Difference Between Deformation and Strain

Deformation vs Strain | Elastic Deformation and Plastic Deformation, Hooke’s law
 

Deformation is the changing of the shape of a body due to the forces and pressure applied on it. Strain is the force created by the elasticity of an object. Both deformation and strain are two very important concepts discussed under material science. These concepts are vital in the course of understanding subjects such as material science, mechanical engineering, civil engineering and even biological sciences. The contribution of deformation and strain to these sciences are enormous, and these concepts are vital to excel in these fields. In this article, we are going to discuss what deformation and strain are, their definitions, similarities of deformation and strain, and finally the differences between deformation and strain.

Strain

When an exterior stress is applied to a solid body, the body tends to pull itself apart. This causes the distance between atoms in the lattice to increase. Each atom tries to pull its neighbor as close as possible. This causes a force trying to resist the deformation. This force is known as strain. This effect can be explained using the potential energy of the bonds. The bonds inside a material act like small springs. The neutral position or the equilibrium position of the atom is when there is no force acting on the object. When a force is applied the bonds are stretched or contracted. This causes the potential energy of the bonds to get higher. The potential energy created by this in turn creates a force, which is opposite to the applied force. This force is known as the strain.

Deformation

Deformation is the change of the shape of any object due to the forces acting upon it. Deformation comes in two forms. They are namely elastic deformation and plastic deformation. If a graph of stress versus strain is plotted, the plot will be a linear one for some lower values of strain. This linear area is the zone in which the object is deformed elastically. Elastic deformation is always reversible. It is calculated using Hooke’s law. The Hooke’s law states that for the elastic range of the material, applied stress is equal to the product of the Young’s modulus and the strain of the material. The elastic deformation of a solid is a reversible process, when the applied stress is removed the solid returns to its original state. When the plot of stress versus strain is linear, the system is said to be in the elastic state. However, when the stress is high, the plot passes a small jump on the axes. This is the limit in which it becomes a plastic deformation. This limit is known as the yield strength of the material. Plastic deformation occurs mostly due to the sliding of two layers of the solid. This sliding process is not reversible. The plastic deformation is sometimes known as the irreversible deformation, but actually, some modes of plastic deformation are reversible.