CE 3410
Mechanics of Materials Lab
Louisiana State University
Laboratory Report No. 1
Hardness Test
by
Joshua Board
Table of Contents
Purpose:............................................................................................................................... 3
Introduction: ........................................................................................................................ 3
Apparatus and Test Procedures:.......................................................................................... 7
Results:.............................................................................................................................. 11
Discussion: ........................................................................................................................ 13
Sample Calculations: ........................................................................................................ 17
Brinell Hardness Test .................................................................................................... 17
Rockwell Hardness Test ............................................................................................... 18
Conclusion: ....................................................................................................................... 19
References ......................................................................................................................... 20
Appendix ........................................................................................................................... 21
Appendices A1 – Original Test Data Sheet .................................................................. 21
Appendix A2 – Material Properties of Steel ................................................................. 22
Appendix A3 – Material Properties of Aluminum ....................................................... 23
TABLE OF FIGURES
FIGURE 1 - BRINELL HARDNESS TESTER MODEL HB3000B ......................................................................................... 7
FIGURE 2 - ROCKWELL HARDNESS TESTER MODEL C504 ............................................................................................ 7
FIGURE 3 - RELATIONSHIP BETWEEN BRINELL EXPERIMENTAL HARDNESS AND REFERENCE HARDNESS ................................ 13
FIGURE 4 - RELATIONSHIP BETWEEN ROCKWELL EXPERIMENTAL HARDNESS AND REFERENCE HARDNESS ............................ 14
FIGURE 5 - COMPARISON OF TENSILE STRENGTH BASED ON BRINELL, ROCKWELL, AND REFERENCE DATA ............................ 15
TABLE 1- BRINELL STANDARDS FOR LOAD, TIME, AND HARDNESS ................................................................................. 4
TABLE 2 - RELATIONSHIP BETWEEN HARDNESS NUMBERS AND TENSILE STRENGTH........................................................... 6
TABLE 3 - BRINELL HARDNESS TEST DATA AND RESULTS ............................................................................................ 11
TABLE 4 - ROCKWELL HARDNESS TEST DATA AND RESULTS ......................................................................................... 12
Purpose:
The purpose of this laboratory is to determine the hardness and the tensile
strength of three metal samples: 1020 Steel, 6061 Aluminum and 2024 Aluminum. The
Brinell and Rockwell Hardness Tests are used to determine this. With the results obtained
from each sample, the engineer will be able to determine how the samples relate to each
other. Both the Brinell and Rockwell Hardness Test are considered to be non-destructive.
Introduction:
Hardness is the resistance of a material to penetration or abrasion under a locally
applied load (Ref. 1). We use the concept of hardness almost every day. Any time we file
our nails with a nail file or scratch a CD with our finger nails, hardness is involved.
Hardness is used to measure a variety of resistances including: scratching, cutting, and
indenting (Ref. 2). Also, Hardness may be used for grading similar materials, checking or
controlling quality level and controlling uniformity of tensile strength (Ref. 2).
As engineers, we find hardness tests useful for estimating the tensile strength of
materials. The Brinell and Rockwell Tests are the most common experiments to
determine the hardness of metals. Both Tests measure the resistance to indentation of a
metal under a static load. However, as the technology has increased the usage of very
hard steels, very thin materials, very small sized parts, etc, a number of other hardness
tests have developed, and not just for metals but for wood, rubber, plastic, and paving
materials (Ref. 2).
The Brinell Test procedures and specifications can be found in ASTM E10. The
test consists of applying a load through a steel ball with a 10-millimeter diameter for a
specific period of time. The standard for load amount, time period and hardness is shown
below in Table I.
