Experiment 4 - Testing of Materials in Tension Object: The object of this experiment is to measure the tensile properties of two polymeric materials, steel and aluminum at a constant strain rate on the Tension testing machine. Background: For structural applications of materials such as bridges, pressure vessels, ships, and automobiles, the tensile properties of the metal material set the criteria for a safe design. Polymeric materials are being used more and more in structural applications, particularly in automobiles and pressure vessels. New applications emerge as designers become aware of the differences in the properties of metals and polymers and take full advantage of them. The analyses of structures using metals or plastics require that the data be available. Stress-Strain: The tensile properties of a material are obtained by pulling a specimen of known geometry apart at a fixed rate of straining until it breaks or stretches to the machines limit. It is useful to define the load per unit area (stress) as a parameter rather than load to avoid the confusion that would arise from the fact that the load and the change in length are dependent on the cross-sectional area and original length of the specimen. The stress, however, changes during the test for two reasons: the load increases and the cross-sectional area decreases as the specimen gets longer. Therefore, the stress can be calculated by two formulae which are distinguished as engineering stress and true stress, respectively. (1) = P/Ao= Engineering Stress (lbs/in 2 or psi) P = load (lbs) Ao= original cross-sectional area (in 2) (2) T= P/Ai = True Stress Ai = instantaneous cross-sectional area (in 2) Likewise, the elongation is normalized per unit length of specimen and is called strain. The strain may be based on the original length or the instantaneous length such that (3) =(lf - lo)/ lo = l / lo = Engineering Strain, where lf= final gage length (in) lo= original gage length (in) (4) T= ln ( li / lo ) = ln (1 +) = True Strain, where li = instantaneous gage length (in) ln = natural logarithm For a small elongation the engineering strain is very close to the true strain when l=1.2 lo, then = 0.2 and T= ln 1.2 = 0.182. The engineering stress is related to the true stress by (5) T= (1 + ) The true stress would be 20% higher in the case above where the specimen is 20% longer than the original length. As the relative elongation increases, the true strain will become significantly less than the engineering strain while the true stress becomes much greater than the engineering stress. When l= 4.0 lo then  = 3.0 but the true strain =ln 4.0 = 1.39. Therefore, the true strain is less than 1/2 of the engineering strain. The true stress (T) = (1+ 3.0) = 4, or the true stress is 4 times the engineering stress. Tensile Test Nom ...

1. Experiment 4 - Testing of Materials in Tension
Object: The object of this experiment is to measure the tensile
properties of two polymeric
materials, steel and aluminum at a constant strain rate on the
Tension testing machine.
Background: For structural applications of materials such as
bridges, pressure vessels, ships,
and automobiles, the tensile properties of the metal material set
the criteria for a safe design.
Polymeric materials are being used more and more in structural
applications, particularly in
automobiles and pressure vessels. New applications emerge as
designers become aware of
the differences in the properties of metals and polymers and
take full advantage of them. The
analyses of structures using metals or plastics require that the
data be available.
Stress-Strain: The tensile properties of a material are obtained
by pulling a specimen of

2. known geometry apart at a fixed rate of straining until it breaks
or stretches to the machines
limit. It is useful to define the load per unit area (stress) as a
parameter rather than load to
avoid the confusion that would arise from the fact that the load
and the change in length are
dependent on the cross-sectional area and original length of the
specimen. The stress,
however, changes during the test for two reasons: the load
increases and the cross-sectional
area decreases as the specimen gets longer.
Therefore, the stress can be calculated by two formulae which
are distinguished as
engineering stress and true stress, respectively.
2 or psi)
P = load (lbs)
Ao= original cross-sectional area (in
2)
Ai = instantaneous cross-sectional area (in
2)

3. Likewise, the elongation is normalized per unit length of
specimen and is called strain. The
strain may be based on the original length or the instantaneous
length such that
-
lf= final gage length (in)
lo= original gage length (in)
li = instantaneous gage length (in)
ln = natural logarithm
For a small elongation the engineering strain is very close to the
true strain when l=1.2 lo,
related to the true stress by
The true stress would be 20% higher in the case above where
the specimen is 20% longer
than the original length. As the relative elongation increases,

4. the true strain will become
significantly less than the engineering strain while the true
stress becomes much greater than
strain =ln 4.0 = 1.39.
Therefore, the true strain is less than 1/2 of the engineering
Tensile Test Nomenclature: The tensile test data are
characterized by terminology shown in
Figure 4-1.
The material test curves have a region where the deformation
caused by the stress is elastic,
or not permanent. This means when the stress is removed the
specimen returns to its original
length. At stresses greater than a certain value, a portion of the
strain becomes permanent or
plastic. The stress required to cause a 0.2% plastic strain, or
off-set, is called the yield stress.

