# Longitudinal Strain, Definition of Longitudinal Strain, Longitudinal Strain Meaning (For CBSE, ICSE, IAS, NET, NRA 2022)

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# Longitudinal Strain

## Strain

• According to the strain definition, it is defined as the amount of deformation experienced by the body in the direction of force applied, divided by initial dimensions of the body.
• The relation for deformation in terms of length of a solid is given below.

where,

• = the strain due to stress applied
• = the change in length
• L = original length of the material.
• The strain is a dimensionless quantity as it just defines the relative change in shape.
• There are two types of strain and they are:
• Longitudinal strain
• Lateral strain

## Definition of Longitudinal Strain

• A longitudinal strain is defined as Change in the length to the original length of an object
• If there is a change in the length of a body due to the applied force, then the strain is called longitudinal strain.
• It is the ratio of the change in length of a body to the original length of the body. It is measured by the change in length per unit length. This kind of strain is also called torsion strain.
• It is caused due to longitudinal stress and is denoted by the Greek letter epsilon .

### Longitudinal Strain Formula

• Let the initial length of a body = L
• The change in length due to applied force (Figure)

Longitudinal strain

• If the length increases due to tensile stress, the corresponding strain is called tensile strain.
• If the length decreases due to compressive stress, the strain is called compressive strain.
• The longitudinal strain, e, is measured in terms of the changes in the lengths of lines.

### Longitudinal Strain Unit

They cancel each other, making it unit less or dimensionless quantity.

## Longitudinal Strain Meaning

• Stress and strain are like two sides of a coin.
• It is important to know their behaviour at microscopic scales.
• All solids are elastic by nature. Atoms or molecules constitute them. Each atom or molecule is surrounded by neighboring atoms or molecules.
• Each atom or molecule surrounded by neighboring atoms or molecules are bonded together by intermolecular forces and stay in equilibrium.
• When a deforming force or external force is applied, their intermolecular or inter atomic distances vary.
• By conclusion, a restoring force will be generated to attain back the equilibrium, thereby regaining original size and shape.
• When a body is under load, it will extend in the direction of the stress (longitudinal strain) and contract in the transverse or lateral direction (lateral strain) , in case of longitudinal tensile stress. As a result, a restoring force will be generated to attain back the equilibrium, thereby regaining the original size and shape.

### Cylinder with L as Length and D as the Diameter

• What happens to the cylinder when an equal force is applied such that it is perpendicular to the cross-sectional area? The answer is there will be a change in its length as well as in diameter.
• The length will increase from L to and Diameter will reduce from D to D-.
• So, the change in dimension to the original dimension is defined as strain. It tells the amount of stress an object is experiencing.
• When the object is stretched, the restoring force is known as tensile stress. When the object is compressed, the restoring force is known as compressive stress.
• So, in both ways, there will be a considerable change in the length of the object, say, cylinder.
• So, we can define “longitudinal strain as Change in the Length to Original Length L.”

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