  # Types of Strains: Types of Strain in Engineering Physics [GATE Notes]

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Updated on: September 25th, 2023 According to different types of strain, when any external load is applied to the body, that load causes deformation as a change in dimension to the original dimension is known as strain. All the types of strain are a dimensionless quantity termed [M0 L0 T0]. Strain is a fundamental property of stress, or it can be said that stress is caused due to strain. Different types of stress are developed depending upon the types of strain.

Depending upon the stress induced in the body, different types of strain act on the body. The body’s shape is altered by the strain it experiences. Here we have discussed the strain and the different types of strain below.

## What are the Different Types of Strain?

A solid body has a set shape and size; if we want to modify that shape, we must exert force on the solid body. The direction and strength of the force acting on the body will cause stress; based on the sort of stress created, various types ofstrains will act on the body. The tension that the body experiences causes the body to change shape. According to Hooke’s law, the amount of stress caused in the body is precisely equal to the strain it produces. Stress and strain are connected. Therefore, the more stress that is caused, the more strain the body will produce.

Types of strain are based on the nature of load, stress, and also on the property of the material. But material property is not the primary factor. Let us discuss the different types of strain.

• Tensile strain
• Compressive strain
• Volumetric strain
• Shear strain
• Thermal strain

## Tensile Strain

In this type of strain, when increment length deformation occurs in the direction of load or reduction of the cross-section in the direction of applied load, it is known as tensile strain, and that load or stress is called tensile load or tensile stress. In this term, we use the ratio of increased length to the original length. The nature of this deformation is positive.

 Tensile Strain = Increase in length/Original length

Due to tensile strain, the cross-section’s actual area changed as the cross-section’s original area minus the cross-section’s deformed area.

## Compressive Strain

In this type of strain, when length decrement deformation occurs in the direction of load or increment of the cross-section in the direction of applied load, it is known as compressive strain. That load or stress is called compressive load or compressive stress. In this term, we use the ratio of decrease in length to the original length. The nature of this deformation is negative.

 Tensile Strain = Decrease in length/Original length

Due to compressive strain, the actual area of the cross-section changed as the original area of the cross-section plus a deformed cross-section area.

## Volumetric Strain

In this type of strain, when complete body volume gets deformed due to external load as the ratio of change in volume to the original volume. Volumetric strain is considered in all three directions as linear, longitudinal, and lateral direction. This volumetric strain is inversely proportional to the Poisson’s ratio.

 Tensile Strain = Change in volume/Original volume
• Volumetric strain or (εv) = δV/V
• εv = εx + εY + εZWhere; εx = Strain in X- direction
• εY = Strain in Y- direction
• εZ = Strain in Z- direction

We know as εx = ∂u/∂x ; εy = ∂u/∂y and εz = ∂u/∂z

From this εv = { ∂u/∂x + ∂u/∂y + ∂u/∂z }

Alsoεv = [ σ123/E ][1-2μ ]

Where μ is Poisson’s ratio.

## Shear Strain

In this type of strain, when the applied external load changes the angles between the line to the original line angle, that deformed angle is called a shear angle, and this phenomenon is called shear strain. In the figure in the x direction, deformation is anticlockwise (α1), and deformation is clockwise from the y direction (α2). At X- direction

Tan α1 = dv/∂x

At Y- direction

Tan α1 = du/∂y

Or

At XY- direction

𝛾XY = dv/∂x + du/∂y

## Thermal Strain

In this types of strain, when thermal changes occur as temperature increases or temperature decreases, the body will expand or contract, by which these changes occur in the dimension known as thermal strain. It is denoted by delta (Δ). Thermal strain depends on the expansion coefficient, which is different for different materials.

 Thermal Strain = L.α. Δt/L

Where L = Original length of the specimen

α = Thermal coefficient

Δt = Tm – To or (measured temperature – Nominal temperature)

We know, αAluminum > αBrass > αCopper > αSteel

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