Physical Property Identification Through
Modulus and Indentation Testing
Experiment 2
Alex High
MatSE 462, Section 4
28 March 2015
Abstract
Physical properties are crucial in the selection of materials. Tests that
determine and standardize these properties are equally vital. For any material, a
value such as the elastic modulus needs to be known. This experiment aimed to
identify some of the important physical properties as well as aimed to test the
reliability of the testing methods. Overall, the property tests were successful and
produced excellent results.
Introduction
Four experiments were conducted on selected materials, with the intent of
identifying various physical properties about these metals. Rockwell Hardness, Vicker’s
Indentation, Charpy Impact, and sound velocity testing were the conducted experiments.
Through these experiments, values such as hardness, toughness, elastic modulus and
Poisson’s ratio were determined. The Rockwell Hardness tests were conducted on metals
and on metal alloys, specifically 1340 steel, 1144 steel, 6061 aluminum and 260 brass.
The Vicker’s Indentation tests, for hardness and toughness, were conducted on the
ceramic Yb:YAG. The sound velocity tests were conducted on zirconia (ZrO2),
aluminum, Teflon, and silicon carbide (SiC). The Charpy Impact tests were conducted on
0.2 wt%-carbon steel.
Experimental Procedures
The four tests were conducted in specific manners. The Rockwell Hardness test
was conducted using the following procedure on a LECO RT-240 hardness tester. For
1340 steel, 6061 Al and 260 brass, as well as for most tests with 1144 Steel, the HRB
scale was used. The HRB scale utilized a load of 100 kgf along with a tungsten carbide
(WC) indenter tip. The HRB scale was implemented because of the softer nature of these
metals. However, for two tests conducted on 1144 steel, the HRC scale was used, due to
1144 steel being a harder alloy. HRC utilized a load of 150 kgf with a diamond indenter
tip. Once the appropriate scale was selected, the sample, with flat and parallel faces, was
placed onto the stage. Care was taken to ensure that the indenter tip was at minimum two
indent diameters from existing indents. The stage was turned upwards until the tip came
into contact with the sample, at which point the stage clicked into place and the machine
ran its test.
The Vicker’s Indentation tests were conducted using two machines. A LECO
MHT Series 200 was used to determine the toughness of samples while a LECO V-100C1 was used to determine the hardness of samples. The samples were polished goldcoated Yb:YAG. For the toughness measurements on the MHT Series 200, a load of 0.5
kgf was used. For the hardness measurements on the V-100-C1, a 0.3 kgf load was used.
Both machines operated very similarly, and both used the ConfiDent software.
The actual sample testing was conducted using the following procedure. The
sample was placed onto the stage, and the stage was moved, if necessary, to ensure that
the future indent, shown on the screen, would be more than three indent diagonals away
from existing indents. The mode was then rotated from the microscope to the indenter tip,
and the test was started. Once the test had concluded, the mode was rotated back to the
microscope objective, which was subsequently refocused, and the “capture” program was
selected. For the hardness tests, the four lines were moved to the corners of the indent.
For the toughness tests, the four lines were moved to the end of the cracks that had
propagated from the corners of the indent. Take care to ensure that the indent is similar to
the images in Figure 1. Any other indent figure, with either large cracks or asymmetrical
sides, etc. are unacceptable, and the sample must thusly be indented again.
Figure 1. – Accepable indent figures.
The sound velocity test was conducted to identify the elastic modulus and the
Poisson’s ratio of several materials. The samples tested were ZrO2, Al, Teflon and SiC.
The tests were conducted using the following procedure. First, the appropriate
transducers were selected and screwed on, depending on whether the test was in
longitudinal mode or in shear mode. A small drop of coupling fluid was applied to one of
the transducer faces, and the faces were rubbed together to spread the fluid over both
faces. For the longitudinal mode, Couplant A was applied, and for the shear mode, honey
was applied. For any shear mode test, the transducer heads were aligned according to the
arrows on the heads. The time scale on the oscilloscope was zeroed by squeezing the
transducer heads together. The left vertical cursor line was aligned with the trough/peak
of the first valley/peak. The test was then conducted with the sample between transducer
heads. The trough/peak shift was marked using the right vertical cursor, and the time
difference between left and right cursor was recorded.
The Charpy tests were conducted on 0.2 wt%-C steel. The tests were conducted
using the following procedure. A notched bar sample, at a known temperature, was
placed on the stage, and the pendulum hammer was raised to lock. The test was then
conducted, and the values were recorded. The following two types of samples were used
in these tests: longitudinal, where the sample lengths were cut parallel to the rolling
direction; and transverse, where the sample lengths were cut perpendicular to the rolling
direction.
