When we apply a force on a body it will undergo deformation and its length will increase or decrease. Length increases when the force is tensile and decreases when the force applied is compressive.   

The ratio of Change in dimension to the original dimension is called strain.

Strain = ε = Change in dimension/original dimension

There are two types of strains.

1.      Normal strain (Tensile, compressive and volumetric)

2.      Shear strain

Normal strain: It can be divided into three types.

a.      Tensile strain: When we apply a tensile force on a body its length increases.  The ratio of increase in length to the original length.

Tensile strain = ε_t = L – L₀ / L

Where L = Original length

  L₀ = new length

b.      Compressive strain: When we apply a compressive force on a body its length decreases. The ratio of decrease in length to the original length is called compressive strain.

Compressive strain = ε_c = L – L₀ / L

Where L = Original length

  L₀ = new length

c.       Volumetric strain: When we apply a force on all sides of a body its volume will decrease. The ratio of change in volume to the original volume is called volumetric strain.  

Volumetric strain = ε_v = V – V₀ / V

Where V = Original volume

V₀ = new volume 

Shear Strain: When we apply a tangential force on a body there is an angular displacement (θ), which measures the shear strain.

Shear strain = tan θ