Strain: When a specific force is applied to an object, people wonder about how the object will move subsequently. However, we fail to examine how the force can impact the object’s structure. Bridges are a wonderful illustration. When automobiles move across a bridge, their weight creates a downward pull. Therefore, bridges are subjected to stress tests to ensure that they can endure high pressure without cracking. The internal force per unit area is undoubtedly referred to as stress.

In simple words, strain is a measure of the amount of deformation that occurs on an object as a result of force. Read the following article for more information on strain meaning, strain formula and types of strain. Continue reading this article for more information on Strain, Formula and types.

What is Strain?

It is the ratio of change in dimension of a body to the original dimension of the same body before the deforming force was applied on it. It is the physical quantity that quantifies the deformation of an object.

In physical sciences and engineering, strain describes relative deformation or change in shape and size of elastic, plastic, and fluid materials under applied forces. The deformation, expressed by strain, arises throughout the material as the particles (molecules, atoms, ions) of which the material is composed are slightly displaced from their normal position.

Strain Formula

It is defined as the ratio of deformation produced in the dimensions of a material and its original dimensions. Since strain is a change in shape and size to the original shape and size of a given body, it can be written as:

\({\rm{Strain = }}\frac{{{\rm{ Change}}\,{\rm{in}}\,{\rm{dimension }}}}{{{\rm{ initial}}\,{\rm{dimension }}}}\)

What are the Types of Strain?

1. Longitudinal Strain

When the deforming force produces a change in length of the given body in the direction of force, then the strain produced in the body is called Longitudinal strain. It is equal to the ratio of change in length of a body to its original length.

\({\rm{Longitudinal}}\,{\rm{strain}} = \varepsilon = \frac{\delta }{L}\)

Longitudinal strain can be categorized into:

(i) Compressive Strain

When the deforming force tends to increase the area of the body and decrease the length of the body, the strain produced is called compressive strain.

(ii) Tensile Strain

When the deforming force tends to decrease the area of the body and increase the length of the body, the strain produced is called tensile strain.

2. Lateral Strain

When the deforming force produces a change in length of the given body perpendicular to the direction of force, then the strain produced in the body is called Lateral strain.

3. Volumetric Strain

When the deforming force produces a change in volume of the given body, then the strain produced in the body is called Volumetric strain. It is equal to the ratio of change in volume of a body to its original volume.

\({\rm{Volumetric}}\,{\rm{strain}} = \frac{{dV}}{V}\)

4. Shearing Strain

When the deforming force produces a change in the shape of a body without any change in its volume, then the strain produced in the body is called the Shearing strain. It is the angular displacement of the plane perpendicular to the fixed surface. The angle in radians through which a force is displaced on applying tangential deforming stress is called shearing strain.

\({\rm{Shear}}\,{\rm{strain}} = \theta = \frac{{\Delta L}}{L}\)

Unit of Strain

Strain is the ratio of the change in dimension, which can be the length or area or volume of the given body, under the action of external force to the original dimension of the body. Since it is the ratio of two quantities having the same dimensions and units, so the strain is a dimensionless quantity without any unit.

Solved Problems on Strain

Q.1. A sample of biological material is loaded into a material-testing machine. The material is \({\rm{2}}\,{\rm{cm}}\) long in its unloaded state. However, under a tensile force of \({\rm{6000}}\,{\rm{N,}}\) it stretches to a length of \({\rm{2}}{\rm{.0004}}\,{\rm{cm}}\) due to this force. What is the strain in the specimen when it is stretched this much?
Ans: Initial length \((L) = 2\;{\rm{cm}}\)
Final Length \(\left( {{L^\prime }} \right) = 2.0004\;{\rm{cm}}\)
Change in length \( = {L^\prime } – L = 0.0004\;{\rm{cm}}\)
\({\rm{strain}} = \varepsilon = \frac{{{L^\prime } – L}}{L} = \frac{{0.0004}}{{2.0004}}\)
\(\varepsilon = 0.0002\)

Q.2. A girl stretches her rubber band of length \(6\;{\rm{cm}}\) such that its length increases by \({\rm{3}}\,{\rm{mm}}\). Compute the strain.
Ans: Original length of rubber band \((L) = 6\;{\rm{cm}} = 0.06\;{\rm{m}}\)
Change in length \((x){\rm{ = 3}}\,{\rm{mm = 0}}{\rm{.003}}\,{\rm{m}}\)
The strain is given by \({\rm{strain}} = \varepsilon = \frac{x}{L} = \frac{{0.003}}{{0.06}}\)
\(\varepsilon = 0.05\)

Frequently Asked Questions on Strain

Here we have provided frequently asked questions on strain:

Q.1. What is the best definition of a strain?
Ans: Strain is the deformation produced in a body due to the force applied to it, divided by the initial dimension of the body.

Q.2. What is strain explain?
Ans: When an external force is applied to a body and the force applied is large enough, it produces deformation. Depending on the nature of the material, these deformations may be large or small. This quantification of the deformation of a material is called Strain. For example, Linear strain occurs as a result of a change in the object’s length. Compressive or tensile stresses produce linear strain. A shear strain occurs as a result of a change in the orientation of the object’s molecules.

Q.3. What is the medical term for strain?
Ans: A strain is when a muscle is stretched too much and tears. It is also called a pulled muscle. A strain is a painful injury. It can be caused by accident, overusing a muscle, or using a muscle in the wrong way.

Q.4. What causes strain?
Ans: Strain is the brought in a system as a result of applied stress. For example, when a material is loaded with a force, it produces stress, which then causes the material to deform, and this deformation is measured in terms of strain. Force applied along the length of a body may lead to a longitudinal strain, or a force causing a volume change can lead to a volumetric strain.

Q.5. What is a DNA strain?
Ans: A DNA strain or strand stands for nucleic acid that carries the genetic information in cells and some viruses, consisting of two long chains of nucleotides twisted into a double helix and joined by hydrogen bonds between the complementary bases.

Q.6. Which is worse, sprain or strain?
Ans: Strains affect the tendons, and sprains affect the ligaments. A strain is sometimes called a “pulled muscle.” Depending on the level of muscle strain, it may heal within a few weeks, but reinjury can happen. A sprain is when ligaments stretch too far or tear. A sprain may take \(4–6\) weeks to heal or sometimes longer. Hence sprains, in general, can be worse, but ultimately it depends upon the damage caused in each case.

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