Assisting in Material Testing: Identifying Engineering Materials

ASSISTING IN MATERIAL TESTING
NOMINAL DURATION: 30Hrs
By:- Aragaw G/Medhin
January-2015

CONTENTS
 At the end of the module the trainee will be able to:
LO1. Identify engineering materials
LO2. Identify class of materials based on
properties
LO3. Identify and use sources of information on
engineering materials
 LO4. Prepare materials and equipment for testing
 LO5. Record and report results of material
By Aragaw G. 2

LO1: Identify common engineering
materials
1. Introduction
 Materials science is the scientific and
technological study of engineering materials.
 The materials sciences consist of six branches, five
of which are devoted to a particular class of
engineering materials.
By Aragaw G. 3

Introduction………..
 These five branches are
 Metallurgical engineering,
 Ceramic engineering,
 Polymer engineering,
 Composite engineering, and
 Surface engineering.
 Materials engineering is the final branch,
and it compares the properties of the
various classes of engineering materials.
By Aragaw G. 4

 Metallurgy is a branch of material science which
is defined as :- The science and technology of
extracting metals from their natural sources and
preparing them for practical use.
 It involves
 Mining.
 Concentrating ores.
 Reducing ores to obtain free metals.
 Purifying metals.
 Mixing metals to form alloys that have the
properties desired.
By Aragaw G. 5

Metallurgy
 In general Metallurgy can be classified as:
1. Extractive metallurgy
2. Mechanical metallurgy
3. Physical metallurgy
By Aragaw G. 6

Chapter 1 — Introduction to Metallurgy
1. Extractive metallurgy
 is the study of the extraction and
purification of metals from their ores.
 It is the practice of removing valuable
metals from an ore and refining the
extracted raw metals into a purer form
in order to convert a metal oxide or
sulfide to a purer metal, the ore must be
reduced physically, chemically, or
electrolytically.
Introduction….

2. Mechanical metallurgy is the study of
the techniques and mechanical forces that
shape finish forms of metals.
 Mechanical metallurgy studies the effects of
stress, time, temperature, etc. on metal.

3. Physical metallurgy
 Is the study of the effect of crystal structures
and microstructures on the properties of
metals.
 The two structures
studied in physical
metallurgy are the
crystal structure
and microstructure.

II. Classification of common engineering
Materials
 A large numbers of engineering materials exists
in the universe such as metals and non-metals.
 Engineering materials may also be categorized
into metals and alloys, ceramic materials,
organic polymers, composites and
semiconductors.
 The metal and alloys have tremendous
applications for manufacturing the products
required by the customers.
 Some commonly used engineering materials are
broadly classified as:- By Aragaw G. 11

General Classification of engineering
Materials
By Aragaw G. 12

Classification of common
engineering Materials
By Aragaw G. 13

1. Metals
 Is a solid material which is typically hard, shiny,
malleable, fusible, and ductile, with good electrical
and thermal conductivity,
e.g. iron, copper, and silver, gold and silver.
 Metallic materials are normally combinations of
metallic elements (Fe, Cu,Al, etc.).
 They have large numbers of non localized electrons.
 It can be categorized as
I. Ferrous Metals.
II. Non-Ferrous Metals.
By Aragaw G. 14

Metals
Non-ferrous
Ferrous
Metals
•aluminum
•brass
•bronze
•copper
•lead
•magnesium
•nickel
•tin
•titanium
•tungsten
•zinc
•cast iron
•carbon steel
•alloy steel
•stainless steel
Back***
By Aragaw G. 15

Several uses of steel and pressed
aluminum.
Metallic products
By Aragaw G. 16

2. Ceramics
 Is a material made of clay that is permanently
hardened by heat.
 Ceramics are compounds between metallic
and nonmetallic elements.
 Ceramics is inorganic compounds of one or
more metals with a nonmetallic element.
 They are most frequently oxides, nitrides, and
carbides (SiO2,Al2O3, Si3N4, BN, SiC,WC,
etc.).
By Aragaw G. 17

Structure:
(1) Amorphous or glass-short range order,
(2) crystalline (long range order) &
(3) crystalline material bonded by glassy matrix.
Classification:
 White wares, Glass, Refractory, Structural clay
products & Enamels.
Characteristics:
 Hard & brittleness,
 low mechanical & thermal shock
 High melting points
 Thermal conductivities between metal &
polymer
Ceramics
By Aragaw G. 18

Ceramics
Ceramics
•alumina
•beryllia
•diamond
•magnesia
•silicon carbide
•silicon nitride
•zirconia
By Aragaw G. 19

Examples of ceramic materials ranging from household to high
performance combustion engines which utilize both metals and
ceramics.
Ceramics
By Aragaw G. 20

 Polymers are Organic compounds that are
chemically based on carbon, hydrogen, and other
nonmetallic elements and they have very large
molecular structure consisting of many mers.
 Plastics are commonly known as synthetic resins
or polymers.
 In Greek terminology, the term polymer
comprises ‘poly’ means ‘many’ and ‘mers’
means ‘parts’.
Thus, the term, polymer represents a substance
built up of several repeating units (many identical
small molecules), each unit being known as a
monomer.
3. Polymers/Plastics
By Aragaw G. 21

 Thousands of such units or monomers join together
in a polymerization reaction to form a ‘polymer’.
 Some natural polymers like starch, resins, shellac,
cellulose, proteins, etc are vary common in today’s
use.
 Synthetic polymers possess a number of large
applications in engineering work.Therefore plastic
materials are fairly hard and rigid and can be readily
molded into different shapes by heating or pressure
or both.
 Plastics are broadly classified into thermo plastics
and thermo-setting plastics.
Polymers/Plastics
By Aragaw G. 22

Elastomers
Thermosets
Thermoplastics
Polymers
butyl
fluorocarbon
neoprene
nitrile
polysulfide
rubber
silicone
alkyd
epoxy
melamine
phenolic
polyester
urethane
ABS
acetal
acrylic
nylon
polycarbonate
polyethylene
polypropylene
polystyrene
vinyl
Natural and
synthetic rubbers
Polymers/plastics
By Aragaw G. 23

Polymers
include
“Plastics”
and
rubber
materials
Polymers
By Aragaw G. 24

4. COMPOSITES
 A composite material can be broadly defined
as an assembly two or more chemically
distinct material, having distinct interface
between them and acting to produce desired
set of properties
 Composites are mixture of materials such as
metal and alloys and ceramics, metals and
organic polymers, ceramics and organic
polymers.
 Examples:Vinyl coated steels, steel reinforced
concrete, fiber reinforced plastics, carbon
reinforced rubber etc. By Aragaw G. 25

Composite materials
 Polymer-matrix composites
 Cement-matrix composites
 Metal-matrix composites
 Carbon-matrix composites
 Ceramic-matrix composites
By Aragaw G. 26

 Composites are Mostly developed to improve
mechanical properties i.e strength, stiffness, creep
resistance & toughness.
 Three type of composite
(1) Dispersion-strengthened,
(2) Reinforcement – continuous & discontinuous
(3) Laminated (consist more than 2 layers bonded
together).
Applications
 These materials are used for making sports
items, structures, and electrical devices.
Composite…
By Aragaw G. 27

Composites
carbon fiber
ceramic matrix
glass fiber
Kevlar
metal matrix
Composites
By Aragaw G. 29

Composites
Carbon fiber Style 282 bidirectional.
Araldite epoxy resin with HY956
additive.
Manufacturing process
By Aragaw G. 30

Composites
Ossur Flexwalk
College Park Foot
Otto Bock Advantage
Pie protésico dinámico
2004
Pie protésico dinámico
2005
By Aragaw G. 31