Results and Discussion
The time difference for the sound velocity was used to calculate the elastic
µ
modulus and the Poisson’s ratio of the tested materials. Using the equation, 𝑐𝑠 = √𝜌,
where cs is the wave speed and ρ is the density, the bulk modulus, µ, can be calculated
which in turn allows for the calculation of the Poisson’s ratio, the shear modulus and the
elastic modulus for each tested material2. The average calculated elastic modulus and
Poisson’s ratio are listed in Table 1.
ZrO2
Avg.
STD
93.93 4.77
SiC
Avg.
STD
311.11 36.06
Al
Avg.
STD
70.25
2.37
Teflon
Avg.
STD
1.416
0.098
Elastic
Modulus
(GPa)
Poisson’s 0.181 0.059
0.106
0.079
0.328
0.023
0.43
0.023
ratio
Table 1. – Average elastic modulus and Poisson’s ratio values for materials tested using
sound velocity.
Standard values give that ZrO2 has an elastic modulus of 126 GPa, which falls outside of
three standard deviations of the calculated elastic modulus. Additionally, the standard
Poisson’s ratio is given as 0.185, which within three standard deviations of the calculated
0.181 ratio. The SiC has a standard elastic modulus of 416 GPa, which falls within three
standard deviations of the calculated 311.11 GPa value. SiC’s standard Poisson’s ratio of
0.14 is exactly three standard deviations away from the calculated value. For aluminum,
the standard value of 70 GPa matches the calculated value exactly, while the Poisson’s
ratio is very similar as well. The elastic modulus of Teflon, approximately 9.0 GPa
(23°C) is not within three standard deviation values of the calculated value1. However, its
Poisson’s ratio of 0.46 (at 23°C) is well within three standard deviations of the calculated
value1.
There is an obvious source of error in these calculations, and that arises from the
subjectivity of the test. The velocity reading relies heavily on how tightly the transducers
were held on either side of the sample. This variability has great potential in skewing
results.
The Rockwell Hardness value standards were all within three standard deviations
of the calculated values (Table 2). This test was extremely mechanized and had little
room for human error3.
1340 Steel
1144 Steel
6061 Al
260 Brass
Avg.
STD
Avg.
STD
Avg.
STD
Avg.
STD
HRB
99.9
0.94
77.5
1.81
58.3
5.78
HRC
53.7
2.05
22.7
0.21
Table 2. – Average Rockwell Hardness values for selected metals and metal alloys.
The Vicker’s tests (Table 4, 5) were similar in mechanization to the Rockwell tests, and
again, the calculated values all were similar to the standard values3.
Yb:YAG
Yb:YAG Class
Avg.
STD
Avg.
STD
HV
513
15.21
512.5385 19.57
Table 3. – Average Vicker’s Indentation Hardness values for Yb:YAG.
Yb:YAG
Avg.
STD
Yb:YAG Class 1
Avg.
STD
Yb:YAG Class 2
Avg.
STD
KIC
115
14.52
87.70
11.08
87.57
10.41
Table 4. – Average Vicker’s Indentation Toughness values for Yb:YAG.
The Charpy Impact test provided data, which was plotted in Chart 1. Since each
sample was tested at a specific temperature, this data could be plotted versus energy
absorbed (in ft-lbs) to assist in the identification of the ductile-to-brittle transition
temperature. These values will be different for the transverse and the longitudinal
samples due to the possible failure directions based on slip mechanisms. These
temperatures are demarcated by the vertical black lines in the graph. For the longitudinal
sample, the ductile-to-brittle transition temperature is -50°C. For the transverse sample,
the ductile-to-brittle transition temperature is -37°C.
Chapy Impact Toughness
Transverse
90
80
Longitudinal
70
CVN (f-lbs)
60
50
40
30
20
10
Temperature (°C) 0
-80
-60
-40
-20
0
20
40
Chart 1. – Charpy Impact Toughness with ductile-to-brittle transition temperature.
Conclusion
Ultimately, the property tests were extremely successful. The tests were consistent
in providing the appropriate values. The only real error, or possible source of error, in
testing occurred in the sound velocity tests, where results were affected by how tightly
the transducer heads were applied to the sample. This resulted in skewed results for
materials such as ZrO2. However, the hardness and toughness tests provided excellent
data, making the overall experiment successful.
Citations
1. Teflon PTFE, DuPont. 3/27/15.
< http://www.rjchase.com/ptfe_handbook.pdf>
2. Standard Practice for Measuring Ultrasonic Velocity in Materials, ASTM
International. https://cms.psu.edu/Merge/2009/MRG-150103-132958ERB105/_assoc/1D6B8A3A76B544A183E5410A414DB396/ASTM_Standar
d_E494-10_Ultrasonic_Velocit.pdf
3. Standard Hardness Conversion Tables, ASTM International.
<https://cms.psu.edu/Merge/2009/MRG-150103-132958ERB105/_assoc/A73AE97AF1354C9ABEA2F0C5247D17CC/ASTM_Standa
rd_E140-12b_Std_Hardness_Conv.pdf>