Which statement best describes yield strength?

Which statement best describes yield strength?

• A. The load limit to which steel will stretch
• B. The maximum load before complete failure
• C. The rate of elongation under load
• D. The ductility of the steel

Answer: (A)

Yield strength is the stress at which steel begins to deform plastically. Up to this point, the deformation is elastic and the material would return to its original shape if the load is removed. Beyond this point, permanent, or plastic, deformation occurs and the steel will have a permanent elongation. The statement describes the load limit at which steel will start to stretch beyond elastic behavior, which is exactly the boundary between elastic and plastic deformation. The other ideas refer to how much load the material can bear before it fully fails (ultimate strength), how fast it elongates under load (rate of elongation/strain), or how much total plastic deformation it can undergo before fracture (ductility), none of which capture the onset of plastic behavior that defines yield strength.

Yield strength is the stress at which steel begins to deform plastically. Up to this point, the deformation is elastic and the material would return to its original shape if the load is removed. Beyond this point, permanent, or plastic, deformation occurs and the steel will have a permanent elongation. The statement describes the load limit at which steel will start to stretch beyond elastic behavior, which is exactly the boundary between elastic and plastic deformation. The other ideas refer to how much load the material can bear before it fully fails (ultimate strength), how fast it elongates under load (rate of elongation/strain), or how much total plastic deformation it can undergo before fracture (ductility), none of which capture the onset of plastic behavior that defines yield strength.