in dimensions (Length or Area or Volume) / Original dimensions (Length or Area or Volume)

It has no units and dimensions.

Types of strains: Strain has three types :

(1) Longitudinal strain

(2) Volumetric strain

(3) Shear strain.

(1) Longitudinal strain: It is defined as the increase or decrease in length per unit original length of body when deformed by an external force. This strain is also called linear strain.
If l is change (increase or decrease) in length of body on applying deforming force and L is original length of body, then the longitudinal strain is given by,

Longitudinal strain = Change in length (l)/ Original length (L)

It has no units and dimensions.

(2) Volumetric strain: It is defined as the change (increase or decrease) in volume per original volume of body when deformed by an external force.

If ΔV is change (increase or decrease) in volume of body and V is original volume of body then the volumetric strain is given by

Volumetric strain = Change in volume (ΔV)/
Original volume (V)

It has no units and dimensions.

(3) Shear strain: It is defined as the angle (θ) in radian through which a line originally perpendicular to a fixed face gets turned on applying tangential deforming force. The angle (θ) is called angle of shear. Shear strain is also dimensionless quantity.