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LABORATORY MANUAL FOR HARDNESS TEST
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LABORATORY MANUAL FOR HARDNESS TEST
Department of Materials Science and Engineering,
African University of Science and Technology, Abuja.
A) ROCKWELL HARDNESS TEST
(I) Aim: To determine the Rockwell hardness number of the given Specimen using
“Rockwell Hardness tester”.
(II) Apparatus:

Rockwell hardness testing machine.

Diamond cone indentor, ball indentor.

Specimens (Hardened steel, Mild steel, Brass, Copper, Aluminium)
(III) Theory: Hardness of a material is generally defined as Resistance to the permanent
indentation under static and dynamic load. Hardness is the property of the material by
which it offers resistance to scratch or indentation. It is the most important property, as
the material is subjected to friction and scratch. When a material is required to use under
direct static or dynamic loads, only indentation hardness test will be useful to find out
resistance to indentation. This test is an indentation test used for smaller specimens and
harder materials. In this test indentor is forced into the surface of a test piece in two
operations, measuring the permanent increase in depth of an indentation from the depth
increased from the depth reached under a datum load due to an additional load.
Measurement of indentation is made after removing the additional load. Indentor used is
the cone having an angle of 120 degrees made of black diamond. The principle of
Rockwell hardness test has to do with the application of a standard load (Based on the
type of material) through a standard indentor (cone or ball indentor) for a standard
duration of time. The hardness number is directly obtained in the experiment.
The Rockwell hardness is derived from the measurement of the depth of the impression
EP = Depth of penetration due to Minor load of 98.07 N.
Ea = Increase in depth of penetration due to Major load.
E = Permanent increase of depth of indentation under minor load at 98.07 N even after
removal of Major load.
Suitable Application:



Rockwell hardness test is generally used for larger sample geometries.
It is a ‘quick test’ mainly used for metallic materials.
It can also be used for advanced tests, such as the Jominy (end quench) test
(HRC).
(IV) Equipment Description:
Figure 1: Rockwell hardness testing machine.
(V) Procedure:
a) Keep the loading and unloading lever at position “A” which is unloading position.
b) Select suitable indentor & weights according to the scale.
c) Place the specimen on testing table anvil.
d) Turn the hand wheel to raise a job until it makes contact with indentor & continue
turning till the longer pointer at the dial gauge makes 2 ½ rotations. Then it stops at zero
continue turning slowly till the small pointer reaches the red spot at 3‟, this is automatic
zero setting dial gauge.
e) Turn the lever position “A” to “B” i.e. from unloading to the loading position. So that the
total load will act.
f) When the longer pointer of the dial gauge reaches steady position, take back the lever
to the unloading position “A”. [Avoid sudden release at the lever]
g) Now note down the reading in the last dial indicator by notifying the large pointer
h) Turn back the hand wheel and remove the job.
i) Similarly, repeat the step from ‘a-h’ for different trials and for different metals.
(VI) Observation and Calculation:
Type of
specimen
Hard Metals
Type of
Indentor
Diamond cone
Soft Metals
Ball (1/16”)
S/No
Specimen
01
02
03
04
05
Hardened steel
Mild steel
Brass
Copper
Aluminium
Scale
C (Black
graduations)
B (Red
graduations)
Type of
Indentor
Diamond cone
Ball (1/16’’)
Ball (1/16’’)
Ball (1/16’’)
Ball (1/16’’)
(VII) Precautions:
 The specimen should be cleaned properly.
1
RHN
2
Total load(P)
Kg-F
150
100
3
Average
RHN
 Readings must be taken carefully and correctly.
(VIII) Result:
Rockwell hardness Number of the given specimen is
 Hardened steel =
 Mild steel =
 Brass =
 Copper =
 Aluminium =
(IX) Conclusion:
(X) References:
1. Metals Handbook, 9th ed., Mechanical Testing, Vol. 8, 1990.
2. G. Dieter, Mechanical Metallurgy, S1 ed., Mc Graw Hill, 1986.
3. N. Dowling, Mechanical Behavior of Materials, Prentice Hall, 1993.
B) BRINELL HARDNESS TEST
(I) Aim: To determine the Brinell hardness number of the given Specimen
using Brinell hardness tester.
(II) Apparatus:



