Question

In a typical stress-strain diagram for mild steel, the yield point is characterized by:

• A. A sudden drop in stress
• B. A linear relationship between stress and strain
• C. A plateau after the elastic limit is reached
• D. An immediate fracture following elastic deformation

Hint:

In mild steel, yield = flat stretch on the stress-strain curve. That’s the plateau where plastic flow starts!

Answer 1

The Correct Option is C

In a stress-strain diagram, the yield point is a key feature that marks the transition from elastic deformation to plastic deformation. Behavior in Mild Steel:

• Mild steel exhibits a clear and well-defined yield point.
• Just after the elastic limit is crossed, the material enters a region where strain increases with little to no increase in stress — this appears as a plateau on the diagram.
• This region is called the yield plateau and is unique to materials like mild steel.
• It consists of an upper yield point (initial drop) followed by a lower yield point where the stress remains nearly constant.

Why Other Options Are Incorrect:

• (A) Sudden drop in stress: This describes only the upper yield point, not the overall behavior.
• (B) Linear relationship: This applies only in the elastic region before yielding.
• (D) Immediate fracture: Fracture happens much later in the plastic region, not at yield.

Therefore, in mild steel, the yield point is best identified by the plateau following the elastic limit.