Mechanical properties of Material

Mechanical Properties Of Material

ByAvinash N. Fulbaria

CONTENTIntroductionHardnessCreepElasticityHardeningPlasticityReference

IntroductionThe substances which are useful in the field of engineering are

called Engineering materials. A particular material is selected is on the basis of following considerations

Properties of material Mechanical properties - strength, ductility, toughness,

hardness, strength to weight ratio etc. Physical properties - density, specific heat, thermal expansion, conductivity , melting point etc. Chemical properties - oxidation , corrosion, flammability,

toxicity etc. Manufacturing properties - formed, casting, machined, welding

HardnessHardness is the resistance of material to

permanent deformation of the surface.Hardness is not a fundamental property of a

material, but a combined effect of compressive, elastic and plastic properties

It can be measured by nondestructive testing.

increasing hardness

most plastics

brasses Al alloys

easy to machine steels file hard

cutting tools

nitrided steels diamond

Hardness MeasurementHardness measurement can be in Macro,

Micro & nano – scale.Measurement of the Macro-hardness of

materials is a quick and simple method of obtaining mechanical property data.

The Macro-hardness measurement will be highly variable.

Micro-hardness measurements are appropriate.

Hardness Measurement MethodsRockwell hardness testBrinell hardnessVickersKnoop hardnessshore

Hardness Testers

Creep When materials under severe service

conditions are required to sustain steady loads for long periods of time, they undergo a time dependent deformation.

the slow and progressive deformation of a material with time at constant stress.

Factors affecting creepLoad TemperatureCompositionGrain sizeHeat treatment

ElasticityThe property of a material to regain its

original configuration after removal of external forces.

Elasticity

HardeningThe heat treatment process in which we can

improve the hardness of the material is called hardening.

Hardening is a metallurgical and metalworking process used to increase the hardness of a metal.

Hardening process

PlasticityProperty of material to be deformed repeatedly

without rupture by the action of a force, and remain deformed after the force is removed.

Property of material due to material does to regain its original configuration that property is termed as Plasticity

Plastic Deformation (Metals)

15

1. Initial 2. Small load 3. Unload

Plastic means permanent.

F

linear elastic

linear elastic

plastic

planes still sheared

F

elastic + plastic

bonds stretch & planes shear

plastic

Plastic Deformation (permanent)From an atomic perspective, plastic deformation

corresponds to the breaking of bonds with original atom neighbors and then reforming bonds with new neighbors.

After removal of the stress, the large number of atoms that have relocated, do not return to original position.

Yield strength is a measure of resistance to plastic deformation.

ReferenceO.P. KHANNA , DHANPAT RAI PUBLICATIONS,

2013

END