5. Ductility is measured as % elongation, representing the ability
to deform in the plastic range
(6)
100%
0
0
l
ll
elongation
f
Equipment

6. United Tensile Testing Machine: floor-mounted (20,000 lb.
capacity)
Calipers, Ruler
Procedure
You will receive 4 specimens (high density polyethylene, low
density polyethylene, steel and
aluminum.
Using calipers measure (in the reduced area):
1) the thickness of the specimen to +.002 inches.
2) the width of the specimen to + 0.02 inch.
Make sure to record the specific metal alloy, original specimen
width, thickness, gage length;
and after fracture load and percent elongation (total strain).
Place the specimen as instructed and tighten the clamps
securely. The original crosshead
distance (gage length) will be measured with a ruler after the
sample has been placed firmly
in the grips. The gage length is the distance from the top of the
lower clamp to the bottom of

7. the upper one. Measure the gage length to + 0.1 inch.
MSE 227 LAB – Tensile Machine Operation
Click on DATUM shortcut on the Desktop (wait for program to
finish loading)
Click on Template for:
- testing rate will be 0.2
inch/minute
- testing rate will be 2.0
inch/minute
Click on SAMPLE INFORMATION tab:
Enter
(Make sure to ENTER the information, so that it calculates the
Area correctly)
The CONTROL SEGMENT tab shows the testing rate for the
given set up.
Tighten the grips on the sample; you can see the force you are
applying on the computer screen.

8. You want to be sure the grips are secure (hopefully with no
more than 5lb force preload).
Click on TEST when ready to begin testing.
Make sure to record test number, so you can find your data.
Click on REPORT to Export your file.
To retrieve data go to:
Glossary of Terms
Understanding the following terms will help in understanding
this experiment:
Ductility - The ability of a material to be permanently deformed
without breaking when a force is
applied.
Elastic deformation - Deformation of the material that is
recovered when the applied load is

9. removed. This temporary deformation is associated with the
stretching of atomic bonds.
% Elongation - The total percent increase in the length of a
specimen during a tensile test.
Engineering strain - Increase in sample length at a given load
divided by the original (stress-free)
length.
Engineering stress - The applied load, or force, divided by the
original cross-sectional area of the
material.
Engineering stress-strain curve - A plot of the Engineering
stress versus the Engineering strain.
Hooke's law - the linear relationship between stress and strain
in the elastic portion of the stress-
strain curve.
Modulus of elasticity - Young's modulus, or the slope of the
stress-strain curve in the elastic region.
Necking - Local deformation of a tensile specimen. Necking
begins at the tensile point.
Offset yield strength - yield strength obtained graphically that
describes the stress that gives no more
than a specified amount of plastic deformation.
Plastic deformation - Permanent deformation of the material

10. when a load is applied, then removed.
% Reduction in area - The total percent decrease in the cross-
sectional area of a specimen during the
tensile test.
Tensile strength - The maximum engineering stress experienced
by a material during a tensile test
(ultimate tensile strength).
Tensile test - Measures the response of a material to a slowly
applied uniaxial force. The yield
strength, tensile strength, modulus of elasticity, and ductility
are obtained.
True strain - The actual strain produced when a load is applied
to a material.
True stress - The load divided by the actual area at that load in
a tensile test.
Yield strength - The stress applied to a material that just causes
permanent plastic deformation.
Write Up
Prepare a memo report on the results of the tests. The report
should contain 4 Figures
(graphs) that contain an overlay of engineering and true stress-
strain curves from the

11. tensile tests for each material. All graphs should be graphed
using Excel. Label engineering
curves to show Young's Modulus, Yield Stress, Ultimate Tensile
Strength, and Total
Strain (also label values; for example, Young’s modulus =
41000 psi). Discuss these values
in your report and compare them with published values for the
same alloys. Discuss your
4 graphs, the errors involved in this experiment and their
sources.
References
McClinock, Mechanical Behavior of Materials
Dieter, Mechanical Metallurgy
Nielsen, Mechanical Properties of Polymers
MSE 227L Name ________________________
Testing of Materials in Tension
Poor Fair Average Good Excellent
Memorandum Format Used 1 2 3 4 5

12. Spelling, grammar & punctuation correct 1 2 3 4 5
Report includes: Poor Fair Average Good Excellent
Compare graphs for engineering stress-
engineering strain, and true stress-true strain
using data from tensile tests for each material
(4 graphs total; 2 curves overlaid per graph).
4 8 12 16 20
Label Engineering Curves only
Young's Modulus labeled neatly using Excel
(Include values on graph). Show calculations.
1 2 3 4 5
Yield Stress labeled neatly using Excel
(Include values on graph).
1 2 3 4 5
Total Strain labeled neatly using Excel
(Include values on graph).
1 2 3 4 5
Ultimate Tensile Strength labeled neatly

