Mechanical Properties Of Metals : Toughness, Elasticity, Plasticity, Brittleness
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Toughness

Toughness is the property that enables a material to withstand shock and to be deformed without rupturing .

Toughness may be considered as a combination of. strength and plasticity.

It is metal ability to absorb energy before fracture. Recall that ductility is a measure of how much something deforms plastically before fracture, but just because a material is ductile does not make it tough.

The ability of a metal to deform plastically and to absorb energy in the process before fracture is termed toughness.

The key to toughness is a good combination of strength and ductility. A material with high strength and high ductility will have more toughness than a material with low strength and high ductility.

Therefore, one way to measure toughness is by calculating the area under the stress strain curve from a tensile test. This value is simply called “material toughness” and it has units of energy per volume. Material toughness equates to a slow absorption of energy by the material.

Elasticity

When a material has a load applied to it, the load causes the material to deform. Elasticity is the ability of a material to return to its original shape after the load is removed. Theoretically, the elastic limit of a material is the limit to which a material can be loaded and still recover its original shape after the load is removed.

Plasticity

Plasticity is the ability of a material to deform permanently without breaking or rupturing.

This property is the opposite of strength. By careful alloying of metals, the combination of plasticity and strength is used to manufacture large structural members. For example, should a member of a bridge structure become over­loaded, plasticity allows the overloaded member to flow allowing the distribution of the load to other parts of the bridge structure.
Brittleness

Brittleness is the opposite of the property of plastic­ity.
A brittle metal is one that breaks or shatters before it deforms. White cast iron and glass are good examples of brittle material.

Generally, brittle metals are high in compressive strength but low in tensile strength. As an example, you would not choose cast iron for fabricating support beams in a bridge.
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