Yield stress is a measure of the strength of a material and is defined as the maximum stress a material can endure before it begins to permanently deform and is unable to return to its original dimensions. Yield stress is a material property and is the stress corresponding to the yield point at which the material begins to deform plastically). The yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior). Below the yield point, a material will deform elastically and will return to its original shape when the load is removed. Above the yield point, the material will deform plastically and will not return to its original shape when the load is removed).

The yield strength is often used to determine the maximum allowable load in a mechanical component, since it represents the upper limit to forces that can be applied without producing permanent deformation). Yield strength can be understood by looking at the stress-strain curve for a material. The mathematical formula for yield strength, or stress at yielding, is simply the basic formula for determining stress: force divided by area normal to the force. The yield strength is determined by creating a parallel, offset line at 0.2% positive strain from the linear portion of the stress-strain graph. The stress at the intersection point of the offset line and the stress-strain graph is the yield strength of the material.

Yield stress is an important factor in determining the mechanical properties of materials, and it is commonly used in metallurgy and physical metallurgy to test the mechanical properties of materials. Yielded structures have a lower stiffness, leading to increased deflections and decreased buckling strength). The structure will be permanently deformed when the load is removed, and may have residual stresses).