True Stress And Strain

Before going to the description of true stress and strain, first, we will discuss the definition of stress and strain. Stress is known for the external force applied per unit area. The unit of stress is  N/m2.

Strain is known for the deformation undergone by the object in the direction of force applied that leads to the change in the length of the body or object divided by the original length of the object. The strain has no unit as it is a dimensionless quantity.

The article also appropriately explains the types of true stress-strain and their effect on the materials. So, there will be clearance in the difference between two terms that are similar and slightly different. 

The relationship between stress and strain is explained briefly by the Hooke law described below in the article helps to understand stress and strain more effectively. And it also briefly explains the application and disadvantages of the law that applies only to inelastic materials.

What is true stress?

Force applied per unit area within elements that originate from externally applied forces, heat, etc.

Stress applied to the object is of two types.

1)Tensile stress

The tensile stress is the elongation of solid material or changes in the shape of object length in the direction of applied force, like stretching the object is a tensile force. It leads to an increase in length. The SI unit of tensile stress is Pascal.

Tensile stress helps the materials to show this property.

• Modulus of resilience
• Fracture stress
• Ultimate tensile stress
• Elastic modulus

2)Compressive stress

Compressive stress is the compression of elongated solid material in the direction of applied force. It leads to a decrease in length. The SI unit for compressive stress is the same as Pascal as the tensile stress.

There are three types of compressing the material by applying an external force.

• To elongate the material by applying the elongated force is the tensile stress.

• To compress the material by applying external force known as compressive stress.

• The equal forces outside and inside the application of the object across a cross-sectional area are known as shearing stress.

What is a strain?

Strain is known for the deformation undergone by the object in the direction of force applied that leads to the change in the length of the body or object divided by the original length of the object. 

Stress applied to the object is of two types.

1)Tensile strain 

The change in the object’s length by applying the tensile strain over it is known as tensile strain.

2)Compressive strain

The change in the length of the object by applying the compressive stress over it. 

True stress-strain formula

True stress= Force /Area per unit

Strain=Change in the length /original length.

True Stress-Strain curve 

Hooke’s law shows the relationship between stress and strain: The force applied to the material to stretch is proportional to the extension of the object or material.

Hooke’s law states that the strain of the material is directly proportional to the applied stress within the elastic limit of that material.

Hooke’s law is expressed in the formula as:

F = –k.x

Where 

F = force

x =Length Extension 

k =spring constant in N/m.

True stress-strain curve for mild steel

When mild steel undergoes a tensile force, it is under different stages before breaking. The true stress-strain curve of mild steel is the graphical representation of the stages undergone by mild steel.

Below are the stages undergone by the mild steel when hit by the tensile force.

• A proportional limit is when the ratio of stress and strain is constant.

• Elastic limit -In this limit, the mild steel will get its original shape after the tensile force is applied.

• Yield point -The limit at which mild steel cannot get its original shape.

• Ultimate stress point- The maximum stress point after the mild steel breaks.

• Breaking point -The point at which the mild steel breaks completely by the tensile force.

Conclusion

The article is all about true stress-strain in which the external force applied to the object changes the object’s deformation in a particular area. On the other hand, strain is changed in the object’s length by the stress at a specific strain of length is dimensionless. 

Here we have discussed the types of stress and strain, the true stress-strain formula, and what is the effect of stress and strain on the properties of the material. The relationship between stress and strain in the true stress-strain curve and true stress-strain curve of mild steel are described briefly in the article. Students can go through the above article and grasp a lot of ideas about true stress and strain in physics.