Ductile, Ductile Fracture
Index
A ductile material is one that can be plastically deformed before it fractures.

Ductile fracture occurs when a material fails in the plastic deformation region of the stress-strain curve. In a polycrystalline material the fracture surface tends to show two distinct regions. At the sample axis, the mean fracture surface is normal to the tensile axis. As the fracture process comes to the sample surface the mean fracture surface makes an angle of 450 to the tensile axis, the direction in which the shear stress is maximum. The fracture surface has a "cup-cone" form, the cone being illustrated in the photograph of a low carbon steel.

From: Schaffer et al, "The Science and Design of Engineering Materials," 
Irwin (1995)