Brinell hardness testing machine and Brinell Microscope.
Ball Indentor of diameter 2.5mm and 5mm
Specimens (Mild steel, Brass, Copper, Aluminum)
(III) Theory: The Brinell Hardness Test is used to determine the Hardness Number of
hard, moderately hard, and soft material E.g.: Brass, Bronze, Aluminum, Gold, and
Copper. Very hard material and Brittle material cannot be tested by Brinell hardness
tester. Brinell hardness number (BHN) is obtained by the ratio of the calculated load and
the spherical area of the Indentation or Impression made on the specimen by the
corresponding Indentor Ball. In Brinell hardness test, a steel ball of diameter (D) is forced
under a load (F) on to a surface of the test specimen. Mean diameter (d) of indentation is
measured after the removal of the load (P). The Brinell Hardness Number (BHN) is
obtained by dividing the applied force P, in kg-F; by the curved surface area of the
indentation, which is actually a segment of a sphere.
Since the deformations caused by an indenter are of similar magnitude to those occurring
at the ultimate tensile strength in a tension test, some empirical relationships have been
established between hardness and engineering ultimate tensile strength of metals and
alloys. For example, for steels UTS can be roughly estimated from Brinell hardness as
follows:
UTS (in MPa) = 3.45 x BHN
Suitable Application:



Brinell hardness test is used for materials with a coarse or inhomogeneous
grain structure.
It is used for larger samples.
It is also suitable for forgings and castings where the structural elements are
large.
(IV) Equipment Description:
Figure 2: Brinell hardness testing machine.
(V) Procedure:
a) Keep the loading and unloading lever at position “A” which is unloading position.
b) Select suitable indentor & weights according to the scale.
c) Place the specimen on testing table anvil.
d) Turn the hand wheel to raise a job until it makes contact with indenter & continue
turning till the longer pointer at the dial gauge makes 2 ½ rotations. Then it stops at zero
continue turning slowly till the small pointer reaches the red spot at 3‟, this is automatic
zero setting dial gauge.
e) Turn the lever position “A” to “B” i.e. from unloading to the loading position. So that
the total load will act.
f) When the longer pointer of the dial gauge reaches steady position, take back the lever
to the unloading position “A”. [Avoid sudden release at the lever]
g) Remove the job from the platform and note down the diameter of the indentation
using Brinell microscope.
h) Using the appropriate formula calculate BHN.
i) Similarly, repeat the step from ‘a-h’ for different trials and for different metals.
(VI) Observation and Calculation:
Type of
Indentor
Ball Indentor
2.5mm diameter
Ball Indentor
5mm diameter
S/
No
Specimen
01
02
03
04
Mild steel
Brass
Copper
Aluminium
Total load(P)
Kg-F
187.5
Total
load(P)
Kg-F
250
Suitable for
Nonferrous soft metals, Soft iron, steel
castings, Cast iron, malleable iron.
Light alloys casting, forging alloys, die
casting alloys.
Indentor
Diameter(D)
in mm
Diameter of
Indentation(d)
in mm
1
2
3
Average
Diameter
(mm)
BHN
Brinell hardness number (BHN) =

Where,
The Brinell hardness number is expressed as (value in N/mm2)
D = Diameter of ball indentor in mm
d= Diameter of Indentation in mm
P= Load applied in Kgf
Least Count of Brinell Microscope=0.01mm
(VII) Precautions:
 The specimen should be well cleaned.
 Place the specimen properly.
 Reading must be taken carefully and correctly.
 Remove the load after applying.
(VIII) Results:
Brinell hardness number of the given specimen is
 Mild steel =
 Brass =
 Copper =
 Aluminium =
(IX) Conclusion: Based on BHN for Mild Steel, the Relation between the tensile strength
and Hardness Number is given as follows,
Tensile Strength of Mild Steel = … K*BHN for MS
Where K= constant (for types of steel from 3.4 to 3.9).
(X) References:
1. Metals Handbook, 9th ed., Mechanical Testing, Vol. 8, 1990.
2. G. Dieter, Mechanical Metallurgy, S1 ed., Mc Graw Hill, 1986.
3. N. Dowling, Mechanical Behavior of Materials, Prentice Hall, 1993.
C) VICKERS HARDNESS TEST
(I) Aim: To determine the hardness of the given Specimen using Vickers hardness test.
(II) Apparatus:

Vickers Hardness Testing Machine.

Diamond cone indentor,

Specimen.
(III) Theory:
Very Hard materials (e.g. Mild steel, case hardened steel, etc,) can be tested by the
Vickers’ method. If the moderately hard materials like Brass, Copper and Aluminum are
tested in this machine, the indentor makes a deep impression. Hence, a proper
indentation cannot be made on the specimen and correct value of the hardness cannot
be obtained for these materials by V. H. Test.
VHN = Load Sloping or pyramidal area of the indentation
This test is similar to the Brinell hardness test similar relationship and eliminates most of
the errors. The produced impression is projected onto a focusing screen and the
diagonals of the impression are measured by means of the measuring equipment. Due
to small impressions, it is very suitable for testing polished and hardened material
surfaces. This test is rapid and accurate. The required load as calculated by P/D2 ratio is
applied on the specimen for a standard time of 8-10 seconds and BHN is calculated by
the ratio of load and the spherical area of indentation. The diameter of the indentation is
measured on the focusing screen of the machine.
Suitable Application:

Vickers hardness test is used for hardness testing of all solid materials,
including metallic materials.

It is suitable for a wide range of applications.

It can also be used for a sub-group of hardness testing of welds.
(IV) Equipment Description:
Figure 3: Vickers Hardness Testing Machine.
(V) Procedure:
a) Clean the surface at the specimen
b) Fix the indentor in the hardness tester and switch on the power supply.
c) Place the specimen with a cleaned surface facing the indentor on the anvil at work
table.
d) Focus the workpiece surface for clean visibility by rotating the hand wheel at the work
table upwards and downwards.
e) Select the load specified (P) push button available on the right side at the hardness
tester.
f) Actuate the electric push button (Green Button) at the front for loading, the loading lever
starts moving up words and reaches the study position.
g) Now release the loading lever slowly and bring it to the downward position.
h) For major reading adjust the display at the indentation made by the indentor to coincide
with the micrometre on the display screen.
i) For major (minor) reading adjust the movable side at the micrometre and note down the
total reading.
j) The measurement is to be made for two opposite corners of the diagonal indentation
denoted as (l).
k) Repeat the above procedure for different material.
(VI) Observation and Calculation:
Type of indentor = Diamond cone
S/No
Specimen
Load
applied
in Kg-F
Length of Indentation
in mm(l)
1
2
3
Average
length
in mm
Vickers Hardness Number (VHN) =
Where,
P= Load applied in Kg
l= Average length of the diagonal L in mm
Least count of microscope=0.001mm
1st scale each division =0.1mm
2nd scale each division =0.01
3rd scale each division =0.001mm
(VII) Precautions:
 The specimen should be well cleaned.
 Place the specimen properly.
 Reading must be taken carefully and correctly.
(VIII) Results: Vickers hardness Number of the given specimen is
 Mild steel =
 Hardened mild steel =
(IX) Conclusion:
(X) References:
1. Metals Handbook, 9th ed., Mechanical Testing, Vol. 8, 1990.
2. G. Dieter, Mechanical Metallurgy, S1 ed., Mc Graw Hill, 1986.
3. N. Dowling, Mechanical Behavior of Materials, Prentice Hall, 1993.
Compiler: Ifeyinwa Ijeoma Obianyo
PhD Candidate,
Department of Materials Science and Engineering,
African University of Science and Technology, Abuja.
Date: 03/03/2019
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