This technical report details an impact test conducted on three types of steel (hot, cold, and steel alloy) using the Charpy method at various temperatures to analyze ductility and brittleness transitions. The experiment determined a ductile-to-brittle transition temperature of around -18°C, with additional insights into the relationship between temperature and material toughness. Despite some experimental errors impacting the results, it was concluded that lower temperatures increase brittleness in mild steel, while higher temperatures enhance ductility.

1. SOKOINE UNIVERSITY OF AGRICULTURE
COLLEGE OF AGRICULTURE
Department of Engineering sciences and Technology
PRACTICAL REPORT
IMPACT TEST TECHNICAL REPORT
Bsc .IRRIGATION AND WATER RESOURCES ENGINEERING
DOTO, MUSA GESE
IWR/D/2016/0011
VENUE: COET-UNIVERSITY OF DAR ES SALAAM
INSTRUCTOR: COET-UDSM
DATE OF SUBMISSION: February,2018

2. ABSTRACT
In the material testing laboratory, a Charpy impact test was performed on three different types
(hot,cold,and steel alloy)of steels testing each variety at four different temperatures (32°C(RT),
100°C,0°C and -22°C ). From results (shown below), we determined that the a transition is
from ductile failures to brittle failures.
specimen
(S)
Impact
toughness
(32o
c)
percent
brittleness
32o
c
Impact
toughness
(100o
c)
percent
brittleness
100 o
c
Impact
toughness
(0o
c)
percent
brittleness
0 o
c
Impact
toughness
(-22o
c)
percent
brittleness
-22 o
c
S1 13 90 176 80 12 30 8 20
S2 202 90 170 90 188 30 66 10
S3 183 90 183 50 184 10 190 20
Impact strength Transition Temperature Ductile-Britle Transition Temperature
-18o
C 16 o
C
Table 1
i

3. Table of content
Abstract
LIST OF FIGURE
ACKNOWLEDGEMENT
1. INTRODUCTION
1.1 The aim of the experiment
1.2Theory of the experiment
2. EXPERIMENTAL METHODS
2.1 Machine and devices used in impact test
2.2 Specimen
3. EXPERIMENTAL PROCEDURE AND PRECAUTIONS
4. RESULTS AND DISCUSSION
4.1 Results
4.2 Discussion
4.3 Sources of error
5. CONCLUSION
REFERENCES
APPENDICES
1. Graph of a graph of impact strength against temperature (˚c)
2. Graph of a graph of average crystalline against temperature (˚c)
3. Table 1: summary of final data from impact test
4. Units conversion and formula
5. List of symbols
ii

4. LIST OF FIGURES
Figure 1: Charpy testing machine
Figure 2: specimen
iii

5. ACKNOWLEDGEMENT
I would like to express my grateful appreciation to the practical coordinator of the department of
engineering science and technology at SUA, PROF. LAZARO for providing a conducive
economic situation that enabled me to travel well without any obstacles to UNIVERSITY OF
DAR ES SALAAM. Also special thanks are directed to UNIVERSITY OF DAR ES
SALAAM management for their kindness for allowing me to conduct my practical at their
university. Last but not least I extend my sincere thanks to the following for their valuable
contributions and advices on completion of my practical; DR. TESHA for his excellence
lecturing of tensile testing of material theories and MR. BURTON for his excellence directives
during the tensile test process.
iv

6. 1. INTRODUCTION
1.1 The aim of the experiment
The aim of the experiment is to determine the transition temperature and examine
variation of ductility with temperature of the mild steel using the impact test machine
(charpy impact test machine) and V-notch square mild steel specimen.
1.2 Theory of experiment
Fracture in materials was widely investigated especially during the industrial revolution
where extraction processes of iron and steels led to the wide-spread uses of iron and
steels for structural and transportation applications, etc. However, metallurgy of iron and
steels was not deeply understood, which resulted in improper utilization of materials.
Moreover, with low engineering technology, defects were normally observed in jointed
metals or assembled parts, which were the main problems leading to weakening and
global failure of engineering structures during services. The well known case has been
the tragic failure of the Liberty ships and T-2 tankers. The Liberty ships built during the
World War II appeared to have cracks along the welds resulting in fracturing into two
halves as they were at the deck prior to services. Brittle fracture has then been
investigated in great details whereas ductile fracture was however studied in a lower
extent due to its less deleterious effects. Since brittle fracture has been one of the most
catastrophic types leading to losses of life and cost, study of brittle fracture especially in
steels has therefore been on the main focus. Investigation into causes and factors
affecting fracture behaviour has been of great interest and solutions to its problems have
also been cooperated.
Charpy impact test is practical for the assessment of brittle fracture of metals and is also
used as an indicator to determine suitable service temperatures. The Charpy test sample
has 10x10x55 mm 3 dimensions(say DIN 50115), a 45o
C V notch of 2 mm depth and a
0.25 mm root radius will be hit by a pendulum at the opposite end of the notch as shown
in figure 1. To perform the test, the pendulum set at a certain height is released and
impact the specimen at the opposite end of the notch to produce a fractured sample. The
absorbed energy required to produce two fresh fracture surfaces will be recorded in the
unit of Joule. Since this energy depends on the fracture area (excluding the notch area),
thus standard specimens are required for a direct comparison of the absorbed energy
1