Composites
Marlon
Shirley
Ossur
Cheeta
Flex-Foot
Cameron
Clapp
Otto Bock
C-Leg
Date of birth:April 21, 1978
Hometown:Thatcher, Utah
Current Home:San Diego, CA
Date of birth: Sep 15, 1986
By Aragaw G. 32

Material
s Class
Definition Examples Properties Applications
Metals Metals are combinations of
one or more "metallic
elements," such as iron,
gold, or lead. Alloys are
metals like steel or bronze
that combine more than one
element, and may include
non-metallic elements e.g.
carbon.
Steel, aluminium,
titanium iron, gold,
lead, copper,
platinum, brass,
bronze, pewter,
solder
Strong, dense, ductile,
electrical and heat
conductors, opaque
Electrical wiring,
structures (buildings,
bridges), automobiles
(body, springs),
airplanes, trains (rails,
engine components,
body, wheels), shape
memory materials,
magnets
Ceramics Ceramic materials are
inorganic materials with non-
metallic properties usually
processed at high
temperature at some time
during their manufacture
Structural ceramics,
refractories,
porcelain, glass
Lower density than metals,
strong, low ductility (brittle),
low thermal conductivity,
corrosion resistant
Dinnerware, figurines,
vases, art, bathtubs,
sinks, electrical and
thermal insulation,
sewage pipes, floor and
wall tile, dental fillings,
abrasives, glass
windows
Polymers A polymer contains many
chemically bonded parts or
units that are bonded
together to form a solid.
Plastics (synthetic,
nylon, liquid crystals,
adhesives,
elastomers (rubber)
Low density, poor conductors
of electricity and heat,
different optical properties
Fabrics, car parts,
packaging materials,
bags, packing materials
(Styrofoam*), fasteners
(Velcro*), glue,
containers, telephone
headsets, rubber bands
Composites Composites are two or more
distinct substances that are
combined to produce a new
material with properties not
present in either individual
material.
Fibreglass (glass
and a polymer),
plywood (layers of
wood and glue),
concrete (cement
and pebbles)
Properties depend on
amount and distribution of
each type of material.
Collective set of properties
are more desirable and
possible than with any
individual material.
Golf clubs, tennis
rackets, bicycle frames,
tires, cars, aerospace
materials, paint
By Aragaw G. 33

 Basic Part of the metalworker’s skill lies is the ability
to identify various metal products brought to the
shop.
 The metalworker must be able to identify the metal
so the proper work methods can be applied.
 For Army equipment, drawings should be available.
They must be examined in order to determine the
metal to be used and its heat treatment (if required).
 If no drawing is available, knowledge of what the
parts are going to do will serve as a guide to the
type of metal to use
III. Metal identification methods
By Aragaw G. 34

Metal identification methods……
 What characteristics are used to identify metals?
 The ability to judge metals can be developed only
through personal experience, practice these tests
with known metals until familiar with the reactions
of each metal to each type of test.
 Physical and chemical tests are used to determine
the type of metal.
1. The Appearance Test
2. The Magnetic Test
3. The ChiselTest
4. The Fracture Test
5. The FlameTest
6. The SparkTest
7. Manufacturers stamp
By Aragaw G. 35

1.The Appearance Test
 Involves identification of a metal by its appearance
and use.
 Color and appearance make certain metals such as
copper, brass, and bronze easy to identify.
By Aragaw G. 36

2.The Magnetic Test
 Involves identification of metal by the use
of a magnet.
By Aragaw G. 37

3.The Chisel Test
 involves identification of metal by the use
of a hammer and cold chisel.
By Aragaw G. 38

4.The Fracture Test
 Involves identification of metal by
fracturing the metal and observing the
grain.
 Some metals can be quickly identified by
looking at the surface of the broken part
or by studying the chips produced with a
hammer and chisel.
By Aragaw G. 39

5.The Flame Test
 Involves identification of metals by
applying a flame to them and watching
what occurs.
By Aragaw G. 40

6.The Spark Test
 This is a simple identification test used to
observe the color, spacing, and quantity of
sparks produced by grinding.
 It is a fast and convenient method of sorting
mixed steels with known spark
characteristics.
 This test is best conducted by holding the
steel stationary and touching a high-speed
portable grinder to the steel with sufficient
pressure to throw a spark stream about 12
inches long. By Aragaw G. 41

 The color, shape, average length, and activity of
the sparks are characteristics of the material
being tested.
 These spark patterns provide general
information about the type of steel, cast iron,
or alloy steel.
 In all cases, it is best to use standard samples of
metal when comparing their sparks with that
of the test sample.
 The characteristics of sparks generated by a
spark grinding test are shown in Figure –below.
The Spark Test……..
By Aragaw G. 42

 Perhaps the best known numerical code is the Society of
Automotive Engineers (SAE) code.
 For the metals industry, this organization pioneered in
developing a uniform code based on chemical analysis.
 The SAE system is based on the use of four-or five digit
umbers.
The first number indicates the type of alloy used; for
example, 1- indicates a carbon steel.
2- indicates nickel steel.
The second, and sometimes the third, number gives the
amount of the main alloy in whole percentage numbers.
The last two, and sometimes three, numbers give the
carbon content in hundredths of 1 percent (0.01
percent).
7. The Manufacturers stamp
By Aragaw G. 44

The Manufacturers stamp……..
SAE 1045
1- Type of steel (carbon).
0- Percent of alloy (none).
45- Carbon content (0.45-percent carbon).
SAE 2330
2- Type of steel (nickel).
3- Percent of alloy (3-percent nickel).
30- Carbon content (0.30-percent carbon).
SAE 71650
7- Type of steel (tungsten).
16- Percent of alloy (16-percent tungsten).
50- Carbon content (0,50-percent carbon).
SAE 50100
5- Type of steel (chromium).
0- Percent of alloy (less than l-percent
chromium)
100- Carbon content (1-percent carbon).
By Aragaw G. 45

Student Activity-1 15% marks
Select at least three materials available in your
shop, Identify the various types of metals
using the above methods and write your
observation in detail:
By Aragaw G. 47

 Materials are used to make or build objects.
 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:
1. Material properties,
2. Cost and Time,
3. Shaping and Forming and
4. Availability.
IV. Selection of engineering materials
By Aragaw G. 49

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 MATERIAL PROPERTIES
Conductivity
Appearance
Weight
Corrosive
Hardness
Tensile Strength
Compressive Strength
Shear Strength
Stiffness
Toughness
Malleable
S
E
L
E
C
T
I
O
N
By Aragaw G. 50

Selection of engineering materials
 In general; Selection of Materials basically
depends on the following characteristics:-
1. Product function interdependence
2. Material property (Mechanical properties
Physical properties)
3. Families of materials
4. Materials first screening
By Aragaw G. 51

1. Product function is interdependent
Material
Properties
Manufacturing
Processes
Product
Geometry
Product
Function
By Aragaw G. 52

2. Material properties
 Mechanical properties
 Quantities that characterize the behavior of a
material in response to external, or applied forces.
 Quantities that characterize the behavior of a material
in response to physical phenomena other than
mechanical forces …(e.g. such as heat, electricity,
radiation)
 Physical properties
By Aragaw G. 53

Characteristics Metals Ceramics Polymers
strength strong
strong –C
weak –T
weak
elastic strength very some some
stiffness very very flexible
ductility ductile brittle ---
hardness medium hard soft
corrosion resistance poor good excellent
fatigue resistance good --- ---
conductivity (heat/electric) conductor insulator insulator
creep resistance good --- poor
impact resistance good poor good
density heavy medium light
temperature tolerance good super poor
3. Property profiles by family
By Aragaw G. 54