Table 1- Brinell Standards for Load, Time, and Hardness
If the sample is expected to have a Brinell Hardness Number (BHN) greater than 450, an
indenter made of a harder material should be used (Ref. 2). After removing the load, an
indentation is left on the metal sample. By measuring the diameter of the indentation and
using the known diameter of the steel ball that applies the load, the spherical area is
calculated. The Brinell Hardness Number (BHN) is the ratio of the applied load in
kilograms to the spherical area of the indentation in mm2 (Ref. 1). In order to find the
BHN, the following equation is used:
Equation (1)
Where:
D = diameter of the steel ball, mm
d = diameter of the indentation
P = load, kg
The Brinell Hardness Number is used to give an estimation of the tensile strength of the
metal using the following equation:
T.S. = 500 x BHN
Equation (2)
Where:
T.S. = tensile strength, psi
BHN = Brinell Hardness Number
The Rockwell Test procedures and specifications can be found in ASTM E18.
This test uses the depth of indentation to determine the hardness number (Ref. 1). A
minor load is applied to hold the sample in place then a major load is applied to indent
the sample. The Rockwell Test is similar to the Brinell Test because both use indentation
of a samples surface to determine hardness; however, the Rockwell Test measures depth
of indentation not diameter as in the Brinell Test. The Rockwell Test uses smaller loads
and creates smaller indentations on the sample as well (Ref.2). Also the Rockwell
Hardness Tester has a gauge on the machine that will display the Rockwell Hardness
Number, RHN, after the load is removed.
For this test, a variety of indenters are used including: steel balls ranging from
1
/16-inch to ½-inch and spheroconical diamond tips (Ref.1). There are three standard
loads of 60, 100, and 150 kilograms that can be applied to a sample. Diamond tips along
with a load of 150 kg are used for hard steel, while steel balls and a load of 100 kg is used
for softer steel and aluminum. The gauge on the machine has two sets of numbers, a red
and a black. 30 hardness numbers offset the scales with the black scale being the lower of
the two (Ref.2). Each scale also provides a different pre-fix to be recorded with the
hardness number, B for red and C for black. The combination of indenter and applied
load leads to what set of numbers, red or black, are used to measure the Rockwell
Hardness Number. A diamond tip with applied load of 150 kg corresponds to the black
scale and a steel ball with 100 kg corresponds to the red scale.
The Rockwell Test is used for materials that are beyond the capabilities of the
Brinell Test and because the Rockwell Hardness Number is shown on the machine if
returns faster and more accurate hardness numbers (Ref. 2). However, the Rockwell test
does not have such an easy way to calculated tensile strength as was afforded to us by the
Brinell Test. In order to determine tensile strength, a standardized table showing the
relationship between Rockwell Hardness Numbers, tensile strength and other properties
has been developed and is provided below in Table II.
Table 2 - Relationship between Hardness Numbers and Tensile Strength
Picture taken by Joshua Board
Apparatus and Test Procedures:
Picture taken by Joshua Board
Figure 1 - Brinell Hardness Tester Model HB3000B
Figure 2 - Rockwell Hardness Tester Model C504
The Apparatus used for the Brinell Hardness Test is Model HB-3000B, shown in
Figure 1. The apparatus used for the Rockwell Hardness Test is Model C504, shown in
Figure 2.
The Brinell Hardness Test requires the use of the following:
1- Brinell Hardness Tester Model HB-3000B (shown in Figure 1)
1- Testing Block with known BHN
3- Metal test samples
1- Microscope of low power
1- Ten millimeter diameter steel ball
The Rockwell Hardness Test required the use of the following:
1- Rockwell Hardness Tester Model C504 (shown in Figure 2)
1- Testing Block with known RHN
3- Metal test samples
1- 1/16 inch diameter steel ball
Both the Brinell and Rockwell Hardness Tests require three metal cubes with 1-inch sides
to be the test samples. The samples to be tested are 1020 Steel, 6061 Aluminum and 2024
Aluminum. Before the test, each sample is inspected for any defects to the surface that
could affect the results. All three samples were clean and passed inspection.
The Brinell Test consists of pressing a steel ball of 10-millimeter diameter into
the test sample for a standard amount of time, which will be 12 seconds for our
laboratory. The 10-mm steel ball will impose a load of 3000 kg for steel samples and
1500 kg for aluminum samples. This load will cause a depression to remain on the
surface of the sample after the load is removed. The spherical area of the indentation can
be calculated from the diameter of the indenter and the diameter of the depression on the
surface of the sample. For the Brinell Test, the steel ball must not deviate in diameter
more than 0.01 mm and balls of harder material are to be used if the sample has a known
BHN greater than 450 (Ref. 1). Before starting either test, a test block was used on both
the Brinell and Rockwell testers in order to verify accurate results. Tests should not be
made too close together or too close to the edge of the sample.
