Welding Inspection & Metallurgy API ICP Self Study Notes

Elongation is the increase in gage length, measured after fracture of the
specimen within the gage length, usually expressed as a percentage of the
original gage length. A materials ductility, when subjected to increasing
tensile loads, can be helpful to the designer for determining the extent to
which a metal can be deformed without fracture in metal working operations
such as rolling and extrusion.