4. Materials selection/Screening
prospective
materials and processes
screening
rating
Rejected materials
and processes
best
material(s) and processes
functional?
manufacturable?
relative
performance?
Feasible materials and
processes
By Aragaw G. 55

Using Material Selection Charts
By Aragaw G. 56

Selection of engineering materials….
 The reasons for selecting the materials can be
summarized as :
1. Commercial factors such as:
 Cost, availability, ease of manufacture.
2. Engineering properties of materials such as:
Electrical conductivity,
strength, toughness,
ease of forming by extrusion,
forging and casting,
machinability and corrosion resistance.
By Aragaw G. 57

LO2. Identify class of materials
based on properties
By Aragaw G. 58

2.1. classification of metals
depend on d/t parameters
 All metals may be classified as Ferrous or Non-
Ferrous. ***
 A Ferrous metal has iron as its main element.
 A metal is still considered ferrous even if it contains
less than 50 percent iron, as long as it contains
more iron than any other one metal.
◦ Ferrous metals include cast iron, steel, and the
various steel alloys
◦ The only difference between iron and steel is the
carbon content.
 Cast iron contains more than 2-percent carbon,
while steel contains less than 2 percent.
By Aragaw G. 59

Ferrous metals
 They are the strongest materials available and are
used for applications where high strength is
required at relatively low cost and where weight is
not of primary importance.
 As an example of ferrous metals such as : bridge
building, the structure of large buildings, railway
lines, locomotives and rolling stock and the
bodies and highly stressed engine parts of road
vehicles.
 The ferrous metals themselves can also be
classified as Steel, Cast iron and Wrought iron, as
shown in figure 4.
By Aragaw G. 60

Non – ferrous metals
 A metal is nonferrous if it contains less
iron than any other metal.
◦ Nonferrous metals include a great many
metals that are used mainly for metal plating
or as alloying elements, such as tin, zinc, silver,
and gold.
 These materials refer to the remaining metals
known to mankind.
 The pure metals are rarely used as structural
materials as they lack mechanical strength.
By Aragaw G. 62

Non – ferrous metals
 They are used where their special properties such
as corrosion resistance, electrical conductivity and
thermal conductivity are required.
 Copper and aluminum are used as electrical
conductors and, together with sheet zinc and
sheet lead, are use as roofing materials.
 They are mainly used with other metals to
improve their strength.
 The non-ferrous metals themselves can also be
classified as shown in figure 5.
By Aragaw G. 63

2.2. properties of engineering
materials
General Properties of Engineering Materials
 The principle properties of materials which are of
importance to the engineer in selecting materials.
These can be broadly divided into:
1. physical properties
2. Mechanical properties
3. Chemical properties
4. Thermal properties
5. electrical properties
6. magnetic properties etc. *******
By Aragaw G. 65

1. Physical properties of materials
 Physical properties is defined as quantities that
characterize the behavior of a material in response
to physical phenomena other than mechanical
forces …(e.g. such as heat, electricity, radiation)
 These properties concerned with such properties
as:
Melting,
Temperature,
Electrical conductivity,
Thermal conductivity,
Density,
Corrosion resistance,
Magnetic properties, etc.
By Aragaw G. 66

2. Mechanical properties
 Mechanical properties is defined as:
quantities that characterize the behavior of
a material in response to external, or
applied forces
 Mechanical properties are useful to
estimate how parts will behave when they
are subjected to mechanical loads (stresses)
 Some of the Mechanical properties are, Strength,
Hardness, Ductility,Toughness, Fatigue resistance,
Creep, etc.
By Aragaw G. 67

Important engineering characteristics
of materials
 Chemical properties
 Oxide or Compound
Composition
 Acidity or Alkalinity
 Resistance to Corrosion or
Weathering
 Reactivity
 Combustibility
 Thermal properties
Thermal conductivity
Coefficient of expansion
Melting point
Specific Heat
Expansion
 Electrical and
magnetic properties
◦ Conductivity
◦ Magnetic permeability
◦ Galvanic action
 Optical properties
◦ Colour
◦ Transmissivity
 Light transmission
 Light reflection
By Aragaw G. 68

Student Activity-2 15% marks
Write a detail explanation about the following
material properties:
 HardnessVs Toughness
 StrengthVs Brittleness
 MalleabilityVs Ductility
 ElasticityVs Plasticity
 ConductivityVs Density
 FatigueVs Stiffness By Aragaw G. 69

By Aragaw G.
2.3. Applications of engineering
materials
I. Structural applications
II. Electronic applications
III. Thermal applications
IV. Electrochemical applications
V. Environmental applications
VI. Biomedical applications
70

I. Structural applications
 Buildings, bridges, piers,
highways, landfill cover
 Aircraft, satellites, missiles
 Automobiles (body,
bumper, shaft, window,
engine components, brake,
etc.)
 Bicycles, wheelchairs
 Ships, submarines
 Machinery
 Tennis rackets, fishing rods,
skis
 Pressure vessels, cargo
containers
 Furniture
 Pipelines, utility poles
 Armor, helmets
 Utensils
 Fasteners
 Repair materials
By Aragaw G. 71

II. Electronic applications
 Electrical circuitry (resistors, capacitors, inductors)
 Electronic devices (diodes, transistors)
 Optoelectronic devices (solar cells, light sensors, light-
emitting diodes)
 Cables, Connectors, Power supplies
 Motors
 Electrical contacts, brushes (sliding contacts)
 Optical fibers (materials of low optical absorptivity for
communication and sensing)
 Absorbers, reflectors and transmittors of electromagnetic
radiation
 Photography
 Photocopying
By Aragaw G. 72

III. Thermal applications
 Heating and cooling of buildings
 Industrial heating (casting, annealing,
deicing, etc.)
 Refrigeration
 Microelectronic cooling
 Heat removal (brakes, cutting, welding,
chemical reactions, etc.)
By Aragaw G. 73

IV. Electrochemical applications
 Batteries
 Fuel cells (galvanic cells in which the
reactants are continuously supplied, e.g.,
the hydrogen-oxygen fuel cell)
V. Environmental protection
 Pollutant removal (e.g., filtration, absorption by
activated carbon)
 Reduction in the amount of pollutant generated
(e.g., use of biodegradable polymers)
 Recycling
 Electronic pollution control By Aragaw G. 74

VI. Biomedical applications
 Diagnosis
 Treatment
 Biomedical materials and devices
• Implants
• Bone replacement materials
• Bone growth support
• Surgical and diagnostic devices
• Wheelchairs
• Devices for helping the disabled
• Exercise equipment
• Pharmaceutical packaging
• Instrumentation hip replacements
By Aragaw G. 75

3.1. Extraction of metals
LO3: Identification and use sources
of information on engineering
materials

By Aragaw G.
Introduction
Most metals are found naturally in rocks
called ores.They are in compounds,
chemically bonded to other elements
iron ore
77

By Aragaw G.
Native
Some unreactive metals can be found as
elements.They are called native metals.
Au(gold) Ag(silver) copper
78

Principles of Metal extraction
 Most elements do not occur as separate
substances but exist naturally as
compounds.
 Metals tend to exist as metal oxides as
part of ores which are excavated from
the earth.
 To recover the metal from it’s oxide the
metal ion is split from the oxygen ion.
 Metals high up on the activity series have
more stable oxides than those lower
down and due to this are more difficult to
split up than those lower down.
By Aragaw G. 79

 The method used to extract a metal from its ore is guided
by the position of the element on the Reactivity Series.
 Metals high up on the series are strongly bonded in their
compounds. Electrolysis is the only method strong
enough to extract these.
Example:
Na(sodium), Mg(magnesium) and Al(aluminium)
 Metals in the middle of the series are less strongly
bonded in their compounds.
 Their oxides can be reduced by carbon to give the metal.
Example:
Zn(zinc) and Fe(iron)
2 ZnO(s) + C(s) 2 Zn(s) + CO2(g)
zinc oxide+carbon zinc+carbon dioxide
Methods of metal extraction:
By Aragaw G.
80

