Group 2 Members: Devin Gatherwright, Dylan Terry,
Drew Williams, Travis Watts
Date: 10/17/2012
Course: Materials Science
Materials Science Lab 3: Impact Testing
Introduction
For our third materials science lab, we conducted a Charpy V-notch impact test for both a frozen and
warm 1020 steel rod using a Charpy testing machine, which, in the case of this particular lab, was a
heavy pendulum with a knife edge. According to the materials science textbook, a Charpy test is used to
measure the impact energy of a material. In a Charpy test, the material specimen in question is bar
shaped with a square cross section. Inside the square cross section of the material specimen, a V-notch
is machined. A blow then is applied from a heavily weighted pendulum that is released from a cocked
position at a certain fixed height. When the heavy pendulum is released from its fixed position, the knife
edge mounted on the pendulum swings down, strikes, and fractures the specimen material, which is
secured horizontally on the base of the pendulum. After the fracture, the pendulum continues to swing,
rising to its maximum height. According to the materials science textbook, the impact energy can then
be calculated from the difference between the fixed height and maximum height of the pendulum.
According to the materials science textbook, a Izod impact test is very similar to that of a Charpy impact
test except for how the specimen is supported during the test. In an Izod impact test, the specimen
material is placed vertically in the support whereas the in a Charpy impact test, the specimen material is
placed horizontally in the support.
Objective
The objective of this lab was to gain experience in conducting a Charpy V-notch impact test for both a
frozen and warm 1020 steel rod using a heavy pendulum equipped with a knife edge provided in the
metallurgy lab. Also, to be able to characterize and contrast the mechanical behavior of each material
based on the results both observed and computed in lab.
Procedure
For each material repeat the following steps
• Designate a person as the "operator" of the Charpy test machine: all other persons must
stand clear during testing.
• Designate a person as the "monitor and recorder" of temperatures and impact energies.
• Designate a person as the "test specimen loader" who will remove test specimens, quickly placing
them on the test fixture of the Charpy testing machine.
Use the following procedure to conduct tests in the order shown after exposure to the preconditions to
give the approximate test temperatures indicated:
Room temperature (72 °F)
Freezer (10 °F)
Oven (750 °F)
Place the thermocouple probe in the appropriate medium being sure to allow both the test specimens
and the thermocouple to equilibrate for at least five minutes prior to testing.
• Record the indicated temperature
• "Cock" the pendulum by activating the "raise" mechanism and stand clear while the pendulum is held
in the "cocked" position.
• Using the tongs, quickly remove the test specimen from the medium and place it on the test fixture
with the notch opening facing away from the direction of the cocked pendulum
• Stand clear
• Release the pendulum
• Secure the pendulum in its rest position (i.e., hanging vertically) and retrieve the fractured specimen
halves.
• Record the impact energy (read directly from the dial on the Charpy testing machine)
• Repeat these steps for the each temperature and each material.
Results
Measurements of specimen material measured in lab:
Length (inches)
2.512 in.
Avg. Width (inches)
.377 in.
Notch Width (inches)
.120 in.
Notch Depth (inches)
.054 in.
Measurements of specimen material given in lab PDF file:
Length (inches)
2.510 in.
Avg. Width (inches)
0.378 in.
Notch Width (inches)
.45 in.
Measurements of the pendulum used for the Charpy V-notch test in lab:
Notch Depth (inches)
.045 in.
Pendulum Impact Vel.
17 Jt/s
Mass (lbs.)
66.6 lbf
H1 (inches)
4.51 in.
H2 (inches)
5 in.
