When the deforming force is applied on the body, the body undergoes deformation and the body is said to be deformed or strained. Strain is defined as the ratio of change in configuration to the original configuration under the action of applied deforming force i.e.
Strain = change in configuration / original configuration
As strain is ratio of two similar quantities it has no unit.
Types of strain:
1. Longitudinal strain
It is defines as the ratio of change in length to original length under the action of applied deforming force. If a body of length ‘l’ undergoes change in length ‘dl’ then longitudinal strain is given by,
Strain = change in length / original length
= dl / l
2. Volumetric strain
It is defined as the ratio of change in volume to original volume under the action of deforming force. If a body having volume ‘v’ undergoes change in volume ‘dv’ then volumetric strain is given by,
Strain = dv / v
3. Tangential strain
This strain is produced when the body is acted by tangential stress. It is defined as the angle through which the face of the body moves from its original position.
tan o = x / l
therefore, o = x / l