 Metals at the bottom of the series can
be found uncombined in nature.
They simply need to be purified of
unwanted materials.
When they do occur in ores, example
copper sulphide, heating is strong enough
to displace the metal from the ore.
Example:
Cu(copper),Ag(silver) and Au(gold)
Methods (CONT…)
By Aragaw G. 81

1.What is electrolysis?
 Electrolysis is a process that uses electricity to
separate the elements in a compound.The word
electrolysis means ‘splitting with electricity’.
 Aluminium is a reactive metal that is
found in the ore bauxite. It is combined
with oxygen as aluminium oxide.
 Electrolysis is used to remove the
oxygen and extract aluminium, which
means that reduction takes place.
What is the word equation for the extraction of aluminium?
aluminium oxide aluminium oxygen
= +
 Electrolysis is expensive and so it is only used
to extract reactive metals that cannot be
extracted in other ways.
By Aragaw G. 82

Metals are often found combined with oxygen as oxides.To
obtain the metal, the oxygen must be removed.
In this reaction, the carbon removes oxygen from lead oxide.
This occurs because carbon is more reactive than lead.
II.What is reduction?
The removal of oxygen from a substance is called reduction.
Carbon can be used to extract metals by reduction.
lead oxide + carbon lead
carbon
monoxide
= +
PbO C Pb CO
+ +
=
metal oxide (in ore) metal
reduction
The addition of oxygen to a substance is called oxidation.
By Aragaw G. 83

Which metals does carbon reduce?
A metal can be reduced by carbon if it is
less reactive than carbon and so appears
below carbon in the reactivity series.
If a metal is more reactive than carbon,
other chemical reactions and processes
must be used in its extraction.
Certain metals, such as iron, can be only
be reduced using carbon if they are
heated to very high temperatures.
potassium
sodium
calcium
magnesium
aluminium
zinc
iron
copper
gold
lead
silver
(carbon)
(hydrogen)
platinum
By Aragaw G. 84

III. Heating of the ore
 Metals at the bottom of the series can be found
uncombined in nature.
 They simply need to be purified of unwanted
materials.
 When they do occur in ores, example copper
sulphide, heating is strong enough to displace the
metal from the ore.
Example: Cu(copper),Ag(silver) and Au(gold)
silver oxide sliver + oxygen
By Aragaw G. 85
HEAT

1.Electrolyis:
 Most powerful means of extraction.
 most expensive.
 Can only be used where electricity is abundant.
II. Reduction with carbon(carbon monoxide)
 Cheaper to operate than electrolysis.
 Labour intensive .
 Expensive to start-up as large industrial equipment is
used.
III. Heating of the ore.
 Cheap
 Can only be used on the most unreactive of metals
(Mercury, gold, silver, etc.) By Aragaw G. 86
Methods Summary

Extraction of ferrous metal
(Iron)
The extraction of Iron is a reductive process
whereby oxygen is removed from the iron oxide
by carbon monoxide.
The process occurs within a Steel blast furnace
lined with refractive(fire) bricks at temperatures
from 8000C up to 19000C.
The Chamber is kept hot by jets of hot air at over
8000C, giving it the name “Blast” furnace.
By Aragaw G. 87

 Start materials:
1. Iron Ore or Hematite
2. Lime or Calcium carbonate CaCO3
3. Coke a carbonaceous ashy substance
Iron Ore
Lime
Coke
By Aragaw G. 88

Extraction of Iron: Step1 Burning of Lime
 Iron ore, limestone(CaCO3)
and coke are delivered to the
top of the blast furnace, where
the temperature is around
8000C.
 The lime stone burns at 8000C
yielding calcium oxide(CaO)
and Carbon Dioxide(CO2).
• CaCO3 -> CaO + CO2
 The Calcium oxide causes
impurities which are present
with the ore to fall as a
precipitate near to the bottom
producing a layer of “slag”.
By Aragaw G. 89

Step 2 Production of Carbon Monoxide
 The carbon Dioxide yielded
from the Burning of Lime
passes over the coke.
 Coke is a coal like substance
produced from the heating of
Tar and Petrochemicals
without heat and contains a
high percentage of carbon.
 The Carbon atoms of coke
remove a single oxygen from
each molecule of CO2
producing carbon monoxide
 CO2 + C 2 CO
Coke
By Aragaw G. 90

Step 3 Reduction of Iron
 The Carbon monoxide yielded
from the reaction of Carbon
dioxide and lime removes the
oxygen from Iron oxide.
 Each Carbon monoxide
molecule is capable of binding a
single oxygen so 3 are used to
completely remove all oxygen
from the iron oxide.
Fe2O3 + 3 CO -> 2Fe(s) + 3 CO2
 The molten iron sinks to the
bottom lowest level of the
furnace, where it can be tapped off.
 The iron produced by this
process is called pig iron and is
95% pure.
By Aragaw G. 91

Extraction of Iron: summery
 Production of iron from it’s
ore uses Carbon monoxide
to reduce Iron oxide to iron
atoms.
1.Lime burns
• CaCO3 = CaO + CO2
2. CO2 reduced by coke to CO
• CO2 + C = 2 CO
3. Iron oxide reduced by CO
• Fe2O3 + 3CO = 2Fe + 3CO2
Removes impuritiies
: slag production
By Aragaw G. 92

The Extraction Of non ferrous Metals
(Aluminium)
 Aluminium is very abundant in the earth’s crust, but
is never found in its free state.
 Aluminium is found mainly in the form of
aluminosilicates, of which bauxite (Al2O3) is the
chief source.
 The crude/mined bauxite is either: heated to
3000oC to produce calcined bauxite Converted to
pure alumina (Al2O3)
 The process for extracting aluminium from aluminia
is electrolysis.
By Aragaw G. 93

 Electrolysis is the process by which the passage
of an electric current through a substance causes
it to decompose.
 In the current process of extracting aluminium
from bauxite, an electrolytic cell made of steel
using graphite electrodes is used.
 The current used is 100,000A and the
temperature is 1,223K.
 Pure aluminia (aluminium oxide) which melts at
2050oC is dissolved in molten cryolite (sodium
aluminium fluoride), Na2AlF6.
 The addition of the cryolite lowers the
temperature to 950oC, because the presence of an
impurity lowers the melting point of a substance.
By Aragaw G. 94

 The presence of the cryolite also gives the
melt better conducting properties and, in
addition, it does not mix with the aluminium
metal formed in the electrolysis.
 Aluminium is discharged at the graphite
cathode, which lines the chamber.
 The product is 99% pure, the chief impurities
being silicon and iron.
Liquid aluminium is tapped off at the end of the cell.
Al3+
(l) + 3e- Al(l)
Oxygen is the other product that is produced at the
anode.
2O2-
(l) - 4e- O2(g)
By Aragaw G. 95

Electrolysis of Aluminium.
By Aragaw G. 96

Uses of Aluminum
Uses Properties
Overhead
electric cables
Low density, light
Resistant to corrosion
(protected by aluminium oxide)
Good electrical conductivity
Food containers Non-toxic
Good conductor of heat
Aircraft body Low density, light
High tensile strength
By Aragaw G. 97

3.2.Testing of materials
 Testing processes will be divided into the
following two major groups:
1. Destructive testing:- a process that
causes an alteration(changing) of the
surface or of the microstructure of the
materials.
2. Nondestructive testing:- a test that can
be conducted without altering (changing)
the usefulness of the material
By Aragaw G. 98

