Difference Between Stress and Strain

Stress vs Strain

Stress and strain are physical properties of a material when it is put under pressure or load is applied to it. A solid, when it is put under pressure, has the ability to get deformed. The pressure per unit area of the solid is referred as stress while the deformity that takes place because of this stress is called the resulting strain. Strain and stress are intricately related with each other and strain results only because of stress. This article attempts to highlight the differences, as well as, the relation between stress and strain.

We all know that rocks are under constant pressure, but it is hard to imagine that a substance as hard as rocks can give way or bend and break. But once students grasp the concepts of stress and strain, they understand how rocks give way and result in the formation of newer rocks. Three words, all beginning with S, (stress, strain, and structure), and used in geology, are the source of confusion among geology students. It is true that stress and strain are used in common everyday English too, but here we are concerned with their meaning in structural engineering and geology only.

Just imagine being put under pressure. Won’t you feel stressed out? This is the way to remember the meaning of stress even in geology. Students are given Play-Doh to make imaginary rocks and then apply pressure (read stress) on them to see if they give way (there is strain) and the resulting structure. Though using putty or Play-Doh gives students an idea as to what happens when there is considerable stress (pressure per unit area) on the rocks, it has to be understood that deformities in rocks take place because of thousands of years of continuous stress.


What is the difference between Stress and Strain?

• Stress is pressure per unit area applied to a rock or solid.

• Strain is the deformity or change in dimension of the rock as a proportion of the original dimension thus being a dimensionless quantity.

• Strain in a body is directly proportion to the stress it is put under within its elastic limits.

• Both stress and strain are important properties of rocks that explain deformation in rocks and formation of new layers of rocks over a longtime scale.