Materials, Properties and Design

· At the yield point the slope of the engineering stress-strain curve decreases and the applied stress reaches a maximum value at the Ultimate Tensile Strength (UTS) of the sample. An aluminum sample is shown.
· As deformation is continued past the UTS, the stress decreases and deformation is localized in a neck region until the sample fails by ductile fracture.
· The strain at fracture is a measure of the sample ductility.

From: Callister,
"Materials Science and Engineering,"
Wiley (1997)