Stress-strain graph for ductile material

Stress-strain graph for ductile material

Stress-strain diagram for ductile material

Here in this diagram on the y-axis stress and x-axis stress.

1. O to A

OA is an inclined line. O to A is called as a proportion limit. It means if we go on increasing stress, the strain will also increase.

The relation is directly proportional.

σ ∝ e

σ = Ee

Where E is "young's modulus" or "modulus of elasticity".

Now when we removed the load from point A. It stress become O. So I remove the load, this object return back to it's the original shape. It means it behaves in an elastic manner. So within this O to A region, the material behaves in an elastic manner. That is when the load is removed it will regain its original shape.

2. A to B

It is called an elastic limit. From A to B relation it is curved. The relation is not Linear but even if removing load at point B material should regain its original shape. So from A to B is an elastic limit. 

σeL ∝ eeL

3. B to C

When we from B to C the change in stress is not very much.

Point C is called "upper yield point". At point yielding is started ( yielding means changing in shape).

Once material crosses point B, It reaches in the region between B to C where It will be permanently deform. If we remove the load from point C then material would not regain it original shape. It means at point C it had deform permanently. So B to C region called as a per cent set.

4. C to D

Compare to point C point D is below, it means the stress at point D is less compare to point C but material deforming more. At point C strain is less and at point D strain is more but stress value is less.

Point D is called " lower yield point". Strain is more at point D than point C.

5. D to E

Point E is highest point in this graph so at point E we are getting maximum stress.

Point E is called "yield point". Stress is maximum at yield point.

6. E to F

From point E to F stress decrease but strain increase.

At point F material breaks. Hence It is called as breaking point.

If material having maximum stress after that it can break any given point.