Lecture No.1 - Introduction to Material Science
Transcript of Lecture No.1 - Introduction to Material Science
Chap No.:-1Introduction to Engineering Materials
By H . F. AdmarLecturer –Mechanical Engineering
Material
Material Everything than can be seen, touched or used.
Engineering Material Solid material or stuff out of which product can be made which is
useful in engineering profession.
Material Science It is the branch of applied science which deals with engineering
material and investigate the relation ship between structure of material and their properties for practical usefulness.
Classification Of Engineering Material Metals
A) FerrousB) Non-Ferrous
Ceramics
Organics
Need Of Material Science knowledge
Constant challenge of ever increasing demand of material with good characteristics.
Requirement due to new application.
Challenge of decreasing production cost to stay ahead in market.
Properties of Engineering Material
Material PropertyQualitative or Quantative measure or response of material
to externally imposed condition like force and temperature.
Types of Properties Physical---------- Chemical----------- Mechanical--------- Electrical------------ Thermal------------- Magnetic------------ Optical--------------- Technological-------
Properties of Engineering MaterialMaterial Property
Qualitative or Quantative measure or response of material to externally imposed condition like force and temperature.
Types of Properties Physical---------- - Dimension, density, porosity Chemical----------- Composition, corrosion resistance etc. Mechanical---------Elasticity, tensile strength, hardness, toughness
etc. Electrical------------Resistivity, superconductivity etc. Thermal------------- Heat capacity, thermal conductivity etc. Magnetic------------ Permeability, hysteresis Optical---------------Refractive index, Reflectivity, Absoptivity Technological------- Cast ability, Weldbility, solder ability etc
Definition of Metal PropertyPorosity It is the ratio of total pore volume divided by Bulk Volume.
Porosity = Total Pore Volume/ Bulk Volume
CompositionPercentage of various elements which make up metals and
alloys.
StructureIt refers to the microstructure of a material.
Contd.Corrosion ResistanceIt is the deterioration of material by chemical reaction with
its environment.
Stress It is internal resistance set up in a material to deformation
due to externally applied force.
Stress = Load/AreaUnit = ?
ElasticityIt is the ability of material to regain its original shape and
size after removal of load.
PlasticityIt is the ability of material to be permanently deformed
without fracture even after removal of external load.
StrengthIt is the ability of material to withstand stress without
fracture called as strength.
Material has to withstand different types of load i.e. tensile, compressive, shear etc.
StiffnessThe property of material which enables it to resist the elastic
deformation
Material which undergo less deformation has high degree of stiffness.
Ex. Steel beam and aluminum beam.
DuctilityIt is the property of material to undergo deformation under
application of tensile load without fracture.
It is measured in terms of Percentage Elongation/ Percentage reduction of area.
% Elongation = Lf-Lo/Lo * 100 Where Lf = Final Length
Lo= Initial Length
Defination.Malleability It is the capability of material to withstand deformation under
compression without rupture.
Gold is most malleable material.
Brittleness The property of material by virtue of which it will fracture
without appreciable deformation.
It is exactly opposite to ductile.
Material with 5 % elongation are considered to brittle.
Ex. Cast Iron, Concrete, Glass
Hardness It is the ability of material to withstand scratching, wear,
abrasion or indention by harder bodies is known as hardness.
Measured by Penetration Method.
Brinell, Rockwell and Vickers hardness test.
Toughness It is the amount of energy material can absorb before it
fractures.
This property indicate material strength when sudden load is applied.
ResilienceIt is the capacity of material to absorb/store energy and to
resist shock and impact. When stress is applied to body, how much energy it can
store will indicate its resilience capability.
Important for making spring.
Fatigue The failure of material under application of repeated load
or stress is known as fatigue.
Ex. Leaf spring used in automobile, Piston road in IC Engine, Pump and compressor.
CreepSlow and Progressive deformation of a material with time due
to constant stress is known as Creep.
Material subjected to high temperature and constant tensile stress will undergo such deformation.
Ex. Parts of IC Engine.
Electrical PropertyResistivityIt is the property which enable material to impedes or resist
flow of electricity through it.ρ = R.A/l
Where ρ = Resistivity ( in Ohm-cm)R = Resistance in Ω
A = C/s of the conductor in cm2
l = Length of the conductor in cm
Ex. Important property as Long distance transmission line require low resistive material.
ConductivityIt is the reciprocal of resistivity.
α = 1/ρ This property gives idea how easily material allow
electrical current to flow through it.
Ex. Rubber & Steel. Compare ?
Di-electric strength (Breakdown voltage)
It is the property which indicate capability of material to store electrical energy.
OR
Dielectric strength will also indicate minimum voltage which will result in destruction of insulating property
Every electrical apparatus is designed to operate between certain range of voltage beyond which it fails and storage property disappear.
Semi ConductivityConductivity between that of conductor and insulators is
called as semi conductivity.
Material which is semi conductor is neither a conductor nor a insulator.
Ex. Silicon, Germanium, Galena
Super ConductivityMaterial which exhibit zero resistivity and undetectable
magnetic permeability when cooled below absolute zero temperature ( -273* C) is known as super conductive material.
Best material for long distance power transmission line.
Thermal PropertyHeat CapacityIt is the property that indicate material’s ability to absorb
heat from external surroundings.
orIt is amount of energy required to produce a nit temperature
rise.
Mathematically,Heat Capacity C = dQ/ dT
Specific HeatIt is the amount of energy require to raise the temperature of
unit mass by unit degree.
Q= m *Cp *dT or m* Cv*dT
Where Cp = Specific Heat at Const. Pressure
Cv = Specific Heat at Const. Volume
Thermal ConductivityIt is the amount of heat conducted per unit time per unit c/s
area in the direction conduction when temperature gradient across the heat conducting element is one unit.
Unit of conductivity is ?
Thermal ExpansionExpansion of material under application of
thermal energy.
Co-efficient of thermal Expansion Amount of expansion in unit length of a solid material as a
result of a temperature rise of one degree.
Magnetic PropertiesPermeabilityIt is the ratio of magnetic flux and magnetic field strength.
µ = B/H Where B= Magnetic Flux
H= Magnetic field strength
HysteresisLag in the changes of magnetization behind variation of the
magnetic field.
For the same value of input during increasing and decreasing trend, there will be difference in the output value known as Hysteresis loop.
Optical PropertyReflective IndexIt is the ratio of velocity of light in vaccum to the velocity of
light within material Vm.
n = Vv/Vm
orIt is the ratio of sine of the angle of incidence I and sine of
the angle of refraction r.
n = sin t/sin r
Absoptivity Total energy fall on material , partially transmitted,
reflected and absorbed.T+R+A = 1
where T = Energy Transmitted R= Energy Reflected A= Energy Absorbed.
Technological PropertiesCast abilityIt is the ease with which the material can be given various
solid shapes from liquid state.
Factor which effect the cast ability are solidification rate, shrinkage, segregation, gas porosity, hot strength etc.
Machine abilityIt is defined as the ease with which a given material can be
cut or removed by cutting tools in machining operation with satisfactory finish at lowest cost.