# What is Strain – Strength of Material?

What is strain?, this is a simple and common question generally asked by a person who goes to study about strain in strength of material. In this post I will try my level best to explain you about strain.

### What is strain?

When an external force is applied on a body, there is some change occur in the dimension of the body. The ratio of this change of dimension in the body to its actual length is called strain.

**For example:**if you have a bar of length

**l and an external force**

**P**

**is applied on the bar, then there is some change in the length of the bar. Let the change produced in the bar is dl. Then the strain is the ratio of this change in the length to the original (actual) length. Strain is dimensionless quantity.**

Mathematically,

strain= (change in length)/(original length)

e= dl/l

e= dl/l

### Types of strain:

Strain in mechanics is of four types and these are:

**1. Tensile strain:**The strain produced in a body due to tensile force is called the tensile strain. The tensile force is always results in increment of the length and decrease in the cross section area of the body. In this case the ratio of the increase in length to the original length is called tensile strain.

**2. Compressive strain:**The strain appears due to the compressive force is called compressive strain. In compressive force there is a decrease in the dimension of the body. So the ratio of the decrease in the length of the body to the original length is called compressive strain.

**3. Volumetric strain:**The ratio of the change in the volume of a body to the original volume is called the volumetric strain. In volumetric strain there is a change in the volume of the body due to application of the external forces.

**4. Shear strain:**The strain which is produced in a body due to shear force is called shear strain.

This is all about what is stress, types of stress and definition of each type of strain in strength of materials.