‘Stress‘ and ‘Strain‘ are the most encountered terms when it comes to studying Elasticity. Though, it might not have such a huge weightage in competitive exams like JEE/NEET, but trust me ladies and gentlemen : “There’s no Mechanical Engineering without these 2 terms” – Being a student pursuing my UG degree in Mechanical, I can confirm this. And if there’s no Mechanical, there are no cars, bridges, buildings, etc.
Through this article, We are going to find out which one of the two comes first – is it Stress or is it Strain ?
Table of Content :
- Introduction to Stress
- Introduction to Strain
- Final Decision
1. Introduction to Stress :
Stress is defined as the Internal Restoring Force acting per unit area.
Now, What is this Internal Restoring Force ? Let’s understand the process to know what happens inside the material
The atoms inside the solid are arranged in a spring-ball system. So, when a load (external force) is applied, it disturbs the equilibrium state by making the springs deformed. This deformation is responsible for the Internal restoring force and we call it as Restoring, because it tends to bring the system back to its equilibrium.
The following flow-chart explains the process :
2. Introduction to Strain :
Strain is defined as ‘Change in Dimensions / Original Dimensions’
Again, there are types of strain :
- Longitudinal Strain – Change happens in the length
- Shear Strain – There is a shift which leads to an angle change
- Volumetric Strain – Change happens in the Volume
3. Final Decision
Now, It’s very much clear from the above discussion that : it’s the Strain which comes first ! All of this because of the Definition of Stress. Most of the times, we just memorize the formula of Stress as ‘Force/Area’ which is not complete.
- Complete Answer is : Stress = Restoring Force/Area