Procedure for Brinell Hardness Test:
1. Verify using the test block that the machine is accurate.
2. Determine the proper load to apply to the sample: 3000 kg for steel
and 1500 kg for aluminum.
3. Set the amount of time for the test. In this lab we will use 12 seconds
as our test time.
4. Select a test area on the sample, being sure to stay away for the edges
and other indentions made on the sample.
5. Turn the screw until the sample and the steel ball contact each other
and continue to turn the screw until the screw slips.
6. Push “Start” to begin the test and create an indentation on the sample.
7. Repeat step (4)-(6) two times so that a total of 3 indentations are on the
sample.
8. Measure the diameter of each indentation with a low power
microscope.
9. Determine the Brinell Hardness Number using Equation (1).
The Rockwell Hardness Test uses a steel ball 1/16-inch in diameter to indent the
surface of a sample. This test uses a smaller load and indenter therefore the indentation is
smaller and shallower. Similar to the Brinell test, the hardness number found by the
Rockwell Test is a function of the indentation on the surface of the sample caused by the
indenter under a static load (Ref. 2). However, the Rockwell Test is faster because the
Rockwell Hardness Number is read straight from the machine. The Rockwell Hardness
Number, RHN, is inversely related to the depth of indentation.
Procedure for Rockwell Hardness Test:
1. Verify using the test block that the machine is accurate.
2. Determine the indenter to use. In this lab we will use a steel ball 1/16inch in diameter.
3. Select a test area on the sample, being sure to stay away for the edges
and other indentions made on the sample.
4. Raise the sample against the indenter by turning the large screw until
the center gauge is vertical.
5. Use the small screw to set the dial reading to zero.
6. Press the lever down to start the test.
7. Read the RHN from the red scale on the dial and include the prefix
“B”.
8. Repeat steps (3)-(7) four times so that a total of five indentations are
on the sample.
Results:
The Table III below shows the data from the Brinell Hardness Test. Three
diameter readings were recorded for each sample. The mean of the results for each
individual sample is calculated and used as the diameter of the indentation. Knowing the
applied load, the diameter of the indenter and the diameter of the indentation, equation
(1) is used to find the Brinell Hardness Number for each sample. Using Equation (2), the
tensile strength is determined.
Table 3 - Brinell Hardness Test data and results
Brinell Hardness Test Data and Results
Type of Material
1020 Steel
2024 Aluminum 6061 Aluminum
Test No.
Diameter (mm)
1
4.30
3.90
4.30
2
4.40
3.80
4.30
3
4.40
3.80
4.25
Mean
4.37
3.83
4.28
BHN
190
125
99.2
Tensile Strength (psi)
95000
62500
49600
Reference BHN*
179
120
95
Reference Tensile
Strength (psi)*
87000
70000
45000
Table IV below shows the results of the Rockwell Hardness Test. Five tests were
completed on each sample and the mean of each sample is calculated. The mean is
recorded and used as the Rockwell Hardness Number, RHN, for each sample. Using
Table II, the tensile strength of each sample is interpolated.
Table 4 - Rockwell Hardness Test data and results
Rockwell Hardness Test Data and Results
Type of Material
1020 Steel
2024 Aluminum 6061 Aluminum
Test No.
Diameter (mm)
1
91.7
77.7
58.9
2
93.0
78.2
58.6
3
93.0
79.0
58.1
4
93.2
78.9
59.1
5
93.0
78.0
59.0
Mean
92.8
78.4
58.7
Tensile Strength (psi)
96071
71750
51360
Reference RHN**
88
75
60
Reference Tensile
Strength (psi)**
87000
70000
45000
Discussion:
Figure 3 below shows a graph of the relationship between the experimental BHN
and the reference BHN obtained from MatWeb (Ref. 3), for both the steel and aluminum
samples. The results show only a small deviation from the reference data and it should be
noted that 1020 steel showed the most deviation at 5%. Also, each sample out preformed
the reference hardness number recording higher values for hardness.
