Elastic bodies regain their original shape due to internal restoring forces. This internal restoring force, acting per unit area of a deformed body, is called a stress.
An object can be deformed in different ways.
Here, the deforming forces act normally over an area of a body. The normal stress is subdivided into two categories:
If there is an increase in the length of the body in the direction of force applied, the stress set up, is called tensile stress.
If there is a decrease in length (decrease in volume) due to the force applied, the stress is compression stress
When the deforming force act tangential to the surface of the body, then this tangential force per unit area is called tangential stress (F). See diagram below.