Destructive testing vs Non-destructive
testing
 Destructive testing
 is carried out until the specimen’s failure.
These tests are generally much easier to carry
out, yield more information and are easier to
interpret than non-destructive testing
 Non-destructive testing
is the type of testing that does not destroy the
test object.
It is vital when the material in question is still in
service.
By Aragaw G. 99

I. Destructive testing
 Destructive testing are:-
1. Hardness tester – Rockwell and brinell
2. Spark testing – grinder ( portable, bench)
3. Tensile tester
4. Impact testing equipment ( charpy test)
5. Compression testing
6. Bend testing
7. Chemical analysis
8. Hydrostatic testing to destruction
9. Peel testing etc
NB:- Some ofThe above type of tests can be discussed in
LO-4 ***** By Aragaw G. 100

Definition of NDT:
 The use of noninvasive
techniques to determine the
integrity of a material,
component or structure
or
 Quantitatively measure some
characteristic of an object. i.e.
Inspect or measure without
doing harm.
By Aragaw G. 101
II. Nondestructive testing(NDT)

Methods of NDT
Visual
By Aragaw G. 102

What are Some Uses of NDT
Methods?
 Flaw(error) Detection and Evaluation
 Leak Detection
 Location Determination
 Dimensional Measurements
 Structure and Microstructure Characterization
 Estimation of Mechanical and Physical Properties
 Stress (Strain) and Dynamic Response
Measurements
 Material Sorting and Chemical Composition
Determination
By Aragaw G. 103

When are NDT Methods Used?
 To assist in product development
 To screen or sort incoming materials
 To monitor, improve or control manufacturing
processes
 To verify proper processing such as heat
treating
 To verify proper assembly
 To inspect for in-service damage
By Aragaw G.
There are NDT application at almost stage in the
production or life cycle of a component
104

Six Most Common NDT Methods
1. Visual
2. Liquid Penetrant
3. Magnetic
4. Ultrasonic
5. Eddy Current
6. X-ray
By Aragaw G. 105

 Most basic and common
inspection method.
 Tools include
fiberscope, borescope,
magnifying glasses and
mirrors.
Robotic crawlers permit observation
in hazardous or tight areas, such as air
ducts, reactors, pipelines.
 Portable video inspection
unit with zoom allows
inspection of large tanks
and vessels, railroad tank
cars, sewer lines.
1.Visual Inspection
By Aragaw G. 106

 A liquid with high surface wetting
characteristics is applied to the surface of
the part and allowed time to seep into
surface breaking defects.
 The excess liquid is removed from the
surface of the part.
 A developer (powder) is applied to pull the
trapped penetrant out the defect and spread
it on the surface where it can be seen.
 Visual inspection is the final step in the
process. The penetrant used is often loaded
with a fluorescent dye and the inspection is
done under UV light to increase test
sensitivity.
2. Liquid Penetrant Inspection
By Aragaw G. 107

3. Magnetic Particle Inspection
 The part is magnetized. Finely(lightly) milled iron particles
coated with a dye pigment are then applied to the specimen.
 These particles are attracted to magnetic flux leakage fields
and will cluster to form an indication directly over the
discontinuity.
 This indication can be visually detected under proper
lighting conditions.
By Aragaw G. 108

Magnetic Particle Crack Indications

4. Radiography
 The radiation used in radiography testing
is a higher energy (shorter wavelength)
version of the electromagnetic waves
that we see as visible light.
 The radiation can come from an X-ray
generator or a radioactive source.
High Electrical Potential
Electrons
-
+
X-ray Generator
or Radioactive
Source Creates
Radiation
Exposure Recording Device
Radiation
Penetrate
the Sample
By Aragaw G. 110

Film Radiography
Top view of developed film
X-ray film
The part is placed between the radiation
source and a piece of film.
The part will stop some of the radiation.
Thicker and more dense area will stop
more of the radiation.
= more exposure
= less exposure
The film darkness (density)
will vary with the amount of
radiation reaching the film
through the test object.
By Aragaw G. 111

Radiographic Images
By Aragaw G. 112

Conductive
material
Coil
Coil's
magnetic field
Eddy
currents
Eddy current's
magnetic field
5. Eddy CurrentTesting
By Aragaw G. 113

Eddy CurrentTesting
Eddy current testing is particularly well suited for detecting
surface cracks but can also be used to make electrical
conductivity and coating thickness measurements.
 Here a small surface probe is scanned over the part surface
in an attempt to detect a crack.
By Aragaw G. 114

 High frequency sound waves are introduced into a material
and they are reflected back from surfaces or flaws.
 Reflected sound energy is displayed versus time, and inspector
can visualize a cross section of the specimen showing the
depth of features that reflect sound.
f
plate
crack
0 2 4 6 8 10
initial
pulse
crack
echo
back surface
echo
Oscilloscope, or flaw detector
screen
6. Ultrasonic Inspection (Pulse-Echo)
By Aragaw G. 115

Ultrasonic Imaging
Gray scale image produced using
the sound reflected from the front
surface of the coin
Gray scale image produced using the
sound reflected from the back surface
of the coin (inspected from “heads”
High resolution images can be produced by plotting signal
strength or time-of-flight using a computer-controlled
scanning system.
By Aragaw G. 116

Common Application of NDT
 Inspection of Raw Products
 Inspection Following Secondary
Processing
 In-Services Damage Inspection
By Aragaw G. 117

Inspection of Raw Products
 Forgings,
 Castings,
 Extrusions,
 etc.

 Machining
 Welding
 Grinding
 Heat treating
 Plating
 etc.
Inspection Following Secondary Processing

 Cracking
 Corrosion
 Erosion/Wear
 Heat Damage
 etc.
Inspection For In-Service Damage

Power Plant Inspection
Prob
e
Signals produced
by various
amounts of
corrosion thinning.
Periodically, power plants are
shutdown for inspection.
Inspectors feed eddy current
probes into heat exchanger tubes
to check for corrosion damage.
Pipe with damage
By Aragaw G. 121

Wire Rope Inspection
 Electromagnetic devices and
visual inspections are used to
find broken wires and other
damage to the wire rope that is
used in chairlifts, cranes and
other lifting devices.

Storage Tank Inspection
 Robotic crawlers use
ultrasound to inspect
the walls of large
above ground tanks
for signs of thinning
due to corrosion.
Cameras on long
articulating arms
are used to inspect
underground
storage tanks for
damage.
By Aragaw G. 123

Aircraft Inspection
Nondestructive testing is used
extensively during the
manufacturing of aircraft.
NDT is also used to find cracks
and corrosion damage during
operation of the aircraft.
A fatigue crack that started at
the site of a lightning strike is
shown below.