200
180
160
Brinell Hardness Number
140
120
100
BHN
Ref. BHN
80
60
40
20
0
1020 Steel
2024 Aluminum
6061 Aluminum
Figure 3 - Relationship between Brinell Experimental Hardness and Reference Hardness
Figure 4, shown below, contains a graph of the experimental RHN and the
reference hardness numbers given on MatWeb (Ref. 3). Both steel and aluminum samples
remained close to the reference hardness with steel once again being 5% off of reference,
but it is interesting to point out that 6061 Aluminum has fallen below the reference data
provided by MatWeb (Ref. 3). In all other cases the hardness of the samples has exceeded
that of the reference hardness. After comparing the data, both the Brinell and Rockwell
test are producing accurate numbers and a maximum deviation of 5% over all further
backs up both tests accuracy.
100.0
90.0
80.0
Rockwell Hardness Number
70.0
60.0
50.0
RHN
Ref. RHN
40.0
30.0
20.0
10.0
0.0
1020 Steel
2024 Aluminum
6061 Aluminum
Figure 4 - Relationship between Rockwell Experimental Hardness and Reference Hardness
120000
100000
Tensile Strength (psi)
80000
60000
Brinell Tensile Strength (psi)
Rockwell Tensile Strength (psi)
40000
20000
0
1020 Steel
2024 Aluminum
6061 Aluminum
Figure 5 - Comparison of Tensile Strength based on Brinell, Rockwell, and Reference data
Figure 5 above shows a comparison of the tensile strength recorded for each
sample based on the Brinell and Rockwell tests. The graphs show that the Rockwell test
recorded higher tensile strength for each of the samples but both 1020 steel and 6061
aluminum were determined to have values that were similar. The sample of 2024
Aluminum recorded interesting results as the greatest difference between the Brinell
strength and Rockwell strength was found here. The Brinell test is more accurate for
finding tensile strength, based on Equation (2)’s simplicity, where the Rockwell test has
more room for error when interpolating Table II. For both tests, steel was determined to
be the sample that exceeded the reference values for tensile strength by the most. 6061
Aluminum was found by both tests to be harder than the reference values. For 2024
Aluminum, the Rockwell test showed expected results, however the Brinell test
determined that the 2024 Aluminum was not as strong as the reference tensile strength.
Looking through the formulas, it seems that the Brinell Hardness Tests was able to create
too large of an indentation in the surface of the 2024 Aluminum, recording a diameter of
3.83 mm. An indentation closer to 3.63 mm would have given the correct tensile strength
according to the reference data.
From the results shown it Figures 4, 5 and 6, it is clear that some errors have
occurred. The Brinell Test required the reading of the diameter through a scope which
could have lead to inaccuracies due to human error. Also it is possible that the load was
prematurely removed from the sample before the 12 seconds had expired. For the
Rockwell test it is possible that the numbers on the gauge were incorrectly read.
However, there are other sources of error that can be pointed to in this lab. During the set
up of the experiment it was noticed that the last inspection of the equipment was in 1999
and the label stated that both machines need to be inspected yearly.
Sample Calculations:
Brinell Hardness Test
(1020 Steel) Brinell Hardness Number, BHN
D = 10-mm
P = 3000 kg
d = 4.37-mm
BHN = 190
Tensile Strength = BHN x 500
= 190 x 500
= 95000 psi
Rockwell Hardness Test
(1020 Steel) Rockwell Hardness Number, RHN
RHN = 92.8
(Read for gauge on Rockwell Tester)
Tensile Strength = 96071
(Found using Table II)
Conclusion:
The Brinell and Rockwell experiments are two tests that are both designed to test
the hardness of a metal sample. The Brinell test measures the diameter of an indentation
in order to obtain a hardness number and the Rockwell test measures the depth of
penetration and returns a hardness number. Both tests are similar in this way but each
offered its own individual advantages: Brinell with its ease of calculating tensile strength
and Rockwell with its direct readings of hardness number for the machine. Both
experiments are also considered non-destructive.
