This document discusses various materials testing methods. It describes mechanical properties testing which involves destructive testing of specimens to determine properties like strength, ductility, and toughness. Common destructive tests mentioned are hardness tests and impact tests like the Charpy and Izod tests. Non-destructive testing methods discussed include dye penetration, magnetic particle, ultrasonic, and radiographic testing. Specific hardness tests covered are Rockwell, Brinell, Vickers, and Shore hardness tests.

1. CHAPTER 4
Materials Testing

2. Materials Testing
•Mechanical properties are obtained by mechanical
testing.
•Mechanical testing is used for developing design data,
maintaining quality control, assisting in alloy development
programs and providing data in failure analysis.

3.  Mechanical testing is usually destructive and requires test
specimens of the material to be machined or cut to the
specific shape required by the test method.
cont,.

4.  Describe material when a force is applied to it.
 Determined through testing, usually involving
destruction of material.
 Extremely important to consider in design.
Mechanical Properties

5. a) Ductility
b) Toughness
c) Brittleness
d) Hardness
e) Plasticity
f) Elasticity
g) Strength
Types of mechanical properties

6.  Ductility is a solid material's ability to deform under
tensile stress; this is often characterized by the
material's ability to be stretched into a wire.
Ductility

7. Tensile test of an
AlMgSi alloy
The local necking and the cup and
cone fracture surfaces are typical for
ductile metals.

8. Schematic appearance
of round metal bars
after tensile testing.
a) Brittle fracture
b) Ductile fracture
c) Completely ductile fracture

9. Toughness
•Toughness is the ability of a material to absorb energy and
plastically deform without fracturing
• Material toughness is defined as the amount of energy per
volume that a material can absorb before rupturing.
• It is also defined as the resistance to fracture of a material when
stressed.
•Toughness requires a balance of strength and ductility.

10.  A material is brittle if, when subjected to stress, it breaks
without significant deformation (strain).
 Brittle materials absorb relatively little energy prior to
fracture, even those of high strength.
 Breaking is often accompanied by a snapping sound. Brittle
materials include most ceramics and glasses (which do not
deform plastically) and some polymers, such as PMMA and
polystyrene.
 Many steels become brittle at low temperatures (see
ductile-brittle transition temperature), depending on their
composition and processing.
Brittleness

11. Brittle fracture in cast iron tensile test
pieces

12. Graph comparing stress-strain curves
for ductile and brittle materials.

13.  Hardness is the degree of resistance to indentation,
penetration, abrasion and wear.
 Indentation hardness measures the resistance of a sample
to permanent plastic deformation due to a constant
compression load from a sharp object; they are primarily
used in engineering and metallurgy fields. The tests work
on the basic premise of measuring the critical dimensions
of an indentation left by a specifically dimensioned and
loaded indenter.
 Common indentation hardness scales are Rockwell,
Vickers, Shore, and Brinell.
Hardness

14.  Plasticity is the propensity of a material to undergo
permanent deformation under load.
Plasticity

15.  Elasticity (or stretchiness) is the physical property of
a material that returns to its original shape after the
stress (e.g. external forces) that made it deform or
distort is removed. The relative amount of
deformation is called the strain.
Elasticity

16.  Strength is the ability of a material to withstand
various loads to which it is subjected during a test or
service.
Strength

17.  2 types of materials testing:
a) Destructive test
-results in the part being destroyed during the
quality control testing program.
b) Non destructive test
- is done in such a manner that the usefulness of the
product or part is not damaged or destroyed.
Materials Testing

18.  Non destructive inspection techniques enable
inspectors to check properties critical to the safe
performance of metal parts without causing damage
to the parts themselves.
 This test is concerned with testing for cracks and
flaws
Non Destructive Test

19. a) Dye penentrant test
b) Radiographic test
c) Magnetic particle test
d) Ultrasonic test
Types of non destructive test

20.  It is easy to use and economical.
1) The specimen is coated with a red liquid dye which
soaks into the surface crack or flaw.
2) The liquid is then washed off and the part dried.
3) A developer is dusted or sprayed on the part.
4) Flaws and cracks show up red against the white
background of the developer.
Dye Penentrant Test

21. Cracks in a weld

22.  This test involves passing gamma rays (X-rays)
through a part and onto sensitive film to detect flaws
in the metal.
 The developed film has an image of the internal
structure of the part.
 A defect will show up on the film as a dark area.
 X-rays are very sensitive and are capable of inspection
any thickness of almost any kind of materials.
Radiographic test

23.  This test is used to detect flaws on or near the surface of
iron-based metals.
1) The part is first magnetized.
2) It is then either dusted with fine iron powder or coated
with a solution in which iron particles are suspended.
3) Flaws in the workpiece cause the lines of magnetic force
to become distorted and break through the surface.
4) There they attract concentrations of the iron particles,
which reveal defects in the metal.
Magnetic particle test

24.  The limitations of this technique are apparent when
the flaw is parallel to the lines of magnetic force.
 The flaw will not interrupt the force and no indication
of it will appear when magnetic particles are applied.
Cont.

25. Concentration of the iron particle
shows defect in the metal

26.  This test use ultasonic sound waves to detect cracks
and flaws in almost any material that can conduct
sound.
 Sound waves can also be used to measure the
thickness from one side of the material.
Ultrasonic test

27.  The human ear can hear sound waves with
frequencies ranging from 20 to 20,000 Hertz.
 Sound waves that vibrate with a frequency greater
than 20,000 Hz are inaudible and are called ultrasonic.
Cont.

