PHYSICAL PROPERTIES OF MATERIALS.pdf(1).pdf

A physical property is any property that is measurable, whose value describes a state of a physical system.

1. PHYSICAL PROPERTIES OF MATERIALS
AA physical property is any property that is measurable, whos e value describes a
stateofaphysicalsystem.
AThe changes in the physical properties of a system can be used to describe its
changesbetweenmomentarystates.
APhysicalproperties areoftenreferred toas observation.
There
are
following
properties
of
the
materials
:
There
are
following
properties
of
the
materials
:
1.Density: pThedensityof a material is its mass per unit volume. Its unit is kg/m
3
. The
density of an element is determined by its atomic number and o ther factors, such
asatomic radiusandatomicpacking.
pThe density of a material is a function of temperature. The ge neral relationship is
thatdensitydecreaseswithincreasingtemperature.

2. Cont…
MATERIALS DENSITY (kg/m
3
)
Gold 19,300
Silver 10,500
Copper 8970
Aluminum 2700
Iron 7860
Steels 6920-9130
Lead 11350
Magnesium 1745
Ceramics 2300–5500
Glasses 2400–2700
Plastics 900–2000
Wood 400–700

3. 2. Melting Point: pFor a pure element, the melting point ( Tm) is the temperature at which the
material transforms from solid to liquid state.
pThe melting point of a metal depends on the energy required to separa te its
atoms.
pThe temperature range within which a component or s tructure is designed to
function is an important consideration in the selec tion of materials.
MATERIALS MELTING POINT (⁰⁰⁰⁰C)
Gold 1063 Silver
961
Silver
961
Copper 1082
Aluminum 660
Iron 1537
Steels 1371-1532
Lead 327
Magnesium 650
Ceramics -
Glasses 580-1540
Plastics 110-330
Wood
-

4. 3. Specific Heat: pA material’s specific heat is the energy required to raise the temperature of a unit
mass by 1 degree.
MATERIALS SPECIFIC HEAT (J/kg K)
Gold 129
Silver 712
Copper 385
Aluminum 900
Iron
460
Iron
460
Steels 500
Lead 130
Magnesium 1025
Ceramics 750-950
Glasses 500-850
Plastics 100-2000
Wood 2400-2800

5. 4.Thermal Conductivity: pThermal conductivity indicates the rate at which heat flows within and t hrough
a material.
pMetallically bonded materials (metals) generally ha ve high thermal conductivity,
while ionically or covalently bonded materials (cer amics and plastics) have poor
conductivity.
MATERIALS THERMAL CONDUCTIVITY (W/mK) Gold317
Silver429
Copper393
Aluminum
222
Aluminum
222
Iron74
Steels15-52
Lead35
Magnesium154
Ceramics10-17
Glasses0.6-1.7
Plastics0.1-0.4
Wood0.1-0.4

6. 5.Thermal Expansion: pThe thermal expansion of materials can have several significant effects,
particularly the relative expansion or contraction of different materials in
assemblies such as electronic and computer componen ts,glass-to-metal seals.
pThermal expansion in conjunction with thermal condu ctivity plays the most
significant role in causing thermal stresses (due to temperature gradients), both
in manufactured components and in tools and dies, a nd moulds for casting
operations.
6. Electrical, Magnetic, and Optical Properties:
•
Electrical conductivity
and the
dielectric
properties of materials are important
•
Electrical conductivity
and the
dielectric
properties of materials are important
not only in electrical equipment and machinery, but also in such manufacturing
processes as the magnetic-pulse forming of sheet me tals, resistance welding,
and the electrical-discharge machining and electroc hemical grinding of hard and
brittle materials.
•The units of electrical conductivity are mho/m or m ho/ft, where mho is the
reverse of ohm, the unit of electrical resistance.
•The influence of the type of atomic bonding on the electrical conductivity of
materials is the same as that for thermal conductiv ity.

7. Dielectric Strength
pAn electrically insulating material’s dielectric strength is the largest electric field
it can encounter without degrading or losing its in sulating properties.
pThis property is defined as the voltage required pe r unit distance for electrical
breakdown and has the units of V/m or V/ft.
Optical Properties
pAmong various other properties, colour and opacity are particularly relevant to
polymers and
glasses.
polymers and
glasses.
Piezoelectric Effect
pThe piezoelectric effect (piezo from Greek, meaning “to press”) is exhibited by
what are called smart materials.
pTwo basic behaviours are involved:
p(a) When subjected to an electric current, these ma terials undergo a reversible
change in shape.
p(b) when deformed by an external force, the materia ls emit a small electric
current.