Jet Engine Inspection
Aircraft engines are overhauled
after being in service for a period
of time.
They are completely disassembled,
cleaned, inspected and then
reassembled.
Fluorescent penetrant inspection is
used to check many of the parts for
cracking.
By Aragaw G. 125

PressureVessel Inspection
 The failure of a pressure vessel
can result in the rapid release
of a large amount of energy.
 To protect against this
dangerous event, the tanks are
inspected using radiography
and ultrasonic testing.
By Aragaw G. 126

Rail Inspection
 Special cars are used to
inspect thousands of miles
of rail to find cracks that
could lead to a derailment.
By Aragaw G. 127

Bridge Inspection
The US has 578,000
highway bridges.
Corrosion, cracking and
other damage can all affect
a bridge’s performance.
The collapse of the Silver
Bridge in 1967 resulted in
loss of 47 lives.
Bridges get a visual
inspection about every 2
years.
Some bridges are fitted
with acoustic emission
sensors that “listen” for
sounds of cracks growing.
By Aragaw G. 128

 NDT is used to inspect pipelines
to prevent leaks that could
damage the environment.
 Visual inspection, radiography and
electromagnetic testing are some
of the NDT methods used.
Remote visual inspection using a
robotic crawler.
Radiography of weld joints.
Magnetic flux leakage inspection. This
device, known as a pig, is placed in the
pipeline and collects data on the
condition of the pipe as it is pushed
along by whatever is being
transported.
Pipeline Inspection
By Aragaw G. 129

Special Measurements
 Boeing employees in Philadelphia were given the privilege of
evaluating the Liberty Bell for damage using NDT
techniques.
 Eddy current methods were used to measure the electrical
conductivity of the Bell's bronze casing at various points to
evaluate its uniformity.
By Aragaw G. 130

INTRODUCTION
Significance of testing materials
 The testing of materials may be performed with one
of the three points below:
1. To supply routine information on the quality of a
product- commercial or control testing,
2. To develop new or better information on known
materials or to develop new materials- materials
research,
3. To obtain accurate measures of fundamental
properties of materials- scientific measurement.
LO4:- Prepare materials and
equipment for testing
By Aragaw G. 131

Why metals are tested ?
 Ensure quality
 Test properties
 Prevent failure in use
 Make informed choices in using materials
By Aragaw G. 132

What is the difference between experiments
and tests?
 Experimentation means that the outcome is
uncertain, that new insights are to be gained.
 Testing is a more defined procedure, with the
limits and results are clear. It concerned on the
functionality of an object/equipments.
By Aragaw G. 133
Materials testing may be carried out on:-
1. Full size structures, members, or parts,
2. Models of structures, members, or parts,
3. Specimens cut from finished parts,
4. Specimens of raw or processed materials,

Precision & Accuracy
 Precision: repeatability of a measurement
 Accuracy: its closeness to the true value
If an instrument consistently gives nearly
identical but wrong readings- precise but not
accurate
If readings vary considerably but do center
about the true value- accurate but not
precise
N.B.:- Test results should be both precise and
accurate!
By Aragaw G.

TENSILETESTING
MACHINE
By Aragaw G.
4. Common tools and Equipments use for
testing.
4.1.Testing equipments
METAL MICROSCOPE
MACHINE
IMPACTTESTING
MACHINE
135

4.1.1. Hardness testing
Fundamentals of Hardness
 Hardness is defined as the resistance to
penetration by an object or the solidity or firmness
of an object. It can be:
Resistance to permanent indentation under
static or dynamic loads
Energy absorption under impact loads (rebound
hardness)
Resistance to scratching (scratch hardness)
Resistance to abrasion (abrasion hardness)
Resistance to cutting or drilling (machinability)
By Aragaw G. 136

By Aragaw G.
 Principles of hardness (resistance to indentation)
Indenter: ball or plain or truncated cone or
pyramid made of hard steel or diamond
Load measured that yields a given depth
Indentation measured that comes from a
specified load
Rebound height measured in rebound test after
a dynamic load is dropped onto a surface
 Three common hardness measuring tests are
I. Brinell hardness test
II. Vickers hardness test
III. Rockwell hardness test
4.1.1. Hardness testing
137

Overview – Testing Materials
Hardness Testing
Direct Reading Hardness Testing
Machine (Vickers or Brinell)
Measures the materials resistance to indentation or scratching
Indenter
Test Component
Placed on Table
Table Height
Adjustment
Activating lever
Hardness Value
Read Directly From
Dial
By Aragaw G. 138

I. Brinell Test Method
 One of the oldest tests Invented by J.A. Brinell 1900
 It involves pressing a steel or carbide ball of 10mm against a
surface with various loads.(500, 1500, or 3000 kg)
 Static test that involves pressing a hardened steel ball
(10mm diameter) into a test specimen while under a load of
3000 kg load for hard metals,
1500 kg load for intermediate hardness metals
 500 kg load for soft materials
 Measures diameter of indentation.
 Harder surfaces have small indentation while softer
surfaces have larger
indentation.
By Aragaw G. 139

Types of Brinell tester
 Various types of Brinell by:-
Method of load application : oil pressure, gear-
driven screw, or weights with a lever
Method of operation: hand or electric power
Method of measuring load: piston with weights,
bourdon gage, dynamometer, or weights with a
lever
Size of machine: stationary (large) or portable
(hand-held)
By Aragaw G. 140

Brinell Test Method (cont…)
 Method
Specimen is placed on the anvil and raised to contact the
ball
Load is applied by forcing the main piston down and
presses the ball into the specimen
A Bourbon gage is used to indicate the applied load
When the desired load is applied, the balance weight on
top of the machine is lifted to prevent an overload on
the ball
The diameter of the ball indentation is measured with a
micrometer microscope, which has a transparent
engraved scale in the field of view
By Aragaw G. 141

 Units: pressure per unit area
 Brinell Hardness Number (BHN) = applied load divided by
area of the surface indenter
 
2
2
2
d
D
D
D
L
BHN




Where: BHN = Brinell Hardness Number
L = applied load (kg)
D = diameter of the ball (10 mm)
d = diameter of indentation (in mm)
• Example:What is the Brinell hardness for a specimen with an
indentation of 5 mm is produced with a 3000 kg applied load.
•Ans:
 
2
2
2
/
6
.
142
)
5
(
)
10
(
10
)
10
(
)
3000
(
2
mm
kg
mm
mm
mm
mm
kg
BHN 




By Aragaw G. 142

Typical HB values
Material Hardness
Soft wood (e.g., pine) 1.6 HBS 10/100
Hard wood 2.6–7.0 HBS 1.6 10/100
Aluminum 15 HB
Copper 35 HB
Mild steel 120 HB
18-8 (304) stainless steel annealed 200 HB
Glass 1550 HB
Hardened tool steel 1500–1900 HB
Rhenium diboride 4600 HB
By Aragaw G. 143

 Range of Brinell Numbers
 90 to 360 values with higher number indicating higher
hardness
 The deeper the penetration the higher the number
 Brinell numbers greater than 650 should not be trusted
because the diameter of the indentation is too small to
be measured accurately and the ball penetrator may
flatten out.
 Rules of thumb
3000 kg load should be used for a BHN of 150 and above
1500 kg load should be used for a BHN between 75 and 300
 500 kg load should be used for a BHN less than 100
The material’s thickness should not be less than 10 times the
depth of the indentation
By Aragaw G. 144

Advantages & Disadvantages of the
Brinell Hardness Test
 Advantages
Well known throughout industry with well accepted
results
Tests are run quickly (within 2 minutes)
Test inexpensive to run once the machine is purchased
Insensitive to imperfections (hard spot or crater) in the
material
 Limitations
Not well adapted for very hard materials, where in the
ball deforms excessively
Not well adapted for thin pieces
Not well adapted for case-hardened materials
Heavy and more expensive than other tests.
By Aragaw G. 145

II. Vickers hardness test
 The Vickers hardness was Developed in 1922 and first
introduced in England in 1925 by R. Smith and G. Sandland.
 It was originally known as the 136° diamond pyramid
hardness test because of the shape of the indenter.
 The manufacture of the first tester was a company known
as Vickers-Armstrong Limited, of Cray ford, Kent, England.
 As the test and the tester gained popularity, the name Vickers
became the recognized designation for the test.
 The Vickers test method is similar to the Brinell principle in
that a defined shaped indenter is pressed into a material, the
indenting force is removed, the resulting indentation
diagonals are measured, and the hardness number is
calculated by dividing the force by the surface area of the
indentation.
By Aragaw G. 146

Vickers Test (cont….)
 Comparable to Brinell
Test except using a
pyramid shaped
diamond to make
indentation.
 Lighter loads than
Brinell Test
◦ From 1 to 120 kg
By Aragaw G. 147

