1. Rna Waheb Rameen Hassanzadeh
Ryan Oh Pavan Kumar Nanne
Dhaval Prajapati Siddhesh Sawant
Lab Time: Wednesday 8 pm
Lab Group #2
MSE 527 Lab # 1 – Impact Test Lab
Abstract
The Charpy Impact Test was used to measure the impact energy of 1018 Carbon Steel and 6061
Aluminum at varying temperatures. Between 50ºF to -25 ºF, the impact of energy of aluminum was found to
sharply decrease from 33 ft-lbs to 15 ft-lbs whereas the impact energy of steelwas relatively unaffected by
temperature. The amount of impact energy aluminum can absorb was evidenced through the % shear lip, which
was observed from the fracture surfaces. The fracture toughness of both materials was also found to be
unaffected by temperature. Graphs showing the effect of temperature on impact energy, fracture toughness, %
shear lip, and changes in width were obtained.
Procedure
The purpose of the Charpy Impact Test was to characterize the toughness of materials as a function of
temperature under impact loading and multi-axial stress state1
. A pendulum impact testing machine with a heavy
weight was used to perform the tests. It was accurately adjusted by performing a test without a sample and with
the drag indicator to the left. The drag indicator stopped at position zero proving that the machine is correctly
calibrated.
The experiment was performed on 5 samples of 6061 Aluminum and 5 samples of Carbon steel at 5
different temperatures. Samples were marked for orientation and their widths were measured. Afterwards,5 sets
of aluminum and steelwere placed in their respective dry ice/acetone,antifreeze/water mix with dry ice, ice/pure
water,room temperature, or boiling water bath for 10 minutes to ensure thermal equilibrium. The samples were
then quickly transferred to the Charpy Impact Test,fractured, and had their impact energy measured. Their
fracture surfaces were then examined measured and compared to standards to determine % shear lip.
Results and Discussion
Table 1 shows the impact energy absorbed by the samples at their respective temperatures. The impact
energy of Aluminum 2, the sample that was submerged in ice water,was not found due to a mechanical error.
After the sample was placed, the pendulum was set and released,however the drag indicator did not move.
Table 1 also shows their % shear lip, an indication of a sample's brittleness, which was determined by examining
their fracture surfaces and comparing them with standards. Table 2 shows the change in width for each sample.
There was generaltrend for both samples showing that higher temperatures contributed to a larger change in
width. Table 3 shows the calculated fracture toughness, Kc. Figure 1 shows the plot of impact energy as a
function of temperature. Between 50ºF to -25 ºF, the impact of energy of steelwas found to sharply decrease
from 33 ft-lbs to 15 ft-lbs. This displays a textbook ductile-brittle transition temperature, DBTT, in the steel
samples. However this phenomena is absent in the aluminum samples. Figure 2 supports the DBTT in steel
because starting from 50ºF, the % shear lip, decreases from 40% to 20%. The amount of % shear lip in carbon
steel decreased sharply around the DBTT zone. Figure 3 displays the data from table 3 in graphical form. Figure
4 shows the relationship between the fracture toughness and temperature. Steelhas higher fracture toughness
values compared to aluminum, however both alloys were unaffected by temperature.
3. Table 3. Calculated fracture toughness fromthe thicknessof the samples.
Thickness
(mm)
Kc
(MPa*m0.5)
Aluminum 0 9.46 67.23
Aluminum 1 9.46 67.23
Aluminum 2 9.46 67.23
Aluminum 3 9.47 67.26
Aluminum 4 9.46 67.23
Steel 0 9.50 101.05
Steel 1 9.49 101.00
Steel 2 9.50 101.05
Steel 3 9.47 100.90
Steel 4 9.48 100.95
Figure 1. Relationship between the measured impact energy and temperature.
0
5
10
15
20
25
30
35
-150 -100 -50 0 50 100 150 200 250
ImpactEnergy(ft-lbs)
Temperature (ºF)
Impact Energy vs. Temperature
Aluminum
Steel
4. Figure 2. Relationship between estimated shear lip % and temperature
Figure 3. Relationship between average change of width and temperature
0
10
20
30
40
50
60
70
80
90
100
-150 -100 -50 0 50 100 150 200 250
ShearLip%
Temperature (ºF)
Shear Lip % vs. Temperature
Aluminum
Steel
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-150 -100 -50 0 50 100 150 200 250
ChangeinWidth(mm)
Temperature (ºF)
Change in Width vs Temperature
Aluminum
Steel
5. Figure 4. Relationship between fracture toughness and temperature
Figure 5. Charpy Impact Energy vs. Temperature for various metals and alloys.
0
20
40
60
80
100
120
-150 -100 -50 0 50 100 150 200 250
FractureToughness(MPam0.5)
Temperature (ºF)
Fracture Toughness vs. Temperature
Aluminum
Steel
6. Sample Calculations
𝐷 =
1
(2𝜋)
∗ (
𝐾𝐶
𝜎 𝑌𝑆
)
2
Eqn 1. Fracture Toughness Formula
D is the sample width, and σYS is the material tensile yield strength (40ksi for 6061 Al, 60ksi for 1018 Steel).
9.46 =
1
2𝜋
∗ (
𝐾𝐶
40 ∗ 6.894
)
2
𝐾𝑐 = 67.23 𝑀𝑃𝑎 ∗ 𝑚0.5
Conclusion
The Charpy impact test was used to determine the mechanical properties of 6061 Aluminum and 1018
Carbon Steel. By testing for impact energy with regards to sample temperature and through measurement and
visual inspection of the samples, it was possible to surmise information about the ductility/brittleness of the
samples. It was also possible to include an estimation of the Ductile-Brittle Transition Temperature (DBTT) for
the steelsample.
The steel samples show very low impact energy while at low temperatures. It increases dramatically
until ~50°F before leveling out, similar to the error function. This behavior is similar to the published DBTT
curves.
However,even when assuming that the steel sample would follow the trend of leveling out at low
temperature,its exact location of the DBTT is unknown. The data shows a strong point of interest when nearing
0°F; however, it is important to note that this estimate would be largely improved by increasing the temperature
resolution near this area in order to best see where the point of inflection occurs.
The aluminum shows nominal change in impact energy in relation to temperature. This agrees with the
existing literature, and it is safe to assume that the aluminum samples have this behavior due to its FCC structure
(FCC structures will remain ductile at low temperatures3
). Elongation vs. temperature data supports the notion
that aluminum sample do not to have a correlation between elongation and temperature.
The samples were visually inspected to determine shear lip %, which was used to calculate the fracture
toughness, KC. However,human error has to be accounted for when calculating fracture toughness because shear
lip% was determined by visual inspection. The fracture toughness of both materials were unaffected by
temperature.
7. References
1. Rainer Schwab. "Charpy Impact Test." YouTube. Karlsruhe University of Applied Sciences,
26 Jan. 2013. Web. 14 Sept. 2015.
2. TT, H., "THE IMPORTANCE OF THE IMPACT TEST," SAE Technical Paper 150018, 1915,
doi:10.4271/150018. H.A. ELLIOTT.
3. Richard W. Hertzberg, Deformation and Fracture Mechanics of Engineering Materials
4th ed. 1996. p378
4. “Ductile-to-brittle transition.” University of Cambridge.
http://www.doitpoms.ac.uk/tlplib/BD6/ductile-to-brittle.php
