Ductile mid brittle material:

A material that can undergo large permanent deformation in tension, that is, it can be drawn into wires is called as ductile. A material which can be slightly deformed without rupture is termed as brittle.

Ductility of material can be measured by percentage elongation of specimen or percentage reduction in cross sectional area of the specimen when failure occurs. If L is original length and L' is final length, then

% increase in length =     L' -L / L x 100

The length l can be measured by putting together 2 portions of the fractured specimen. Similarly if A is the original area of cross section and A is minimum cross sectional area at the fracture, then

% age reduction in area =    A - A' / A x 100

A brittle material such as cast iron or concrete has very little elongation and very little reduction in cross sectional area. A ductile material such as steel or aluminium has large reduction in area and increase in the elongation. An arbitrary % elongation of 5% is frequently taken as the dividing line between these 2 classes of material.