#STRESS CONSEPT PART-2

 #Yield Strength, Sy

The point at which the specimen generates a large deformation without the addition of any load is called the yield point.

            Corresponding stress is called yield stress or yield Strength.

The point is easy to recognize for materials with a stress strain curve for figure (1)

 

 For figure (2), there is no apparent yield point 

 For this type of material common approach is amount of stress require to produce a fix amount of permanent deformation.

            Offset method of determining the yield point. ASTM signifies an offset strain of 0.2% to be used for common pipe material covered by it's specifications.