yieldstrength

Yield strength, or yield stress, is a mechanical property that describes the onset of plastic deformation in a material under load. It marks the end of the elastic region on the stress-strain curve; below this stress, deformation is reversible.

Because many metals do not have a sharp yield point, the 0.2% offset yield strength is commonly used. It is defined as the stress at which the material has accumulated 0.2% plastic strain, as determined from a uniaxial tensile test.

The yield strength is distinct from tensile (or ultimate) strength, which is the maximum stress the material can sustain before fracture. In some steels, a yield point phenomenon produces an upper and lower yield point; after yielding, flow begins at a relatively constant stress.

Yield strength depends on temperature, strain rate, and the material’s microstructure, which can be altered by alloying and heat treatment. It can vary with direction in anisotropic materials and may change with prior work hardening.

In engineering design, yield strength serves as a criterion to ensure components remain in elastic service under expected loads. It is typically reported in MPa or ksi and is determined by standardized tensile tests such as ASTM E8/E8M.