28.  These high frequency sound waves are produced by a
piezoelectric transducer.
 The transducer is electrically pulsed and then vibrates
at its own natural frequency.
1) In order to operate, the transducer must be joined to
the piece being tested by a liquid coupling such as a
film of oil, glycerin or water.
Cont.

29. 2) The high frequency sound waves are transmitted
through the material.
3) The flaws reflect the sound waves and are detected
on an oscilloscope.
There is no size limitation on work that can be
tested by ultrasonic test.
Cont.

30. Ultrasonic Test

31. DESTRUCTIVE TEST

32. • Destructive testing is a costly and time consuming
technique. A specimen is selected at random from a
large number of pieces.
• Two types of destructive test:
a) Hardness test
b) Impact test
Destructive Testing

33. • 2 types of impact test:
a) Charpy impact test
b) Izod impact test
Impact Test

35. The Charpy specimen has a
square cross section
(10mm x 10mm) and
contains a 45C V notch, 2
mm deep with a 0.25 mm
root radius.
Charpy Impact Test

36. •The specimen is supported
as a beam in a horizontal
position and loaded behind
the notch by the impact of a
heavy swinging pendulum.
•The specimen is forced to
bend and fracture at a high
strain rate of the order 103 s-1.

37. Method of loading in
Charpy and Izod tests.

38.  Impact Testing Equipment
 Izod and Charpy are the most common tests.
 Both employ a swinging pendulum and conducted on small notched
specimens. The notch concentrated the load at a point causing failure.
Other wise without the notch the specimen will plastically deform
throughout.
 They are different in the design of the test specimen and the velocity at
which the pendulum strikes the specimen.
 Charpy: the specimen is supported as a single beam and held horizontally.
Impacted at the back face of the specimen.
 Izod: the specimen is supported as a cantilever and help vertically.
Impacted at front face of the specimen.
Equipment

39.  The energy absorbed in fracturing the specimen.
 After breaking the test bar, the pendulum rebounds
to a height which decreases as the energy absorbed
in fracture increases.
 The energy absorbed in fracture, usually expressed in
joules, is rending directly from a calibrated dial on the
impact tester.
The principal measurement

40. • Indentation hardness measures the resistance of a
sample to permanent plastic deformation due to a
constant compression load from a sharp object.
• 4 types of hardness test:
a) Rockwell
b) Brinell
c) Vickers
d) Shore
Hardness Test

41.  The Rockwell hardness tester functions according to
the depth of penetration made in metal by a specific
kind of penetrator point forced by a given load.
Rockwell Hardness Test

42. Various Rockwell Scales

43.  The determination of the Rockwell hardness of a
material involves the application of a minor load
followed by a major load, and then noting the depth
of penetration.
 The hardness value directly taken from a dial, in which
a harder material gives a higher number.
Operation

44. Rockwell Hardness Tester

45.  The Rockwell hardness test uses two loads that are applied
sequentially.
 A minor load of 10 kg is applied that helps seat the indenter
and remove the effect of surface irregularities.
 A major load which varies from 60 kg to 150 kg is then
applied.
 The difference in depth of indentation between the major
and minor loads provides the Rockwell hardness number.
 This number is taken directly from the dial on the machine.
Cont.

46.  To get a reliable reading the thickness of the test
piece should be at least 10 times the depth of the
indentation.
 The superficial Rockwell scales use lower loads and
shallower impressions on brittle and very thin
materials.
Cont.

47.  1) its ability to display hardness values directly, thus
obviating tedious calculations involved in other
hardness measurement techniques.
 2) typically used in engineering and metallurgy
because of its speed, reliability, robustness,
resolution and small area of indentation.
Advantages

48.  Brinell hardness test use a machine to press a 10 mm
diameter, hardened steel ball into the surface of the
test specimen.
 This machine applies a load for a specific period of
time and causes an indentation that is used to
calculate hardness.
Brinell Hardness Tester

49. Cont.

50.  The load applied to the steel ball depends on the type
of metal under test.
 The load is usually applied for 10 to 15 seconds.
 The diameter of the indentation is measured to ±0.5
mm using a low magnification portable microscope.
Cont.

51. The Brinell hardness number is found by measuring the
diameter of the indentation and then finding the hardness
number on a calibrated chart.

52.  The Vickers hardness test is similar in principle to the
Brinell hardness test.
 The major difference is that the indenter in the
Vickers hardness test is a 136 square base diamond
cone.
 The load varies from 1 kg to 120 kg.
Vickers Hardness Tester

53.  The specimen is placed on an anvil and raised by a
screw until it is close to the point of the indenter.
 The starting lever is tripped, allowing the load to be
slowly applied to the indenter.
 The load is released, the anvil lowered and a filar
microscope is swung over to measure the diagonals
of the square indentation to ±0.001 mm.
 Diagonal measurements are averaged and the
Vickers hardness number is followed by the letters
HV.
Procedure

54.  Extremely accurate readings can be taken.
 one type of indenter covers all types of metals and
surface treatment.
Advantages

55.  An instrument that uses a test specimen that is freely
supported horizontally and a glass tube that contains
a diamond tipped hammer positioned vertically over
the specimen.
 The hammer is allowed to fall from a set height and
the height of rebound is measured.
 The test shows that the higher the rebound, the
harder the specimen.
Shore Scleroscope Hardness Tester

56. Shore Scleroscope