Stress - Strain Curve | Plastic Region

Added: 2026-05-22

[00:00:00]So, we have discussed the stress-strain curve of metals. Now, in this video, we are going to divide the stress-strain curve into two main parts.

[00:00:11]So, if you see here the stress-strain curve we can broadly divide into two main parts.

[00:00:23]Okay?

[00:00:24]From O to B and from B to A.

[00:00:28]So, the region from O to B, the stress-strain relationship, that is called as the elastic behavior region.

[00:00:35]And the point the region from B to A up to the fracture point that we can call the plastic behavior region.

[00:00:44]So, if you remember, elastic behavior is that which is reversible.

[00:00:49]So, in the elastic region, what happens?

[00:00:52]If stress is applied on the material the material undergoes deformation, elongation, and when the stress is removed, the load is removed, the material returns back to its original state.

[00:01:05]So, this is from O to B. That is the proportional region OA, the Hooke's law region, and then from A to B, where B is the elastic or yield point, which we have discussed.

[00:01:16]Now, beyond B, what happens is that here the stress-strain relationship is not proportional. So, here strain goes on increasing even when the applied stress is less. For a small amount of stress, the strain produced is very much. And another important thing other things come into play. Such as elastic hysteresis uh where there is always a residual strain, a permanent strain, which is produced. So, here, what happens is that in this region elastic hysteresis is there. It means there is always a permanent strain in the rod, and the material, the metallic material, it does not return back to its original shape and size. There is always some permanent strain in it, which is irreversible. So, this is plastic behavior. Then goes the tensile strength point, which is the maximum stress which the metallic material can withstand without disintegrating, without breaking or fracture. And then comes the point E, where finally the material undergoes uh deformation and breaks apart. So, plastic deformation is irreversible. It cannot be reversed.

[00:02:32]The metal material, after undergoing stress, it does not under return back to its original shape and size. There is always a permanent strain present in it.

[00:02:43]So, the two main categories, elastic behavior region and plastic behavior region, OB and BP.