Ductility is defined as the ability of a material to deform plastically in tension or shear before fracture. Its measurement is of interest to those conducting metal forming processes (ex. automobile body panels); to designers of machines and structures; and to those responsible for assessing the quality of a material as it is being produced. Two measures of ductility are Elongation and Reduction of Area. Elongation is defined as the increase in the gage length of a test piece divided by the original gage length. Reduction of Area is defined as the decrease in the cross sectional area divided by the original cross sectional area. The conventional means by which these ductility measures are obtained is by pulling a specimen in tension until fracture.
ASTM E8 governs the determination of Ductility measures for Metals.