7. As the pendulum is raised to a specific position, the potential energy (mgh) equal to
approximately 294J is stored. The potential energy is converted into the kinetic energy
after releasing the pendulum. During specimen impact, some of the kinetic energy is
absorbed during specimen fracture and the rest of the energy is used to swing the
pendulum to the other side of the machine as shown in figure 1. The greater of the high
of the pendulum swings to the other side of the machine, the less energy absorbed during
the fracture surface. This means the material fractures in a brittle manner. On the other
hand, if the absorbed energy is high, ductile fracture will result and the specimen has high
toughness. Generally, fracture behaviour of BCC structured metals such as mild steels
varies with temperature. At low temperature, BBC metals fracture in a brittle mode and
becomes more ductile as the temperature increases. FCC structure metals such as
stainless steels, copper and aluminum however do not show a dramatic change in fracture
behaviour with increasing temperature. Therefore, an investigation of fracture behaviour
in BCC structure metals is concerned with the ductile to brittle transition temperature
(DBTT) curve. This curve shows three different regions of lower shelf, upper shelf and
transition region as shown in figure 3. If we first consider fracture surfaces of samples
tested at low temperatures, the brittle fracture surfaces consisting primarily of cleavage
facets and in some cases with small areas of ductile dimple as illustrated in figure 4.
Cleavage fracture requires less energy to produce flat fracture surfaces of the cleavage
facets. As the temperature increases, the area of cleavage facets is reduced as opposed to
increasing regions of ductile dimples or ductile tearing. Within a transition range, the
absorbed energy increases rapidly and the specimen fracture surfaces now show a mixed
mode of ductile and brittle features. The percentage of ductile and brittle features in this
region depends on the test temperatures. The higher the temperature, the more ductile
areas will result. In the upper shelf region according to the DBTT curve, the fracture
surfaces become fully ductile (100% fibrous). The fracture surface appears relatively
rough, dull and gray due to microvoid formation and coalescence. This type of fracture
surface provides the highest energy absorption due to extensive plastic deformation.
2

8. 2. EXPERIMENTAL METHODS
2.1 Machine and devices used in impact test
a) Charpy impact test machine
This machine provides a maximum striking energy of 294 joules
Figure 1
b). Electric heater used to heat the specimens to 100o
C ( boiling point)
c) Thermometer used to measure the temperature of specimen and room temperature
d) Thermos flask, which serves as a containing ice for cooling the specimen
2.2 Specimen
The specimen used is V-notch mild steel specimens (DNI 50115)
figure 2
3

