An Overview About Stress and Strain

Stress and strain are two important concepts of physics. This article aims to explain why some objects are more changeable than others. Deformation is defined as the changing of an object’s shape caused by the application of force. External forces may cause the thing to experience it, such as squeezing, squashing, twisting, shearing, ripping, and dragging the objects apart.

The spring is somewhat squeezed, and it adjusts the intermolecular forces. These displaced molecules are brought back to their respective equilibrium potions by the restoring forces created in the spring. 

What is elasticity? 

Intermolecular forces occur when atoms and molecules in a solid are organised, so that neighbouring molecules exert a force on each other. After removing the deforming pressures (length, shape or volume), the body returns to its original structure. This is how the body shows elasticity.

Elasticity is the property of a solid body that allows it to revert to its original configuration (shape and size) whenever an external deforming force has been eliminated.

Stress 

Stress is a force per unit area generated into materials due to externally applied forces, unequal heating, and persistent deformation, allowing for accurate description and prediction of elastic, plastic, or fluid behaviour.

The following formula calculates stress:

σ = F/A

Where σ is the applied stress, F is the applied force, and A is the force application area.

The stress unit is N/m2.

Stress types

There are two forms of stress that can be applied to matters.

Tensile stress

The type of stress that elongates a substance along the axis of the applied force is called tensile stress. The magnitude of pressure applied along an elastic rod is split by the cross-sectional area of the rod in a direction perpendicular to the applied force to calculate tensile stress. Tensile implies that the matter on which force has been applied is under tension and that the forces were acting on it to expand it.

Compressive stress

A force that enables a substance to deform and occupy a smaller volume is known as compressive stress. A substance is said to have been under compression whenever subjected to compressive stress. 

Strain

The amount of distortions generated by a body in the direction of applied forces exerted by the body’s beginning dimensions is known as strain.

The following formula expresses the deformation of a solid in the proportion to its length:

ε = δl/ L

Where l is the change in length of the matter due to the strain caused by an applied stress, and L is its initial length.

As it describes the relative change in the shape of a body, strain is a dimensionless quantity.

Types of strain

Tensile strain

When tensile stress causes a change in a body’s length (or area), then it is known as tensile strain.

Compressive strain

When there is a change in the length (or area) of a body caused due to compression, it is called compressive strain.

Hooke’s Law

While English scientist Robert Hooke researched springs and elasticity in the 19th century, he noticed many materials exhibited a similar feature when the stress-strain relationship was examined. Hooke’s Law established a linear zone in which the force required to stretch a matter was proportional to its length.

Hooke’s Law states that even a material’s strain is equal to the applied stress within its elastic limit.

Hooke’s Law is frequently represented mathematically as:

F = –k.x

Here F is the force, x is the length of the extension, while k is the proportionality constant, also referred to as the spring constant in N/m.

Conclusion

Stress and strain are important parts of physics. In engineering and science, the importance of stress and strain for materials has been used to depict the stress-strain relationship. This stress and strain relationship is determined by gradually increasing the load on a test object while monitoring deformation and then calculating stress and strain from the results. The results reflect many properties of materials, such as Young’s modulus, yield strength, and final tensile strength.