Material Testing

1. Material Testing
Group 2:
John Kevin Lagundino
Dexter Jay Pacultad
Heracleo Amoc Jr.

2. Material Testing
measurement of the characteristics and
behavior of such substances as metals,
ceramics, or plastics under various
conditions. The data thus obtained can be
used in specifying the suitability of
materials for various applications—e.g.,
building or aircraft construction,
machinery, or packing.

3. Why are metals tested ?
• Ensure quality
• Test properties
• Prevent failure in use
• Make informed choices in using materials
Factor of Safety
is the ratio comparing the actual
stress on a material and the safe
useable stress.

4. Two forms of testing
• Mechanical tests – the material may be
physically tested to destruction. Will
normally specify a value for properties
such as strength, hardness, toughness,etc
• Non-destructive tests (NDT) – samples or
finished articles are tested before being
used.

5. Types of Testing
Mechanical testing:
• Tensile
• Creep
• Compression
• Bend or flexure
• Hardness
• Impact
• Fatigue
Non-destructive
tests:
•Magnetic
•Dyes
•Ultrasound

6. Tensile Testing
 also known as tension testing,is a
fundamental materials science test in
which a sample is subjected to a
controlled tension until failure. The results
from the test are commonly used to select
a material for an application, for quality
control, and to predict how a material will
react under other types of forces.

7. Tensile Testing
 Properties that are directly measured via
a tensile test are ultimate tensile strength,
maximum elongation and reduction in
area.From these measurements the
following properties can also be
determined: Young's modulus, Poisson's
ratio, yield strength, and strain-hardening
characteristics.

8. Tensile Testing
Tensile Testing Machine

9. Tensile specimen
Tensile Testing
Tensile specimens made from an
aluminum alloy. The left two
specimens have a round cross-
section and threaded shoulders. The
right two are flat specimen designed
to be used with serrated grips.
A tensile specimen is a
standardized sample
cross-section. It has two
shoulders and a gauge
(section) in between. The
shoulders are large so they
can be readily gripped,
whereas the gauge section
has a smaller cross-section
so that the deformation
and failure can occur in
this area.

10. Tensile Testing
A standard specimen is prepared in a round or a square section along
the gauge length, depending on the standard used. Both ends of the
specimens should have sufficient length and a surface condition such
that they are firmly gripped during testing.

11. The shoulders of the test specimen can be
manufactured in various ways to mate to various
grips in the testing machine (see the image
below). Each system has advantages and
disadvantages; for example, shoulders designed
for serrated grips are easy and cheap to
manufacture, but the alignment of the specimen
is dependent on the skill of the technician. On
the other hand, a pinned grip assures good
alignment. Threaded shoulders and grips also
assure good alignment, but the technician must
know to thread each shoulder into the grip at
least one diameter's length, otherwise the
threads can strip before the specimen fractures.
Tensile Testing

12. Tensile Testing
A. A Threaded shoulder for use with a threaded grip
B. A round shoulder for use with serrated grips
C. A butt end shoulder for use with a split collar
D. A flat shoulder for used with serrated grips
E. A flat shoulder with a through hole for a pinned grip

14. CreepTesting
Creep Testing
A creep-testing machine measures the Creep (the
tendency of a material after being subjected to high
levels of stress, e.g. high temperatures, to change
its form in relation to time) of an object. It is a device
that measures the alteration of a material after it has
been put through different forms of stress. Creep
machines are important to see how much strain
(load) an object can handle under pressure, so
engineers and researchers are able to determine
what materials to use.

15. • The device generates a creep time-
dependent curve by calculating the steady
rate of creep in reference to the time it
takes for the material to change. Creep
machines are primarily used by engineers
to determine the stability of a material and
its behaviour when it is put through
ordinary stresses.
CreepTesting

16. Design
• Researchers look to test objects with a
creep machine to understand the process
of metallurgy and the physical mechanical
properties of a metal, test the development
of alloys, receive data from the loads that
are derived and to find out whether a
sample or material is within the boundary
of what they are testing. The basic design
of a creep machine is the furnace, loading
device and support structure.
CreepTesting

17. • Load platform or sometimes called load hanger is
where the object will endure pressure at a constant
rate.
• Grips are used to hold the material you are testing
in a certain position. Position is important because if
the alignment is off, the machine will deliver
inaccurate readings of the creep of the material.
• Dial Gauge is used to measure the strain. It is the
object that captures the movement of the object in
the machine. The load beam transfers the
movement from the grip to the dial gauge.
• Heating Chamber is what surrounds the object and
maintain the temperature that the object is subjected
to.
CreepTesting

18. Applications
• Creep machines are most commonly used
in experiments to determine how efficient
and stable a material is. The machine is
used by students and companies to create
a creep curve on how much pressure and
stress a material can handle. The machine
is able to calculate the stress rate, time
and pressure.
CreepTesting

