TEF03
Lecture 2
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MATERIAL SCIENCE
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Oil barge brittlely fractured
CLASSIFICATION OF
ENGINEERING
MATERIALS
PROPERTIES OF
ENGINEERING
MATERIALS
Classification of engineering
materials
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materials are
classified to make it
is easier for
engineers to
remember and
make correct
choices on the best
material to use.
Popular Classifications
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elements, compounds and mixtures;
metal and non-metals;
raw materials and manufactured
materials;
organic, biological and inorganic; and
metals, polymers, ceramics and
biological.
Properties of engineering
materials
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Mechanical Properties
Physical Properties
Thermal Properties
Electrical Properties
Chemical Properties
Optical Properties
Mechanical Properties
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Malleability
Ductility
Hardness
Brittleness
Toughness
Elasticity
Plasticity
Stiffness
al metal for jewelry.
Mechanical Properties

Gold's malleable and soft
nature makes it an ideal
metal for jewelry.
Malleability – ability
of a material to be
plastically deformed by
hammering or filling
into sheet form. Eg.
Gold.
Mechanical Properties

Ductility – ability of a
material to be plastically
(permanently) deformed
by tension before
fracture occurs. Eg. Wire
drawing. Eg. Copper
wire.
Mechanical Properties
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Hardness – ability of a
material to resist
scratching or penetration.
Eg. Diamond & Glass
Mechanical Properties
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Texas glass skyscraper
Brittleness – tendency to
fracture without
appreciable deformation
particularly under low
stress. Eg. Diamond &
Glass
Mechanical Properties
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Fatigue – the
failure of a material
under the action of
repeated alternating
stresses. Eg.
Aluminium wire
Hawaiian flight Aloha 243 - a huge piece torn off the top part of the
fuselage leaving passengers exposed to the outside atmosphere at full
flight altitude. The incident was caused by metal fatigue. Metal fatigue is
caused from multiple depressurizations and the constant change in
temperature between cruising at altitude and being on the ground.
Mechanical Properties

Toughness –
materials ability to
withstand stresses
as well as
deformations.
Can withstand
impact load.
Mechanical Properties
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Elasticity – materials
ability to return to its
original shape after
being subjected to a
load that caused
deformation. Eg.
Elastic band, hunting
bow,
Mechanical Properties

Plasticity – the
ability of a solid
material to undergo
some degree of
permanent
deformation
without rupture.
Eg. Hot working a
metal, plaster sine
Mechanical Properties
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Stiffness – a
measure of a
materials ability to
resist deformation
or deflection under
load. Eg. Bridge
structure
A combination of a freak wave and excess material stiffness is blamed
for the near loss of the BT Imoca 60 in last year’s Transat Jacques Vabre
race.
Importance of Mechanical
Properties of Materials in
Engineering
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The need to acquire knowledge of the
properties of materials is ultimately for one
reason:
The correct selection of
a material for a given
application.
Physical Properties
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Density
Specific Gravity
Porosity
Moisture Content (MC)
Physical Properties
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Density
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Density is a measure of mass per unit of
volume
Physical Properties
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Specific gravity
Specific gravity is the ratio of the
density of that substance to the
density of water. This means that
specific gravity of water is equal to
1.
The main body of the raft was composed of nine balsa tree trunks up to 13.7
metres long, 60 cm in diameter, lashed together with 3.175 cm hemp ropes.
Cross-pieces of balsa logs 5.5 m long and 30 cm in diameter were lashed across
the logs at 1 m intervals to give lateral support.
Physical Properties
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Porosity
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the amount of voids or pores
present in the material
Apparent Porosity is the
measure by the amount of
water that can be absorbed
by the material.
True Porosity include those
voids sealed off from the
outside surface.
Here is an example of ring porous wood in which pores are arranged in concentric circles.
Physical Properties
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Moisture Content
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quantity of moisture a
material contains
Thermal Properties
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Heat
Boiling Point
Melting Point
Thermal Expansion
Thermal Conductivity
Thermal Properties
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Heat
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Russian wildfires leave 28 dead,
thousands homeless
Heat is a form of
energy associated
with the motion of
atoms, molecules and
other particles which
comprises of matter
Thermal Properties
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Boiling Point
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Boiling point of a
substance is the
temperature at which it
can change its state from
a liquid to a gas
throughout the bulk of
the liquid at a given
pressure.
Thermal Properties
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Melting Point
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Melting point of a crystalline
solid is the temperature at
which it changes state from
solid to liquid. When
considered as the
temperature of the reverse
change from liquid to solid, it
is referred to as the freezing
point.
Thermal Properties
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Thermal expansion
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Thermal expansion is the
tendency of matter to
increase in volume or
pressure when heated. It is
the distance which one unit
of length of a material
would expand if the
temperature were raised by
one temperature interval.
Thermal Properties
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Thermal Conductivity
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Thermal conductivity is the
intensive property of a
material that indicates its
ability to conduct or transfer
heat.
Electrical properties
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Electrical properties of
engineering materials
normally refer to the
ability of a material to
conduct an electric
current
Electrical Properties
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Good conductors
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Poor conductors
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All metals and carbon
Stone, wood and cotton,
air, glass
Very bad
conductors(insulators)
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Air, glass, silk pure rubber,
oils, paper, most plastics and
most ceramics
Chemical properties
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The chemical
property of a
material that is a
real concern to an
engineer is the
materials ability to
resist corrosion or
rust.
Optical properties

Sandalwood brings sweet
smell of success
From 1990 to 2002, the sale price of
sandalwood sold in India increased from
US$4 per kg to US$32 per kg. In addition
there has been a steep rise in sale price
from the year 2002 to 2006 to over
US$100 per kg.
may or may not be of
importance, although
such properties as
colour and luster often
assist in the
identification of a
material.