Malleability vs. Brittlenes vs. Ductility
Malleability
- whereby a material can be plastic deformed and shaped when cold
A malleable material can be plastic shaped with hammering or rolling without fracture.
Typical malleable materials:
- mild steel, gold, lead
Brittleness
- whereby a material will fracture without appreciable prior plastic deformation
Brittleness is lack of ductility and for a brittle material there is no plastic deformation. The elastic stage is followed by immediate fracture.
Typical brittle materials:
- glass, concrete, ceramics, stone, gray cast iron
Ductility
- whereby a material can be plastic deformed by elongation without fracture
Ductile materials can typically be plastic elongated with more than 15% before they fracture.
Typical ductile materials:
- copper, mild steel, thermoplastics
Specification of Ductility
Ductility can be specified as percent elongation before rupture as
DL = 100% (Lf - L0) / L0 (1)
where
DL = ductility related to elongation (%)
Lf = final length of specimen at fracture (m, mm, in...)
L0 = original length of specimen (m, mm, in...)
Alternatively ductility can be specified as percent reduction of area as
DA = 100% (A0 - Af) / A0 (2)
where
DA = ductility related to reduction of area (%)
Af = final area of specimen at fracture (m, mm, in...)
A0 = original area of specimen (m, mm, in...)
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