19. Applications
• Displacement-Limited applications : the size must
be precise and there must be little errors or
tendency to change.This is most commonly found in
turbine rotors in jet engines.
• Rupture Limited applications: in this application
the break cannot occur to the material but there can
be various dimensions as the material goes through
creep. High pressure tubes are examples of them.
• Stress relaxation limited application : the tension
at the beginning becomes more relaxed and the
tension will continue to relax as the time goes by,
such as cable wires and bolts.
CreepTesting

21. Compressive Testing
• determine a material’s response to crushing, or
support-type loading (such as in the beams of a
house). Testing machines and extensometers
for compression tests resemble those used for
tension tests. Specimens are generally simpler,
however, because gripping is not usually a
problem. Furthermore, specimens may have a
constant cross-sectional area throughout their
full length. The gauge length of a sample in a
compression test is its full length.

23. Bend Test
 Bend test - Application of a force to the center
of a bar that is supported on each end to
determine the resistance of the material to a
static or slowly applied load.
 Flexural strength or modulus of rupture -
The stress required to fracture a specimen in a
bend test.
 Flexural modulus - The modulus of elasticity
calculated from the results of a bend test, giving
the slope of the stress-deflection curve.

24. (c)2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under
license.
(a) The bend test often used for measuring the strength ,
and (b) the deflection δ obtained by bending

25. 25
• Schematic for a 3-
point bending test.
• Able to measure the
stress-strain behavior
and flexural strength
of brittle ceramics.
• Flexural strength
(modulus of rupture or
bend strength) is the
stress at fracture.
Flexural Strength
See Table 7.2 for more values.

27. Hardness of Materials
Is the measure of the resistance of a metal to
permanent plastic deformation. The hardness of a
metal is measured by forcing an indenter into its
surface. The indenter material which is usually a
ball, pyramid, or cone is made of a material much
harder than the material being tested.

28. 28
Hardness Testers

29. Hardness testing machine
The indenter is
pressed into the metal
Softer materials leave
a deeper indentation

31. Brinell hardness test
•Uses ball indentor.
•Cannot be used for
thin materials.
•Ball may deform on
very hard materials
•Surface area of
indentation is
measured.

33. Vickers hardness test
• Uses square
pyramid indentor.
• Accurate results.
• Measures length of
diagonal on
indentation.

35. Rockwell hardness tests
• Gives direct reading.
• Rockwell B (ball) used
for soft materials.
• Rockwell C (cone) uses
diamond cone for hard
materials.
• Flexible, quick and
easy to use.

37. Impact Tests
• Toughness of metals is the ability to
withstand shock load and impact. It will not
fracture when twisted.

39. Izod test
• Strikes at 167 Joules.
• Test specimen is held
vertically.
• Notch faces striker.

41. Charpy impact test
• Strikes form higher
position with 300
Joules.
• Test specimen is held
horizontally.
• Notch faces away form
striker.

43. Fatigue
• Fatigue is due to the repeated loading and unloading.
• When a material is subjected to a force acting in different
directions at different times it can cause cracking. In time this
causes the material to fail at a load that is much less than its
tensile strength, this is fatigue failure. Vibration for example is a
serious cause of fatigue failure.
• Fatigue can be prevented with good design practice.
1. A smooth surface finish reduces the chance of surface cracking.
2. Sharp corners should be avoided.
3. Corrosion should be avoided as this can cause fatigue cracks.

45. Non-destructive testing (NDT)

46. Why use NDT?
• Components are not destroyed
• Can test for internal flaws
• Useful for valuable components
• Can test components that are in use

48. Penetrant testing
• Used for surface flaws.
• The oil and chalk test is a traditional
version of this type of testing. Coloured
dyes are now used.

51. Magnetic particle testing
• Used for ferrous metals.
• Detects flaws close to the surface of the material.
• The component to be tested must first be
magnetized.
• Magnetic particles which can be dry or in solution
are sprinkled onto the test piece.
• The particles stick to the magnetic field and flaws
can be inspected visually by examining the pattern
to see if it has been distorted.
• The component must be demagnetized after testing.

54. Eddy current testing
• Used for non-ferrous metals
• A.C. current is passed through the coil.
• The test piece is passed under the coil
causing secondary currents called eddy
currents to flow through the test piece.
This causes a magnetic field to flow in
the test piece.
• The flaws are detected on an
oscilloscope by measuring a change in
the magnetic field.

56. Ultrasonic testing
Ultrasonic Sound waves are bounced off the component
and back to a receiver. If there is a change in the time
taken for the wave to return this will show a flaw. This is
similar to the operation of a sonar on a ship.
Operation.
1. The ultrasonic probe sends the sound wave through the
piece.
2. The sound wave bounces of the piece and returns.
3. The results are then placed on the display screen in the
form of peaks.
4. Where the peaks fluctuate this will show a fault in the
piece.
Uses.
• This is generally used to find internal flaws in large
forgings, castings and in weld inspections.

59. Thanks for Watching!
• THE END!