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Mechanical Properties of Materials


IMPORTANT MECHANICAL PROPERTIES

The following are the most important are mechanical properties of engineering materials
1-     Elasticity
2-     Plasticity
3-     Ductility
4-     Brittleness
5-     Malleability
6-     Toughness
7-     Hardness

ELASTICITY
When external forces applied in the body, made of engineering materials, the external forces tend to deform the body while the molecular forces acting between the molecules offer resistance against deformation.  If the forces are gradually diminished, the body will return to its original shape.
Elasticity is the property by virtue of which a material deformed under the load and return to its original shape when load is removed. 

PLASTICITY
Plasticity is the converse of elasticity. A material in plastic state is permanently deformed by the application of load, and it has no tendency to recover. Every elastic material possesses the property of plasticity.
The characteristic of material by which it undergoes inelastic strains beyond those at the elastic limit is known as plasticity.

DUCTILITY
Ductility is the characteristics which permits a material to be drawn out longitudinally to a reduced section, under the action of tensile force.    
Ductile extension, a material shows a certain degree of elasticity, together with a considerable degree of plasticity. Ductility is measured in the tensile test of specimen of the material, either in terms of percentage elongation or in terms of percentage reduction in the cross-sectional area of the test specimen. The property of ductile is utilized in wire drawing. 
BRITTLENESS 
Brittleness implies lack of ductility.
A material is said to be brittle when it cannot be drawn out by tension to smaller section. 
In brittle material failure takes place under load without significant warning and the property is generally highly undesirable.
Examples of Brittle Material -: cast iron, high carbon steel, concrete,ceramics etc.

 MALLEABILITY
Malleability is a property of a material which permits the material to be extended in all directions without rupture. 
A malleable material possesses a high degree of plasticity, but not necessarily great strength.

 TOUGHNESS
Toughness is the property of material which enables to absorb energy without fracture.
This property is very desirable in components subject to cyclic or shock loading.Toughness is measured in terms of energy required per unit volume of the material, to cause the rapture under the action of gradually increasing tensile load.

 HARDNESS
Hardness is the ability of material to resist indentation or surface abrasion.
Tests on hardness can be classified into
1. Scratch test
2. Indentation test
The scratch test consist of pressing a loaded diamond into the surface of specimen, and then pulling the diamond so as to make a scratch.The indentation test consist of pressing a body of standard shape into the surface of the test specimen.




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