Strain:

Strain is a measure of the deformation produced in a body as a result of an external (deforming) force applied on it. It is defined as the fractional change in the dimensions of the body under stress. That is, strain is the change in dimension per unit dimension of the body. Because strain is the ratio of two same quantities, it is dimensionless quantity.

Further, corresponding to three different types of stresses, we define the following three kinds of strains:

Linear Strain

It is defined as the ratio of the increase in length (Δ l) to the original length (l) of the body when a longitudinal deforming force (Figure) is applied on it. As per the Mathematically equation, we write:

Linear Strain = Change in Length (Δ l ) /Original Length (l )

Figure: Linear Strain