8. pThis unique property is utilized in making transduc ers, which are devices that
convert the strain from an external force into elec trical energy. Piezoelectric
materials include quartz crystals and some ceramics and polymers,
pTypical applications are sensors, force or pressure transducers, inkjet printers,
strain gages, sonar detectors, and microphones.

9. Mechanical Properties of materials
1.Elasticity:
pThis is the ability of a material to deform under load and retu rn to its original
sizeandshapewhentheloadisremoved
2.Plasticity:
pThispropertyistheexactoppositeofelasticity.
pItisthestateofamaterialwhichhasbeenloadedbeyonditselasticstate.
pUnder a load beyond that required to cause elastic deformati on (the elastic limit)
a
material
possessing
the
property
of
plasticity
deforms
permanently
.
a
material
possessing
the
property
of
plasticity
deforms
permanently
.
pIttakesapermanentsetandwillnotrecoverwhentheloadisremoved
3.Ductility
pThis is the term used when plastic deformation occu rs as the result of applying a
tensile load. A ductile material combines the prope rties of a plasticity and
tenacity (tensile strength) so that it can be stret ched or drawn to shape and will
retain that shape when the deforming force is remov ed.
pFor example, in wire drawing the wire is reduced in diameter by drawing it
through a die.

11. 4. Brittleness
ABreaking of a material with little permanent distortion simply states the property
of brittleness.
ABrittle materials when subjected to tensile loads snap off wi thout giving any
significant elongation.
5.Tensile Strength
AStrength of the materials refers to the ability of a material to res ist the externally
applied forces without breaking or yielding.
6. Compressive strength
AThis is the ability of a material to withstand compressive (squeezing) loads
without being crushed or broken.
7
.
Shear
Strength
7
.
Shear
Strength
AThis is the ability of a material to withstand offset or transverse loads w ithout
rupture occurring.
AThe rivet connecting the two bars shown is in shear whilst the bars themselve s are
in tension.
ANote that the rivet would still be in shear if the bars were in compression
8. Hardness
AThis is the ability of a material to withstand scratching (ab rasion) or indentation
by another hardened body. It is an indication of the wear resistance of a material
.

12. 9. Toughness
AIt is the ability of a material to withstand bendin g without fracture due to high
impact loads. Toughness of material decreases when it is heated.
AIt is also measured by the amount of energy that a unit volume of the material
has absorbed after being stressed up to failure poi nt and is the area under stress
strain curve.
10. Resilience
AThe property of a material to absorb energy and to resist shock and impact loads
are known as resilience.
A
Generally, it is mentioned by the amount of energy absorbed per unit volume
A
Generally, it is mentioned by the amount of energy absorbed per unit volume within elastic limit.
11. Malleability
•It is the ability of materials to be rolled, flatte ned or hammered into thin sheets
without cracking by hot or cold working.
•Malleable material should be plastic but it is not essential to be strong and
malleability is considered as a compressive quality .
•Examples for malleability Al, Cu, Sn, Pb, soft stee l, wrought iron. This is the
property of a material to deform permanently under the application of a
compressive load.

13. 12. Creep
•When a part is subjected to a constant stress at hi gh temperature for a long
period of time, it will undergo a slow and permanen t deformation called creep
13.Machinability
•Machinabilityis defined as the “how much ease” a material can be machined
such as drill, lathe work, cutting etc.
14.Stiffness
AIt is the ability of a material to resist deformati on under stress.
A
Modulus of elasticity is the measure of stiffness.
A
Modulus of elasticity is the measure of stiffness.
AMaterial which suffers slight deformation under loa d has a high degree of
stiffness or rigidity. Steel beam is stiffer or mor e rigid than aluminium beam.

14. Composite
•A composite material is a material consists of two or more different material
which are different in chemical composition, insolu ble in each other and
macroscopically distinct, which are combined togeth er give enhanced
properties as compare to each individual material.
•
+
=
MATRIX
REINFORCEMENT
COMPOSITE
•
+
=
Role of matrix:
1. Binds fibres together.
2. Support the overall structure.
3. Protects the composite from humidity, chemicals, etc.
4. Protects fibres from damage due to handling
Role of reinforcement:
1. Strengthening
2. Carry load.

15. CLASSIFICATION OF COMPOSITES

16. Advantages of composite material
1. Taylor made properties
2. High strength to weight ratio
3. Good mechanical, thermal, electrical and chemical properties.
4. Low cost
5. Easily handling.