Mechanical Properties of Materials

The behaviours of different materials under similar loading conditions are not the same. Each material is having its own properties depending on so many factors such as the natural properties of its ingredients, composition of ingredients (proportion), the structure and formation of grains, the manufacturing process etc. From engineering point of view, the important mechanical properties of materials are elasticity, plasticity, hardness, toughness, brittleness, ductility, malleability, creep and fatigue.

Elasticity:

Elasticity is the property of a materials due to which the whole of the deformation produced on it by an external load disappears completely on the instant of removal of the load disappears completely on the instant of removal of load. That is an elastic material regains its original shape and size as soon as the external loads are removed. No material is perfectly elastic. The limiting value of stress upto and within which the material is elastic is called the elastic limit of the material.

Plasticity:

Plasticity is the property by which a material shows a phenomenon of flow with comparatively less load. A material is said to be plastic when it can be easily moulded into any shape. The deformation produced by an external load on a plastic material will not disappear completely on the were removal of the load.

If a portion of total deformation produced by the external load disappears on the removal of load then that material is said to be elastic-plastic or semi-plastic. Most of the elastic materials enter into plastic stage before their failure.

Hardness:

The firmness or solidness of a material is called the hardness. Hardness is the property of any material by virtus of which it resists indentation or penetration of other bodies. Hard materials offer more resistance against abrasion and attrition. Hardness is somewhat related to the tensile strength of the material.

Toughness:

It is the property by virtus of which the material offers greater resistance against impact forces. A tough material absorbs more energy and hence it cannot to be broken easily by hammering.

Brittleness:

A material which breaks into pieces under a tensile load or impact is called a brittle material. This indicates the lack of ductility and malleability of the material. The elongation of a brittle material under tension before failure is practically negligible. Brittle materials do not enter into plastic stage before failure.

Ductility:

Capable of being drawn into thin wire is called ductile. Therefore ductility is the properly of any material by virtue of which it elongates more under tensile loads.

Malleability:

The property due to which a material can be pressed into thin plates is called malleability.

Creep:

A metal undergoes an instantaneous strain on the application of an external force. Such strain further increases with respect to time when the force is applied on the metal continuously for a long duration. Thus the time dependent component of the total strain is called “creep”.

Fatigue:

A metal which could safely resists a high value of uniform and static stress, sometimes, fails under a low value of fluctuating or reversing stress. This properly of a metal is called “fatigue”.