On this earth there are many materials available and each posses its own properties like Physical properties , chemical Properties and mechanical properties.

Mechanical properties are those which describe the behavior of material under different forces. properties like ductility , elasticity ,plasticity, brittleness, resilience , toughness , hardness , hardenability , strength , tensile/compressive strength  , fatigue strength.. Although these terms seem similar, there are some small key differences.

Before going to understand these topics , you must have to idea on stress, strain , strain-curve

Ductility

It is the property of materials to deform into long thin wires without undergoing fracture .

Elasticity 

This is the property of material to regain its original shape when external force is removed from it.

Plasticity 

The property of material to undergo permanent deformation . The body don’t regain its original shape even the external load is removed.

Brittleness

The property of material to get fracture without undergoing any elongation or contraction . Materials like Glass , most ceramics(Bricks, tiles ) are good examples of brittle materials.

Toughness

 Toughness is the ability of material to absorb energy and plastically deform without undergoing fracture . Toughness contains both strength and ductile properties. 

High strength material exhibits high resistance to force up-to some extent , after it will get fracture rather than elongating.

High ductile materials can get deformation easily , but they will elongate longer without getting fracture. 

So, Tough materials exhibit high strength up-to elastic limit , also these exhibit high resistance to fracture after deformation

Resilience is the ability of a material to absorb energy and return to its original shape without permanent deformation. It is a measure of the material’s toughness

Hardness 

Hardness is the resistance of a material to localized surface deformation, such as a cuts or scratch. It is not the same as strength; a material can be very hard but not necessarily strong. 

It is influenced by the strength of the interatomic bonds in the material. A hard material has strong interatomic bonds that make it difficult for indenters to penetrate the surface.

Hardenability

It is a measure of how much of a material can be hardened through heat treatment. It is influenced by the composition and microstructure of the material. Materials with high hardenability can be hardened to a greater depth than materials with low hardenability.

Tensile strength 

The maximum amount of tensile(pulling) stress at which a material can withstand without fracture.

Compressive Strength

The maximum compressive (pushing) stress a material can withstand without failure.

Fatigue strength 

It is ability of material to withstand cyclic loads ( loading and unloading continuously) without failure. It is important because , suppose a material can withstand at stress say 250 MPa , but this stress limit (tensile strength ). This strength will decrease as usage cycles increase . As we use the material ( no of cycles increases) the tensile strength will decrease .