# Strain | Mechanical Properties of Solids

## Stress | Mechanical Properties of Solids-

Before you go through this article, make sure that you have gone through the previous article on Stress & Its Types.

We have learnt-

• Under the action of deforming force, the original configuration of the body changes.
• The restoring force developed inside the body tries to restore its original configuration.
• The restoring force per unit area of the body is called as stress.
• The effect of stress is to produce distortion or change the configuration of the body.

## Strain-

In mechanical properties of solids, strain is defined as-

 The ratio of the change in configuration to the original configuration is called as strain.

Mathematically, ### Characteristics of Strain-

• It is a unitless and a dimensionless quantity as it is a ratio of two like quantities.
• It is a scalar quantity.
• It measures the degree of deformation of the body.

## Types of Strain- Let us discuss all types of strain one by one in detail.

### 1. Longitudinal Strain-

• This type of strain is produced when the body is under the tensile stress or compressive stress.
• It is defined as the ratio of change in length to the original length of the body. ### 2. Volume Strain-

• This type of strain is produced when the body is under the volume stress.
• It is defined as the ratio of change in volume to the original volume of the body. Here, negative sign shows that the volume decreases when the body is under the volume stress.

### 3. Shear Strain-

• This type of strain is produced when the body is under the shearing stress.
• It is defined as the angle (θ) through which the face of a body originally perpendicular to the fixed face is turned. From the figure,

#### tanθ = x/L

If θ is small, we have-