· The "toughness" of a material is measured by the area under the stress/strain curve to fracture. Toughness = ₀ / ^εσdε = Work per unit volume.
· The behavior of three different materials is illustrated: 
* A - a high strength material that fractures in the elastic range. 
* B - a high ductility material with a low yield stress; 
* C - a material with intermediate yield stress and ductility. 
· C is the Toughest of the group.