Yield (materials science)

Yield is the onset of permanent deformation in a material under applied stress. It marks the transition from predominantly elastic behavior to plastic deformation.

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Stress–strain curve: A graph showing a material’s deformation response as applied stress changes. Yield is identified on this curve where deformation stops being fully recoverable.
Stress (mechanics): Internal force per unit area transmitted through a material in response to loading. Yield is commonly specified as the stress at which permanent deformation begins.
Yield strength: The stress associated with the onset of significant plastic deformation in a material. It gives a numerical design value for the onset represented by yield.
Ultimate tensile strength: The maximum engineering tensile stress reached during a tensile test. It occurs after yield in ductile materials and measures a different limit.
Mild steel: A low-carbon steel used widely in structural and general engineering applications. Some mild steels exhibit distinct upper and lower yield points with Lüders bands.
Dislocation: A line defect in a crystal lattice that enables neighboring atomic planes to slip. Dislocation motion is the main microscopic mechanism of yielding in crystalline metals.
Strain: A dimensionless measure of deformation relative to an object's original dimensions. Yield criteria pair stress with the resulting strain to distinguish recoverable from permanent deformation.
0.2% offset method: A method that estimates yield strength by intersecting a stress–strain curve with a line offset by 0.2% strain. It supplies a repeatable yield value when no sharp yield point exists.
Fracture strength: The stress at which a material specimen breaks under specified loading conditions. Fracture ends load-bearing integrity, whereas yield marks permanent deformation without necessarily breaking.
Aluminum alloy: A metallic material in which aluminum is the principal constituent and other elements modify its properties. Many aluminum alloys show gradual yielding, making an offset definition useful.