Material Science - eircom.net

concretecakeUrban and Civil

Nov 29, 2013 (3 years and 7 months ago)

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Materials Science


Introduction to Materials


Properties of Materials


Metals


Plastics


Woods


Composites


Heat Treatment

Introduction to Materials


Materials are used to make or build objects.


During the past 200 years there has been an
enormous increase in the range of materials
available to us. It is therefore important that the
correct materials be used for a particular use.


In Selecting the best material you need to look
at 4 things:
Physical properties,

Cost and Time,
Shaping and Forming

and Availability.


Selecting the best material


A checklist

2 WHAT COST?



The materials

The extras (fittings etc)

3 SHAPING & FORMING

Cutting out
Moulding
Casting
Joining

4 AVAILABILITY

Are they easy to obtain
including fittings.

1 PHYSICAL PROPERTIES

Hardness

Tensile Strength

Compressive Strength

Shear Strength

Stiffness

Toughness

Malleable

Corrosive

Appearance

Weight

Conductivity

S
E
L
E
C
T
I
O
N

Properties of Materials



Each material has many properties. It is
incorrect, for example to describe a material
as just ‘strong’ or ‘weak’ as for example
concrete is strong in compression but weak
in tension.

Hardness

Toughness


Strength

Brittleness

Malleability

Ductility

Elasticity

Plasticity

Conductivity

Density

Fatigue

Stiffness

Hardness


The ability of a material to resist wear
indentation and scratching.

An example of a
hardness test that
can be carried
out in the lab.

Different materials
are used and the
depth of indentation
measured

Toughness


The ability of a material to withstand
blows or sudden impact.

Different materials are
used, the hammer is
swung from the same
height each time about
a fixed fulcrum. The
distance travelled
after impact or
fracture is used to find
toughness

Strength


The ability of a material to withstand
forces of tension, compression and torsion

Tensile Strength



the ability to withstand
pulling forces or
Tension forces

Compressive Strength



the ability to withstand
‘squeezing’ forces or
Compression forces

Torsional Strength



the ability to withstand
‘twisting’ forces or
Torsion forces

Brittleness

The same as the
toughness test
however those
materials that
fracture easily
are said to be
brittle.


A material that is easily fractured by
impact is said to be brittle e.g. Glass

Malleability


A material that can be rolled or hammered
into shape without rupture.

As ring rises
the side of
Coke can is
thinned out

Ductility


A material that can be pulled or stretched
into a thin wire or thread.

Get picture of wire
drawing

Elasticity


The ability of a material to return to its
original shape after deformation.

Get picture of someone
stretching elastic band

Plasticity


The ability of a material to be permanently
deformed without fracture..

Conductivity


The ability of a material to allow Heat or
electricity to flow through it.

Ball Bearing
drops from
most

conductive 1
st
.

Density


Is the mass of 1 cubic centimetre (cm
3
) of a
substance. (Mass per unit Volume)

Q.
Which is heavier a tonne of feathers or
a tonne of lead?

Q. Which has the greatest density?

Density =

Mass

Volume

Fatigue


Occurs when materials have become
overworked and fracture or fail.

Find picture

Stiffness


The ability of a material to resist bending
deformation.

Metals



There are two types of metals



Ferrous



Non
-

Ferrous



Ferrous Metals

All the metals in this group contain
Iron
.
They include wrought iron, mild steel and
cast steel. Ferrous metals rust easily when
exposed to the atmosphere and are
magnetic.

Plain Carbon Steels

Alloy Steels

Plain Carbon Steels

These steels are a series of iron and
carbon alloys with carbon content
varying between 0.05% and 1.4%

Dead mild Steel


Low carbon content 0.05
-
0.15%.


Ductile and easily formed


Uses:

chains, rivets, nails, thin wire

Mild Steel


carbon content 0.15
-
0.30%.



Bright mild and Black mild, Bright mild
used in benchwork Black mild used for
forging


Ductile, easily cut, machined and welded,
cannot be hardened or tempered


Uses:

General engineering work, girders,
plates for ship building, gates.

Medium Carbon Steel


carbon content 0.30
-
0.60%.


Greater strength than mid steel but not as
ductile or malleable.


Uses:

Axles, rail tracks,spades wire ropes..

High Carbon Steel (Cast Steel)


carbon content 0.6
-
1.4%.


Hard and wear resistant can be hardened
and tempered.


Uses:

Cutting tools (chisels, saws, files)
dies punches springs hammers..

Silver Steel


carbon content @ 1.0%, contains chromium


Does not contain silver gets its name from
appearance


Uses:
Scribers and screwdriver heads.

Tool Steel



Used for making engineering tools.

Tinplate


Tinplate is produced by coating thin
sheets of steel containing 0.1% carbon
with Tin.


The process of coating the steel is called
Electro
-
plating.



Uses:

for food containers. It is also used
as containers for many other products such
as paint, lubricants etc.

Galvanised Iron



This is mild steel coated with Zinc.


The coating is usually achieved by
dipping the steel article in a bath of molten
zinc.


Uses:

for roof sheeting, gates, water
tanks, dust bins and other outdoor articles.


Alloy Steels

These steels are produced from adding
elements such as chromium, tungsten,
nickel and manganese to steel.