Strength of materials: the ratio of the maximum (largest) load reached in a tensile test to the original cross-sectional area is known as which stress?

Introduction / Context:
Tensile testing reveals the mechanical behavior of materials under uniaxial loading. The engineering stress–strain curve features several key points: proportional limit, yield point or proof stress, ultimate tensile strength, and fracture strength. Understanding these definitions is essential for safe mechanical design and material selection.

Given Data / Assumptions:

• Standard tensile specimen with known original cross-sectional area.
• Load is increased monotonically until fracture.
• Engineering stress is defined using the original area (not true stress).

Concept / Approach:
Ultimate tensile strength (often abbreviated UTS) is defined as the maximum load sustained by the specimen divided by the original cross-sectional area. Beyond this point, necking causes a reduction in load-bearing capacity even though local true stress in the neck may rise further; engineering UTS nevertheless corresponds to the peak load on the engineering curve.

Step-by-Step Solution:

Verification / Alternative check:
Comparison with yield stress (onset of plastic flow) and fracture stress (load at break) confirms UTS’s distinct definition as the curve’s peak load divided by A0.

Why Other Options Are Wrong:

• Yield point stress: corresponds to onset of plasticity, not the maximum load point.
• Breaking stress: based on the load at fracture, usually less than UTS in ductile metals.
• None of these: incorrect because “ultimate stress” matches precisely.

Common Pitfalls:
Confusing engineering and true stress; using reduced (necked) area in UTS calculation; misidentifying yield for materials without a clear yield point (use proof stress).

Final Answer:
Ultimate stress