 TheVickers hardness number (formerly known as DPH for
diamond pyramid hardness) is a number related to the
applied force and the surface area of the measured
unrecovered indentation produced by a square-base
pyramidal diamond indenter.
 TheVickers indenter has included face angles of 136° (Fig.
21), and theVickers hardness number (HV) is computed
from the following equation:
 where P is the indentation load in kgf, and d is the
mean diagonal of indentation, in mm.
By Aragaw G.
148

 The calculation ofVickers hardness can be done directly
from this formula or from Tables.
 For example, if the average measured diagonal length,
d, is 0.0753 mm with a 1 kgf load, then theVickers
number is:
By Aragaw G.
149
Fig. 21

Advantage and Disadvantages of theVickers test
 Advantages of theVickers test are:
 Vickers hardness, in general, is independent of force when
determined on homogeneous material, except possibly at forces
below 5 kgf.
The edge or ends of the diagonals are usually well defined for
measurement.
The indentations are geometrically similar, irrespective of size.
One continuous scale is used for a given force, from lowest to
highest values.
Indenter deformation is negligible on hard material.
 Disadvantages of theVickers test are:
Test is slow and not well adapted for routine testing.Typical test and
measurement times are in the one- minute range.
 Careful surface preparation of the specimen is necessary, especially
for shallow indentations.
Measurement of diagonals is operator dependent, with possible
eyestrain and fatigue adding to test errors.
By Aragaw G. 150

III. RockwellTest
 Was Invented by S. P. Rockwell in 1922
 Test measures depth rather than diameter of indentation.
 1200 Diamond indenter presses against surface with minor load
and then major load.
 The difference in depths of penetration is a measure of the
hardness of material.
 The Rockwell hardness test is somewhat similar to the Brinell
hardness test, but there is a significant difference in the equipment.
 The Rockwell system uses indenters (1/8-in, ball, 1/16-in. ball and a
diamond cone with 1200 face angle) and load values of a
combination obtainable with 40-, 50-, and 60-kg. weights.
By Aragaw G. 151

RockwellTest(cont…..)
 The Rockwell testing machine operates
somewhat like a press, using a indenter
to penetrate the surface of the test
sample.
 The depth of the indentation
determines the materials hardness on a
scale of 0-100
By Aragaw G. 152

By Aragaw G. 153
Typical anvils for Rockwell
hardness testing

RockwellTest Description
 Specially designed machine that applies load through a
system of weights and levers
Indenter can be 1/16 in hardened steel ball, 1/8 in steel
ball, or 120° diamond cone with a somewhat rounded
point (brale)
Hardness number is an arbitrary value that is inversely
related to the depth of indentation
Scale used is a function of load applied and the indenter
• Rockwell B- 1/16in ball with a 100 kg load
• Rockwell C- Brale is used with the 150 kg load
 Operation
Minor load is applied (10 kg) to set the indenter in
material
Dial is set and the major load applied (60 to 100 kg)
Hardness reading is measured
Rockwell hardness includes the value and the scale letter
By Aragaw G. 154

Rockwell Hardness(cont…..)
By Aragaw G. 155
 The Rockwell Hardness test is a hardness measurement
based on the net increase in depth of impression as a load is
applied.
 Hardness numbers have no units and are commonly given in
the R, L, M, E and K scales. *******
 The higher the number in each of the scales means the
harder the material.

RockwellValues
 B Scale: Materials of medium hardness (0 to 100HRB) Most
Common
 C Scale: Materials of harder materials (> 100HRB) Most Common
 Rockwell scales divided into 100 divisions with each division
(point of hardness) equal to 0.002mm in indentation.Thus
difference between a HRB51 and HRB54 is 3 x 0.002 mm - 0.006
mm indentation
 The higher the number the harder the number
Scale Indenter Applied Load (kg)
A Brale 60
B 1/16 in 100
C Brale 150
D Brale 100
E 1/8 in 100
F 1/16 in 60
G 1/16 in 150
By Aragaw G. 156

Rockwell hardness number
 The Rockwell hardness number is given by:
Rockwell hardness = E - h
 Where; h is penetration depth, E is a constant
determined by the form of the indenter; for a
diamond cone indenter E is 100, for a steel ball 130
(BS 891: Rockwell Hardness Test; BS 4175: Rockwell
Superficial Hardness Test).
By Aragaw G. 157

Advantages Rockwell testing
 Rockwell testing has two important advantages as
compared to other tests previously discussed:
1. Application and retention of the minor load during
the test prepares the surface upon which the
incremental penetration depth due to the major load is
measured.
2. The hardness value is read directly on the dial gage
without the necessity for measuring the indentation
dimensions, as in other hardness testing methods.
This expedites the testing process—an important
advantage in manufacturing and quality control.
By Aragaw G. 159

By Aragaw G.
Hardness-testing
Methods
and
Formulas
Figure 2.12 General characteristics of hardness-testing
methods and formulas for calculating hardness.
160

4.1.2. Spark Testing
 The shape and
characteristic of sparks
created when metal is
ground will help
determine its properties.
 IE: carbon steel , mild
steel.
 This section is discussed
in detail in LO-1 slide no.
44-46****
By Aragaw G. 161

By Aragaw G. 162
4.1.3.Tensile StrengthTesting

4.1.3.Tensile StrengthTesting
 The Tensile test is one of the most widely
accepted means of obtaining valid data
about the mechanical properties of a metal.
 “Tensile” is a test in which a prepared
sample is pulled until the sample breaks.
 Test Measurements are recorded in PSI
(Pounds per Square Inch) E7018 = 70,000 PSITensile
 Test samples called “Tensile Bolts” can
reveal aTensile strength, Elastic limit,Yield
point, and Ductility.
By Aragaw G. 163

TensileTesting(cont……)
 Standard tensile specimens are round or
rectangular in cross section with a carefully
prepared center section.
 A selected distance in the center is then
marked for the gage length (Fig. below)
By Aragaw G. 164
Figure 8.1 typical dimensions of tensile testing specimen.

By Aragaw G. 165
Specimen
Machines
Tensile-test Specimen and Machine

Microstructure of Fracture in
Metals
Formation of voids in the necked region during tensile testing,
leading to fracture.
By Aragaw G. 166

 The specimen is given a gage length mark and
mounted in the tensile grips.
 The tensile machine is adjusted for the test.
 Adjustments include selection of load range, rate
of loading, and magnification of extension.
 Usually a recorder plots the behavior of the test
piece by indicating stress in pounds and strain in
inches.
 Stress will be directly proportional to strain
while the material is exhibiting elastic behavior.
 If the load were to be released while in the
elastic range, the material would regain its
original length. By Aragaw G. 167

By Aragaw G. 168
Figure
8.2
shows
the
offset
method
to
determine
yield
load.

