Definition of Strain:

Strain is defined as the change in length per unit length. It is a measure of the deformation of a material under the influence of an external force or stress. When a material is subjected to an external force, it undergoes a change in shape and size. The strain is a measure of the extent of this change in shape and size. It is usually expressed as a fraction or a percentage of the original length or size of the material.

Formula for Strain:

The formula for strain is given by:

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

Where,

Change in length = final length - original length

Original length = the length of the material before it is subjected to the external force

Types of Strain:

There are two types of strain:

1. Longitudinal Strain: When a material undergoes a change in length due to an external force applied parallel to its axis, it is called longitudinal strain.

2. Shear Strain: When a material undergoes a change in shape due to an external force applied perpendicular to its axis, it is called shear strain.

Unit of Strain:

Since strain is a ratio of lengths or sizes, it is a dimensionless quantity. However, it is often expressed in terms of microstrain or parts per million (ppm) to make it easier to compare the strains of different materials.

Uses of Strain:

Strain is an important parameter in the study of mechanics of materials. It is used to calculate the stress in a material, which is a measure of the internal forces that resist deformation due to external forces. Strain is also used to determine the elastic modulus, which is a measure of the stiffness of a material. It is also used in the design of structures and machines to ensure that they can withstand the stresses and strains they will be subjected to in use.