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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
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