Stress–Strain Curve — Correct Sequence of Key Points Which of the following lists the proper chronological sequence of characteristic points as load increases in a ductile material under a standard tensile test?

Introduction:
Understanding the order of key points on the stress–strain curve is essential for material selection and design safety.

Given Data / Assumptions:

• Ductile metal specimen; standard tension test.
• Nominal engineering stress–strain curve.

Concept / Approach:
As load increases: linearity holds up to proportional limit; elastic behavior (recoverable strain) continues up to the elastic limit; yielding starts thereafter; ultimate and finally failure occur later. The listed options stop at failure initiation.

Step-by-Step Solution:
Proportional limit → end of strictly linear stress–strain relation.Elastic limit → largest stress with fully recoverable strain on unloading.Yielding → significant plastic strain starts (upper/lower yield in mild steel).Failure → fracture of the specimen.

Verification / Alternative check:
Reference curves in materials texts consistently show this order for ductile metals.

Why Other Options Are Wrong:

• Option B and C place limits out of order.
• Option D is incorrect because A matches standard definitions.

Common Pitfalls:
Confusing elastic limit with proportional limit; they are close but not identical.

Final Answer:
proportional limit, elastic limit, yielding, failure