Figure 8.2 shows the offset method to determine
yield load.
 Offset (A to C) is determined by a percentage of
the gage length, usually 0.2% of the gage length.
 Line A-X has been made by machine recorder.
 Point X is the yield point.
 The operator computes offset and locates point
C.
 Line C-D is constructed. Point D (intersection) is
projected to the left to stress line which is the
yield load.
By Aragaw G. 169

 As more load is applied, the metal will start to
elongate and show little increase in load capacity.
 This is called the zone of plastic deformation.
 During plastic deformation the metal will tend to
work harden.
 Some metals elongate rapidly near maximum load.
 This elongation reduces the cross sectional area.
 During the process of elongation on a permanent
basis, the metal is becoming smaller but stronger.
 The load indicator may even indicate a lower load
while this is happening.
By Aragaw G. 170

By Aragaw G. 171

 Later, the load indicator reaches
a maximum value and drops
slowly to a point where failure
occurs.
 The fracture load is usually much
lower than the maximum load
when testing ductile metals.
 After fracture has caused a
complete separation, the
specimen is taken from the
machine.
 One of the parts is measured
across the face of the fracture to
obtain final dimensions.
 From the final dimensions the
final area is computed.
By Aragaw G. 172
Engineering strain (For compression test)
e = (A – Ao)/Ao = d/Ao

 At this time the two parts are fitted back together
and the final gage length is measured.
 A typical report on the tensile test includes the
yield strength, tensile strength, ductility, and
modulus of elasticity.
Figure 8.3 typical cup-cone fracture
of ductile material
By Aragaw G. 173

Tensile Strength. Tensile strength is found by dividing the
maximum load by the original area.
The formula is written as
WhereTS =Tensile strength
Lm = Load at maximum value
Ao = Area original
To better understand the formula, work the following
problem:
Given: Load at maximum value is 200,000N,Area
= 100mm2
Find:Tensile strength
o
m
A
L
TS 
By Aragaw G. 174

Ductility. Ductility is found by two methods.
 One is based on the change in length, and the
other is based on the change in area.
 To find percent elongation use the formula,
By Aragaw G. 175
% of elongation %e = (A – Ao)/Ao X 100;
were:A=final area,
Ao= original area

Modulus of Elasticity. The modulus of elasticity is
determined by dividing stress by strain.
 Remember that when the item calls for strain (in./in.), this
means inches of elongation divided by the gage length.
 Thus, modulus of elasticity is merely a ratio of stress to
strain.
 Some designers consider the numerical value of modulus
of elasticity as a factor of how rigid a material will be
when subjected to a load.
 The modulus of elasticity value depends on what the
material is made of more than how strong or hard it is.
By Aragaw G. 176
e
E


,
Elasticity
of
Modulus

Important Mechanical Properties from a
TensileTest
 Young's Modulus: This is the slope
of the linear portion of the stress-
strain curve, it is usually specific to
each material; a constant, known
value.
 Yield Strength: This is the value of
stress at the yield point, calculated
by plotting young's modulus at a
specified percent of offset (usually
offset = 0.2%).
 UltimateTensile Strength: This
is the highest value of stress on the
stress-strain curve.
 Percent Elongation: This is the
change in gauge length divided by
the original gauge length.
By Aragaw G. 177

 The Elastic Limit (Elastic deformation) of metal
is the stress (load) it can withstand and still
return to the original length after the load is
released.
 Yield Strength(plastic deformation) occurs
when the test sample stretches however
will not return to its original length.
 Ductility is the ability of a metal to stretch or
elongate before it breaks.
By Aragaw G. 178
Important Mechanical Properties from a
TensileTest

F
d
bonds
stretch
return to
initial
1. Initial 2. Small load 3. Unload
Elastic means reversible.
Elastic Deformation
By Aragaw G. 179

1. Initial 2. Small load 3. Unload
Plastic means permanent.
F
d
linear
elastic
linear
elastic
dplastic
Plastic Deformation (Metals)
By Aragaw G. 180

By Aragaw G.
Formulas used in Tensile-testing
Figure (a) A standard tensile-test specimen
before and after pulling, showing original and
final gage lengths.
(b) A tensile-test sequence showing different
stages in the elongation of the specimen.












o
o
o
o
l
l
A
P
e
E
l
l
l
e
A
P
ln
=
strain,
True
=
stress,
True
,
Elasticity
of
Modulus
Strain,
g
Engineerin
Stess,
g
Engineerin




181

Exercise 1. An aluminum rod, 1500mm long,
with a diameter of 10mm is held vertically
and loaded with 2000N weight. If the road
stretches 2mm, calculate,
a) the stress (σ)
b) the strain (ε)
c) the modulus of elasticity (E).
d) percentage of elongation(%E)
By Aragaw G. 182

4.1.4 Impact Testing
 An Impact tester uses a heavy pendulum that is able to
measure the amount of force required to shear or
fracture a test sample .
 Impact testing may be performed using either the Izod
or Charpy method. (Both methods are similar)
 Fracture behavior depends on many external factors:
 Strain rate
 Temperature
 Stress rate
 Impact testing is used to ascertain the fracture
characteristics of materials at a high strain rate and a
tri-axial stress state.
By Aragaw G. 183

Impact Testing
 A Charpy or Izod test measures the ability to
withstand an Impact force.
 Low Charpy test readings indicate brittle weld
metal
 Higher Charpy readings indicate the samples
toughness.
 In an impact test, a notched specimen is
fractured by an impact blow, and the energy
absorbed(Ef) during the fracture is measured.
By Aragaw G. 184

I. Izod test
 Strikes at 167 Joules.
 Test specimen is held
vertically.
 Notch faces striker.
By Aragaw G. 185

II. Charpy impact test
 Strikes form higher
position with 300 Joules.
 Test specimen is held
horizontally.
 Notch faces away form
striker.
By Aragaw G. 186

Impact Test: Examples
Calculate the amount
of energy absorbed in
the impact test is the
mass of the hammer is
200Newton, ho=.75m,
hf=.20m
By Aragaw G. 187

4.2. Specimen preparation for
testing
 Specimen is an individual animal, plant, object, etc.
used as an example of its species or type for
scientific study or display. Or
 it is an example of something regarded as typical
of its class or group:
By Aragaw G. 188
Specimen for tensile testing

Spacemen for Impact testing
 Fig. 5 Dimensional details of Charpy
test specimens most commonly used
for evaluation of notch toughness.
◦ (a)V-notch specimen (ASTM E 23
and ISO 148).
◦ (b) Keyhole specimen (ASTM E 23).
◦ (c) U-notch specimen (ASTM E 23
and ISO 83)
By Aragaw G. 189

5.1. Recording and reporting results of
material tests
 To record the test results of material test we
need to write the following guiding points:
The type of the test.
The aim of the test.
The principle (method) of the test
The apparatus which is going to be used.
Preparation and number specimens to be tested.
 The procedure of the test.
The interpretation of the results
By Aragaw G. 190
LO-5:- Record and report
results of material test

CONT………..
5.2. REPORTING OF RESULTS
 The following information should be included in
the report on each test specimen:
 Identification mark, Date of test, Age of specimen
 Curing conditions, including date of manufacture of
specimen
 Weight of specimen, Dimensions of specimen
 Cross-sectional area, Maximum load
 The property tested
 Appearance of fractured faces of concrete and type
of Fracture, (for mechanical tests).
By Aragaw G. 191

TensileTesting
 Uses an extensometer to apply measured
force to a test specimen.
 The amount of extension can be measured
and graphed.
 Variables such as strain, stress, elasticity,
tensile strength, ductility and shear
strength can be gauged.
 Test specimens can be round or flat.
By Aragaw G. 192
CONT………..

By Aragaw G. 194
Producing graphs
Two basic graphs:
 Load – extension graph.
 Stress – strain graph.

Load - extension graph for low carbon steel
By Aragaw G. 195

Draw graph for this tensile test?
By Aragaw G. 197
Identify the straight
line part of the graph.

Young's Modulus (E) & Tensile
Strength
 E = Stress
Strain
 Stress = Load
Cross section area
 Strain = Extension
Original length
 Tensile strength = Maximum Load
Cross section area
 Maximum load is the highest point on the graph.
Often called UltimateTensile Strength (UTS)
By Aragaw G. 198

Example:-Young's Modulus for Load
–extension graph
By Aragaw G. 199
Tensile strength = Maximum Load = 142 = 1.8KN/mm2
Cross section area 78.55
So that the Ultimate Tensile Strength (UTS) = 1.8KN/mm2

Assisting in Material Testing: Identifying Engineering Materials

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