Questions regarding the yield limit of stainless steel
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The strength at 0.2% deformation is generally taken as the yield strength of stainless steel. However, 1% is used in PED and some European standards. Where does this 1% come from, and under what circumstances is it applicable? What is the difference from 0.2%?
There are three commonly used yield criteria in engineering: (1) proportional limit, which is the highest stress at which a linear relationship exists on the stress-strain curve; it is commonly denoted by σp internationally, and the material is considered to have begun yielding once σp is exceeded. (2) Elastic limit: The highest stress at which a material can return to its original state completely elastically, based on the criterion that no residual permanent deformation occurs after the sample is loaded and then unloaded. Internationally, it is usually denoted by σel. The material is considered to begin yielding when the stress exceeds σel. (3) Yield strength is defined based on the occurrence of a specified amount of residual deformation; for example, the stress at 0.2% residual deformation is typically used as the yield strength, denoted by σ0.2 or σys. The poster is probably referring to %1 as the elastic limit, while what we define is the yield strength – the two are not the same