Table containing impact energy for 1020 steel specimen
Temperature 0F
720F
7500F
100F
Impact Energy (ft. lb) – 1020
Steel: Machine
215 lbf
229 lbf
182 lbf
Impact Energy (ft. lb) –
1020 Steel: Calculated
272.616 lbf
272.616 lbf
272.616 lbf
Unused energy after
fracture
57.62 +
43.62 +
90.62 +
According to matweb.com, a Charpy impact test for a 1020 steel specimen at 500F (which is as close to
750F as their list gets) should yield a Charpy impact energy of 17.7 lbf, which is not remotely close to
either of the impact energies we observed and calculated for lab. Furthermore, according to
matweb.com, a Charpy impact test for a 1020 steel specimen at 3020F (which is as close to 7500F as the
list gets) should a Charpy impact energy of 50.2 lbf, which again, is not close to either of impact energies
we observed and calculated for lab. Lastly, according to matweb.com, a Charpy impact test for a 1020
steel specimen at 220F (which is as close to 100F as the list gets) should yield a Charpy impact energy of
12.5 lbf, which again, is not close to the either of the impact energies we observed or calculated for this
particular lab.
When the cold 1020 steel bar underwent the Charpy impact test, there was a clean break in the material
where the knife edge struck the V-notch. Also, if you look at the unused energy of the pendulum after
the fracture occurred, you notice that the pendulum has a rather large amount of unused energy.
Inversely, when the warm 1020 steel bar underwent the Charpy impact test, the material fractured, but
it wasn’t as clean of a break as the cold 1020 steel bar. Also, in comparison to the cold 1020 steel bar,
the unused energy after fracture for the warm steel bar was considerably lower.
The following picture is of the cold, brittle 1020 steel specimen. Please note the clean break through the
material:
In contrast, the following picture is of the warmer, ductile 1020 steel specimen. Please note that the
material was not completely fractured in to two separate pieces. Also note the macroscopic plastic
deformation at the fracture area:
The following graph plot demonstrates these relationships between the temperatures and the impact
energies of the specimens much more clearly, with the Y-Axis being the impact energy and the X-Axis
being the temperatures:
Impact Energy VS Temperature
800
700
600
500
400
Impact Energy VS
Temperature
300
200
100
0
72
750
10
To calculate the impact energy, you multiply the mass of the pendulum by the difference between the
fixed height of the pendulum and maximum height the pendulum reaches when it is swung. Hence the
formula :
𝐼𝑚𝑝𝑎𝑐𝑡 𝐸𝑛𝑒𝑟𝑔𝑦 = 𝑊(ℎ1 − ℎ2 )
The following is an example of how the formula would be applied in this lab:
66.6 𝑙𝑏𝑓 (4.5 𝑖𝑛. −5 𝑖𝑛. ) = 272.616 𝑙𝑏𝑓
To find the unused energy of the pendulum, you simply subtract the impact energy reading on the
machine scale from the calculated impact energy figure found above. Here is an example:
272.616 𝑙𝑏𝑓 − 215 𝑙𝑏𝑓 = 57.62 + 𝑜𝑓 𝑢𝑛𝑢𝑠𝑒𝑑 𝑒𝑛𝑒𝑟𝑔𝑦.
Discussion
Based on our observations during the Charpy impact test of the two 1020 steel specimens during lab, as
well as the given information observed and measured in another Charpy impact test that was similar to
the one we conducted, we as a group would say that 1020 steel specimen exposed to the cold
temperatures was very brittle and very susceptible to fracture. We as a group would also say that the
1020 steel specimen exposed to warmer temperatures was more ductile in nature, as well as being
more resistant to fracture. When observing the cold 1020 steel specimen after the Charpy impact test
was conducted, we as a group noticed that the cold 1020 steel specimen had a clean break straight
through the middle, meaning there was no noticeable macroscopic plastic deformation that we could
see. Also, the fracture surface for the cold 1020 steel specimen was perfectly flat, which is another
hallmark of a typical brittle fracture. Inversely, when observing the warmer (I’d say near room
temperature) 1020 steel specimen after the Charpy impact test was conducted, we noticed that the
warm 1020 steel specimen did not have a clean break through the material like the cold 1020 steel
specimen did. Instead, the fracture was more jagged in nature, meaning the fracture had noticeable
macroscopic plastic deformation, which is a typical hallmark of a ductile fracture. These observations
made during lab seemed to match up with the given information from a previous Charpy impact test.
