 # Difference Between Stress and Strain

To understand solid mechanics ineffective way we should have knowledge about Forces and energies.  When we apply any force on any object. There are some changes in that object. These changes are known as stress and strain. When we apply a force on the body resisting force developed in the body. If we count that force as per unit area is known as stress. When there is a change in the dimensions of the object is known as strain. In this article, we will discuss in detail the difference between stress and strain. Both of these terms are very useful to understand the mechanics and the strength of the material which are very important for the students.

## Stress vs strain

 Sr.no Stress Strain 1. It is a resisting force per unit area of the object. After the application of external forces. Strain is the deformation per unit of the body after the stress application on the body. 2. Stress is the ratio between applied or resisting forces to the cross-sectional area of the object. It is the ratio between the change in the dimensions of the objects which is developed after the stress on the object to the original area of the object. 3 It is denoted by ‘σ’ sigma. Strain is denoted by ‘e’ 4 Mathematically formula for the stress is   σ=F/A Mathematically representation of strain is   e=dl/l 5 Its units are N/mm2 and N/m2. Strain is unitless. 6 It can exist without strain. It can’t exist without stress. 7 Tensile stress, compressive stress, shear stress are its types. Tensile strain, compressive strain, volume strain, and volumetric strain are its types.

## Stress

Stress is the ratio between the applied force resisting force of the body to the cross-sectional area of the object. It is also defined as resisting force per unit area.

Mathematically it can be expressed as:

σ = F/A

Where σ is stress and F is force and A is area.

SI unit of stress is Newton per meter square which is also known as Pascal Pa

### Types of stress

#### Tensile stress

When the developed stress in the body change is the length of the body d is known as tensile stress.

#### Compressional stress

When the developed stress by an external force changes the volume of the body is known as compressional stress.

#### Shear stress

In case when developed stress causes changes in the shape of the body that stress is known as shear stress. If the force acts parallel to the surface of a particular body, it exerts shear stress.

## Strain

It is the ratio change in the dimensional of the body when applied external force to the original dimension of the body. It is also known as the deformation per unit area. Deformation in one-dimensional strain in the body is the fractional change in the length of the body. It can be e represented mathematically as

e= dl/l

e is strain and dl is changing in length and l is the original length.

Strain is unitless

### Types of strain

#### Tensile strain

In case when straining in an object due to tensile stress. That strain is known as tensile strain.

Mathematically it can be represented as

e= dl/l

e is strain and dl is a change in length and l is the original length.

#### Compressive strain

When strain is developed in objects due to compressional stress. That strain is known as compressive strain.

#### Volumetric strain

If applied stress change is the volume of the object. In that case change, volume per unit volume is known as volumetric strain.

Mathematically it can be represented as

Volumetric strain = dV/V  .

#### Shear strain

When the alternate faces of a solid cube are subjected to shear stress. The developed strain is known as the shear strain.

Mathematically it can be represented as

Shear strain =da/a =tanϴ ## The key difference between stress and strain.

1. Stress is a resisting force per unit area that develops after the implementation of the external forces. While deformation per unit area of the object after the stress applied on the object.
2. Stress Is the ratio of the resisting force which develops after the application of the external forces to the cross-sectional area of the object. On the other hand, strain is the ratio of change in the dimensions of the object after the stress to the original area of the object.
3. Stress is represented by the symbol σ. and strain is represented by the symbol e.
4. SI unit of the stress is newton per meter square N/m2 or N/mm2 which is also equal to PA. while a strain is unitless.
5. Mathematically formula representation of stress is σ=F/A. and strain is represented by the formula e=dl/l.
6. Stress is possible without strain but the strain is not possible without the existence of stress.

## Conclusion

Stress is related to the applied force and strain is directly related to the stress. If stress is developed in objects after that there is the possibility of strain. To understand machines and the strength of material effectively these both terms are very important. Both these terms are very important in the designing of big machines.

For example, big turbines and are used in hydroelectric projects. In that case, every part is designed as per these terms.in hydroelectric projects, high water pressures have to befall on the turbines. To handle this large pressure all the parts should be designed with high accuracy. For higher accuracy, a good knowledge of stress and strain is needed. With the help of this article, you will be able to understand the basic concept of stress and strain.