Looking at the results it seems that both tests found our samples for the most part
to be harder than the reference numbers indicated. The most likely source of error
however seems to be the decade between inspections for both machines leading to
uncertainty in the numbers they are providing. In future tests, more experience with the
machine and metal samples along with better maintenance of the equipment would help
to reduce errors. The recorded error for the hardness numbers was less than 5% for both
the Brinell and Rockwell Hardness Tests and therefore each test can be considered
reasonably accurate in terms of the tensile strength of a sample.
References
1. Mechanics of Materials Laboratory Manual CE 3410, Department of Civil and
Environmental Engineering, Spring 2007, pT1-1 – T1-10.
2. Jacobs, C., CE 3410 Notes – “Hardness Testing”, received in class on January 13, 2009.
3. www.MatWeb.com
4. ASTM E 10 Standard Test Method for Brinell Hardness of Metallic Materials, ASTM
International, April 2001.
5. ASTM E 18 Standard Test Method for Rockwell Hardness and Rockwell Superficial
Hardness of Metallic Materials, ASTM International, April 2001.
Appendix
Appendices A1 – Original Test Data Sheet
Brinell Hardness Test Rockwell Hardness Test
(Diameter, mm)
(RHN)
1020 Steel
4.37
91.7
93.0
93.0
93.2
93.0
6061 Aluminum
4.28
58.9
58.6
58.1
59.1
59.0
2024 Aluminum
3.88
77.7
78.2
79.0
78.9
78.0
Appendix A2 – Material Properties of Steel
Mechanical Properties
Metric
English
Hardness, Brinell
179
179
Hardness, Knoop
200
200 Converted from Brinell hardness.
88
88 Converted from Brinell hardness.
Hardness, Rockwell B
Hardness, Vickers
Tensile Strength, Ultimate
188
188 Converted from Brinell hardness.
600 MPa
370 MPa
87000 psi
53700 psi
Elongation at Break
23.00%
23.00%
Reduction of Area
64.20%
64.20%
200 GPa
140 GPa
29000 ksi
20300 ksi
0.29
0.29
Tensile Strength, Yield
Modulus of Elasticity
Bulk Modulus
Poissons Ratio
Comments
in 50 mm
Typical for steel
Typical for steel
Appendix A3 – Material Properties of Aluminum
Mechanical Properties
Hardness, Brinell
Hardness, Knoop
Metric
English
Comments
120
120
AA; Typical; 500 g load; 10 mm ball
150
150
Converted from Brinell Hardness Value
Hardness, Rockwell A
46.8
46.8
Converted from Brinell Hardness Value
Hardness, Rockwell B
75
75
Converted from Brinell Hardness Value
137
137
Converted from Brinell Hardness Value
483 MPa
345 MPa
70.0 ksi
50.0 ksi
AA; Typical
18.00%
18.00%
AA; Typical; 1/16 in. (1.6 mm) Thickness
Hardness, Vickers
Ultimate Tensile Strength
Tensile Yield Strength
Elongation at Break
AA; Typical
Modulus
AA;ofTypical;
Elasticity
Average of tension
and compression.
73.1 GPa
10600 ksi Compression modulus is about 2% greater than tensile modulus.
Notched Tensile Strength
Ultimate Bearing Strength
Bearing Yield Strength
Poissons Ratio
Fatigue Strength
379 MPa
855 MPa
524 MPa
55000 psi
124000 psi
76000 psi
0.33
0.33
138 MPa
20000 psi
2.5 cm width x 0.16 cm thick side-notched specimen, K t = 17.
Edge distance/pin diameter = 2.0
Edge distance/pin diameter = 2.0
completely reversed stress; RR Moore machine/specimen
@# of Cycles 5.00e+8
@# of Cycles 5.00e+8
Machinability
Shear Modulus
Shear Strength
70.00%
70.00%
0-100 Scale of Aluminum Alloys
28.0 GPa
283 MPa
4060 ksi
41000 psi
AA; Typical