Yield Stress is defined as the stress at which a specific amount of strain (0.2%) occurs in the engineering tensile test.

• A. The stress at which a specific amount of strain (0.2%) occurs in the engineering tensile test.
• B. The maximum stress a material can withstand before fracture.
• C. The energy absorbed before fracture.
• D. The resistance to permanent deformation under load.

Answer: (A)

Yield stress is the stress at which permanent (plastic) deformation begins. On the engineering stress–strain curve, the material starts elastic, but for many metals there isn’t a sharp yield point. To have a clear, repeatable criterion, engineers use a 0.2% offset: draw a line parallel to the elastic portion of the curve, offset by 0.2% strain, and the stress where this line intersects the curve is the yield strength. This defines the stress corresponding to a small, fixed amount of plastic strain, making the value consistent for design.

The other options describe different properties: the maximum stress before fracture is the ultimate tensile strength; the energy absorbed before fracture is toughness; and while yield relates to resisting permanent deformation, the precise definition uses the 0.2% offset criterion rather than a general statement.