Definition of yielding point in a stress–strain curve In a standard tension test on ductile materials, the stress level at which extension increases much more rapidly compared to the accompanying increase in load is called the:

Introduction / Context:
The stress–strain curve of ductile materials (such as mild steel) has characteristic regions: elastic, yield, strain hardening, and necking leading to fracture. Correctly naming these regions is vital for design, as service stresses are typically kept below the yield point with appropriate safety factors.

Given Data / Assumptions:

• Standard tensile test under quasi-static loading.
• Ductile material (e.g., low-carbon steel) showing a distinct yield phenomenon.
• Engineering stress–strain interpretation.

Concept / Approach:
At the onset of yielding, a small increase (or even a slight decrease) in load can produce a disproportionately large elongation. This marks the transition from purely elastic behavior (recoverable strains) to plastic behavior (permanent deformation). The corresponding stress level is the yielding point.

Step-by-Step Solution:
Load up to proportional limit → linear relation sigma = E * epsilon.Approach elastic limit → slight nonlinearity precedes yield.At yield → significant strain increase with little load change, defining the yield point.Beyond yield → plastic flow and strain hardening until ultimate stress, then necking to fracture.

Verification / Alternative check:
In mild steel, upper and lower yield points may appear; the lower yield point is commonly taken for design checks. For materials without a clear yield, a 0.2% proof stress is defined to represent the yield condition.

Why Other Options Are Wrong:
Elastic point refers to the purely elastic regime below yield. Plastic point is not a standard term for the onset of large inelastic strains. Breaking point is the fracture stress, far beyond yield.

Common Pitfalls:
Confusing yield with ultimate strength; ultimate tensile strength corresponds to the peak engineering stress and occurs after considerable plastic deformation.

Final Answer:
yielding point