When looking at the given information, we noticed that the impact energy exerted upon the cold 1020
steel specimen by the pendulum was relatively low, while the unused energy of the pendulum after
fracture was relatively high. Inversely, the impact energy exerted upon the warm 1020 steel specimen
by the pendulum was considerably higher than that of the cold 1020 steel specimen, while the unused
energy of the pendulum after fracture for the warm 1020 steel specimen was considerably lower than
that of the cold 1020 steel specimen. So, based on these observations and figures, we as a group would
say that a brittle material is more susceptible to fracture than a ductile material. It should also be stated
that the figures given contained another Charpy impact test for a 1020 steel specimen with an elevated
temperature. When looking at the figures for the hot 1020 steel specimen, we as a group noticed that
the impact energy was higher than both the warm and cold steel specimens, while the unused energy of
the pendulum was lower than both the warm and cold steel specimens. So, based on these figures, we
as a group would assume that a highly ductile metal takes more impact energy to be fractured, whereas
a brittle metal takes less impact energy.
When comparing the impact energies of the three different temperature 1020 steel specimens for this
lab to the listed impact energies for 1020 steel specimens on matweb.com, we as a group noticed that
the impact energies were very different from each other. For example, for the cold steel specimen, the
impact energy listed in this lab by the machine was 182 lbf, while the listed impact energy for a similar
cold 1020 steel specimen was 12 lbf, which is a glaring difference. We as a group assume that these vast
differences could be attributed to different Charpy impact testing equipment. For example, the
pendulum used for the matweb.com Charpy impact test of the 1020 steel specimens might have more
mass than the pendulum we used in lab for our Charpy impact test. Also, the fixed height set for the
pendulum used for the matweb.com Charpy impact test of the 1020 steel specimens might have been
greater than that of the fixed height we used in lab for our Charpy impact test. Lastly, the maximum
height the pendulum reached after fracture during the matweb.com Charpy impact test for the 1020
steel specimens might have been greater than the maximum height the pendulum we used in lab
reached after the fracture of the material. So, in short, there are a number of explanations for the vast
difference in impact energies when comparing our labs results to those listed on matweb.com.
Conclusion
From this lab, we as a group have learned how to properly conduct a Charpy Impact V-notch test using a
heavy pendulum equipped with a knife edge in order to fracture a specific specimen. We also learned
both the similarities and differences between and Charpy impact test and an Izod impact test. We
learned that both the Charpy and Izod impact tests are conducted in the exact same way, except for
how the specimen is supported in each test. We learned that in a Charpy impact test, the specimen is
secured horizontally on the base while in an Izod impact test, the specimen is secured vertically on the
base. We also learned that how to properly calculate the impact energy exerted the specimen material
by using the formula 𝑊 = (ℎ1 − ℎ2 ), with W being the mass of the pendulum in lbf; h1 being the fixed
height of the pendulum before it is swung; and h2 being the maximum height that the pendulum reaches
when it is swung. We also learned that 1020 steel becomes very brittle when subjected to low
temperatures, but is very ductile at elevated temperatures. Lastly, from this lab, we as a group learned
that a brittle material will be more susceptible to fracture and will also show no macroscopic plastic
deformation, whereas a ductile material will be more resistant to fracture and will show signs of plastic
deformation at a macroscopic level.
Contributions



Devin Gatherwright: wrote the introduction and objective of the lab report; contributed to the
discussion and conclusion of the lab report; and compiled the lab report and lab report data.
Travis Watts: contributed the formulas and to the discussion and conclusion of the lab report.
Drew Williams: created the Temperature Vs. Impact Energy plot for the 3 1020 steel specimens
and contributed to the discussion and conclusion of the lab report.

Dylan Terry: contributed the pictures and to the discussion and conclusion of the lab report.
Works Cited
Matweb.com. Matweb.com. Information retrieved from http://www.matweb.com/