DEFINITIONS AND APPLICATION: Yield strength is the stress at which a material exhibits a specified limiting deviation from proportionality of stress to strain. The deviation is expressed in terms of strain which may be measured either by the Percent Offset method or by the Extension Under Load method as described in ASTM E8. The method of measurement must be stated when reporting yield strength. The term is applicable to materials whose stress-strain diagram in the area of transition from elastic to plastic strain is a smooth curve as well as to those which exhibit an upper yield point or sharp knee. Yield point is a special case of yield strength which is defined as the first stress in the material@ less than the maximum attainable stress@ at which an increase in strain occurs without an increase in stress. Since in their commercial form only ferrous metals exhibit this phenomenon and then only under some circumstances@ it follows that the term yield point has only limited application to the results of tensile testing of ferrous metals and is not applicable to the testing of nonferrous metals.
SAE J450-1984 history
2017SAE J450-2017 Use of Terms Yield Strength and Yield Point
2002SAE J450-2002 Use of Terms Yield Strength and Yield Point
1996SAE J450-1996 Use of Terms Yield Strength and Yield Point
1991SAE J450-1991 Use of Terms Yield Strength and Yield Point
1984SAE J450-1984 Use of Terms Yield Strength and Yield Point