Which of the following statements is false?

Asked in SSC JE 24/01/2018 (Morning)

Detailed Explanation

The tensile stress–strain curve of mild steel has some special features.

Why “None of these” Is Correct

It shows an upper and a lower yield point — 2 yield points. True.
After yielding, stress rises again to the ultimate value — strain hardening. True.
It stretches a lot (about 20–25%) before breaking — ductile. True.

None of the statements is false, so the answer is (d).

Stress–strain curve of mild steel in tension. O–A: straight line, Hooke's law holds up to the limit of proportionality A. B: elastic limit. C and D: upper and lower yield points. D–E: yielding at nearly constant stress. E–F: strain hardening up to the ultimate stress F. G: fracture.

Why the Other Options Are Wrong

A. Mild steel has 2 yield points: True: mild steel has upper and lower yield points.
B. Mild steel shows strain hardening: True: the curve rises after the yield plateau.
C. Mild steel is a ductile material: True: mild steel is ductile.

Key Point

Mild steel: upper/lower yield points, yield plateau, strain hardening, necking, ductile.

Key Concepts for Students

High-strength steels often have no clear yield point (0.2% proof stress used).
Percentage elongation measures ductility.
Mild steel has about 0.15–0.25% carbon.

Practice more: this is question 32 in Stress and Strain MCQs – Part 3. Try the whole set and check every answer instantly.