9. 3. EXPERIMENTAL PROCEDURE AND PRECAUTIONS
The following are the experimental procedures involved in performing impact test using charpy
impact test machine
1. Examine standard Charpy impact specimens of 10x10x55 mm3
dimensions with a V
notch of 45o
angle and 2 mm depth located in the middle as shown in figure 2. 2 .Three
of specimens will be tested at individual temperatures (32(RT),100,0 and -22 o
C).
2. Determination of friction losses: releasing the hammer without a specimen inserted, this
should result to zero energy used by the hammer. Any difference is due to friction losses.
Then record the energy due to the friction losses which was 2 J
3. Set up the pendulum up to its original position to have 300J(maximum energy)
4. Placing the specimen in the support at the base of the tester with the notch facing away
from the direction of impact. The first notched bar is at room temperature which was
32˚C.Precaution,make sure the pendulum is tightened strongly to avoid accidentary
falling which may cause body damage.
5. After specimen being well placed and the path of the pendulum swing is clear, release
the hammer by pushing forward firmly on the release handle. The pendulum swings
through and break the specimen in two half. Record the energy consumed from the dial.
6. The data recorded from dial should minus the energy due to friction losses to get the
energy which caused the specimen to break and record it on the table of results as shown
in Table
7. Take the fractured specimen and observe the degree of crystalline on the fracture to
determine the percentage of brittleness of the fracture at that temperature. Then record it
on the table of results
8. Do the same procedures with the specimen of the same temperature 100˚C,0˚C and -22˚C
to obtain three recordings of energy required for fracture and percentage of brittleness,
Take precautions for hot and cold specimens
9. Repeat the second step up to the last one for the mild steel with temperatures of 100˚C,
0˚C and -22˚C and the data are represented in table of results as shown in Table
10. Plot the graph of average crystalline against temperature (˚c) and the graph of impact
strength against temperature (˚c) .Give conclusions
4

10. 4. RESULTS AND DISCUSSION
4.1 Results
Energy loss due to friction is 2 joules
Area of the V-notch specimen is 0.8cm2
Temperature
in o
C
energy consumed in
Joule
Average
energy in
Joule
impact strength
in j/cm2
S1 S2 S3
100 176 170 183 176.3 220.375
32 13 202 183 133.7 167.125
0 12 188 184 128 160
-22 08 66 190 88 110
Table 2:Table of Results
Temperature
(˚C) Percentage of brittleness (%)
Average
percentage of
brittleness (%)
100 80 80 50 70
32(RT) 90 90 90 90
0 30 30 10 23.33
-22 20 40 20 26.67
Table 3: percentages of brittleness at different temperatures
4.2 Discussion
The transition temperature from the graph of the impact strength against temperature and
that of percentage of brittleness against temperature are not the same because there was
an error which was caused by the loss of temperature of the specimen when transferring it
from the heater to the charpy machine and when delaying placing the specimen on the
machine.
5

11. 4.3 Sources of error
 Zero error of the machine (friction losses)
 Parallax error when reading the value of energy
 Human error in data analysis
5. CONCLUSION
Although the transition temperature being different from the graph of impact strength against
temperature and the graph of average percentage of crystalline against temperature, we can still
conclude that the graph of the impact strength against temperature proves the theory that ductility
of the material varies with the temperature and it shows that the material is more ductile at high
temperatures and more brittle at low temperature.
Also the graph of percentage of crystalline against temperature show that the percentage of
brittleness of the fracture increases as the temperature decrease this conclude that ,the mild steel
becomes brittle at low temperature and it becomes ductile at high temperature.
6

12. REFERENCES
Kabyemera, I.; Kolasa, A and Bisanda, E.T.N. Laboratory Practicals in Materials Technology.
Department of Mechanical Engineering Manuscript, University of Dar es salaam, 1993.
Callister, Jr, W.D. Material Science and Engineering: an Introduction, 5th edition, 2000
7

13. APPENDICES
1. Graph of a graph of impact strength against temperature (˚c)
2 Graph of a graph of average crystalline against temperature (˚c)
8

14. 3 Table 1: summary of final data from the impact test
specimen
(S)
Impact
toughness
(32o
c)
percent
brittleness
32o
c
Impact
toughness
(100o
c)
percent
brittleness
100 o
c
Impact
toughness
(0o
c)
percent
brittleness
0 o
c
Impact
toughness
(-22o
c)
percent
brittleness
-22 o
c
S1 13 90 176 80 12 30 8 20
S2 202 90 170 90 188 30 66 10
S3 183 90 183 50 184 10 190 20
Impact strength Transition Temperature Ductile-Britle Transition Temperature
-18o
C 16 o
C
4 UNITS CONVERSION AND FORMULA
1cm2
= 100mm2
U = mg(H-h)
V = √
at = Af/A
5. LIST OF SYMBOLS
Symbol Definition
A Area of specimens (cm2
)
Cm Centimeter
o
C degree of temperature in celicius
J Joule
RT Room Temperature
DBTT Ductile to brittle transition temperature
BCC body centered cubic
FCC Face centered cubic
M mass
G Acceleration due to gravity
H height
DBTT Ductile to brittle transition temperature
UDSM University of Dar es salaam
9