In a tensile test, the stress at which permanent deformation begins is called the yield point. Which of the following best describes this concept?

In a tensile test, the stress at which permanent deformation begins is called the yield point. Which of the following best describes this concept?

• A. The onset of plastic deformation
• B. Elastic deformation only
• C. Maximum elastic limit
• D. Point of fracture

Answer: (A)

The yield point marks the transition from elastic to plastic behavior in a tensile test. Up to this stress, the material elastically deforms and will return to its original shape when the load is removed. Beyond the yield stress, permanent, or plastic, deformation begins and the material does not fully recover after unloading. So the yield point is best described as the onset of plastic deformation. The other descriptions don’t fit: elastic deformation only refers to the portion before yielding, not the start of permanent change; “maximum elastic limit” is not the standard term for this boundary; and the fracture point is far beyond yielding, when the material finally breaks.

The yield point marks the transition from elastic to plastic behavior in a tensile test. Up to this stress, the material elastically deforms and will return to its original shape when the load is removed. Beyond the yield stress, permanent, or plastic, deformation begins and the material does not fully recover after unloading. So the yield point is best described as the onset of plastic deformation.

The other descriptions don’t fit: elastic deformation only refers to the portion before yielding, not the start of permanent change; “maximum elastic limit” is not the standard term for this boundary; and the fracture point is far beyond yielding, when the material finally breaks.