Important mechanical properties of materials:-

ELASTICITY:- 

In this property body regains completely its original shape & size then it is called perfectly elastic body.

Elastic limit marks the partial break down of elasticity beyond which removal of load result in degree of permanent deformation.

Steel, aluminium, copper, may be considered to be perfectly elastic within certain limit

 

·    Plasticity:-

The characteristics of material by which it undergoes inelastic strain beyond those at the elastic limit is known as plasticity.

 This property is particularly useful in operation of pressing and forging.

When large deformation occurs in a ductile material loaded in plastic region, the material is said to undergo plastic flow.

Ductility:-

It is the property of material in which a material can be drown out longitudinally to a reduced section, under the action of tensile force.

 A ductile material must possess a high degree of plasticity and strength.

Ductile materials must have low degree of elasticity.

This is useful in wire drawing.

·   Brittleness:-

In brittle failure placed under without significant deformation

 Ordinary Glass is nearly ideal /brittle material.

Cast iron, concrete and ceramic are brittle material.

Malleability:-

It is the property of a material which permits to be extended in all direction without rapture.

A malleable material possess a high degree f plasticity, but not necessarily great strength.

·   Toughness:-

Toughness is defined as the amount of energy absorbed by material before it's fracture.

·   Hardness:-

It is the ability of a material to resist indentation or surface abrasion.

·   Strength:-

This property enables material to resist fracture under load.

This is the most important property from design point of view. Load required to cause fracture, divided by area of test specimen, is termed as ultimate. 

·   Creep:-

Creep is a permanent deformation which is recorded with passage of time at constant loading. It is plastic deformation (permanent and non-recoverable) in nature

·    The temperature at which creep is uncountable is called Homologous temperature.

·   Fatigue

Due cyclic or reverse cycle loading fracture failure may occur f total accumulated strain energy exceeds the toughness. Fatigue causes rough fracture surface even in ductile metals.

·   Resilience:-

It is the total elastic energy which can be stored in given volume of metal and can be released after unloading.

It is equal to area under load deflection curve within elastic limit.