13. using Excel (Include values on graph).
1 2 3 4 5
elongation compared to published values.
Include table with compared values and
measured data.
2 4 6 8 10
Discussion of errors in this experiment and
their sources.
1 2 3 4 5
Poor Fair Average Good Excellent
Overall level of effort apparent 1 2 3 4 5
Quality of graphs 1 2 3 4 5
Quality of Abstract 1 2 3 4 5
Quality of work description 1 2 3 4 5
Quality of conclusions 1 2 3 4 5

14. Theory
After carrying out tensile tests, the various material properties
can be calculated by the respective formulas. This is achieved
by use of engineering formulae related to stress and strain
Stress can be calculated using the formula below. This is
engineering stress
Where;
Where;
Where;
Elongation
Calculation of elongation the formula used is.
Where
L0=original gauge length
=engineering strain
Lf=final gauge length
Percent elongation
Experimental equipment

15. 1. Vernier callipers
2. Tensile testing machine
3. Computer installed with DOS
Procedure
Visual inspection of the sample was done to locate if there
are any flaws. The lengths of the metals and the polymeric
materials were measured. With the help of the results obtained
for lengths the computer was calibrated to receive data and the
respective graphs were plotted. Steel was clamped in the
machine and the machine was activated the registered values of
force and elongation were recorded. The procedure was repeated
starting from procedure two for aluminium and the other
polymeric materials. The data was tabulated for analysis.
RESULTS
Table 1: results
Specimens
Width (in)
Thickness(in)
Gage length
Area
Aluminum

16. 0.4780
0.1225
3.35
0.058555
Steel
0.1240
0.1240
3.45
0.015376
High density polyethylene
0.727
0.1225
1.30
0.0890575
Low density polyethylene
0.7285
0.1210
1.40
0.0881485
Table 11: other material properties
Specimens
Width (inches)
Thickness (inches)
Cross-sectional area(in2)
After fracture load (lbs.)
Engineering stress(lb./in2)

17. Calculated, Young’s modulus
(Gpa)
Theoretical young’s modulus
(Gpa)
Engineering strain
Theoretical ultimate tensile strength(Mpa)
Aluminum
0.49
0.12
0.0588
3675
62500
94.3
69
0.4566
110
Steel
0.48
0.12
0.0576
4258
73923.6
271
200
0.1876
400
High density polyethylene
0.72
0.12
0.0864
409
4733.79
1.7
0.8
0.1825
60

18. Low density polyethylene
0.74
0.12
0.888
140
157.65
0.5
0.45
1.9791
30
Theoretical properties of steel aluminum and polymeric material
was obtained from ("Modulus of Elasticity or Young's Modulus
- and Tensile Modulus for some common Materials", 2016)
Discussion
Due to different material properties the material fracture at
different rates when subjected to the same loading. In order to
verify the properties of a material test are carried out targeting
different properties of such a material. Tensile test is carried
out to know the tensile properties of such a material. To be able
to compare the material properties of different materials the
dimension of the respective materials used are should be
similar. For this case the thickness of all the material used was
about 0.12 in. The experiment was testing the material tensile of
two metals (aluminum and steel) and two polymeric materials
(low density and high density polymeric). All of the four
materials behaved differently when subjected to same tensile
forces.
Steel and aluminum have different stresses before fracture,
this is because they have different atomic structure properties.
They have high ultimate tensile strength hence they tolerate
large stress before they undergo fracture. Due to stronger
intermolecular forces as a result of fewer branches in its
structure the high density polyethylene has higher ultimate
tensile strength while the low density one has low ultimate
tensile strength because of weaker intermolecular forces. The
low ultimate tensile strength means the material tolerates very

19. small engineering stress to fracture, the material fracture at very
small loading.
All the material tolerates the strain to a certain point
beyond which if any more stress is applied the material neck
and eventually fractures. Necking occurs when there is fast flow
of the length at a point where maximum stress is reached. Due
to high ductility the polymeric experience drawing at this point
after necking, the material necking traverses the entire length of
the material. Stress on the material changes as the materials
strain over time due to increase in the loading and decrease in
the cross-sectional area after necking. The percentage
elongation shows the ductility property of the materials. Low
density polyethylene is most ductile of all the four materials.
For the metals steel is more ductile than aluminum.
The young’s modulus values for all the materials differ because
of the experimental errors, the error may result from estimation
of dimensions of thickness and width. Majorly it is the human
error that cause this difference. The values for ultimate tensile
strength also differ in because of the same errors.
Conclusion
From the experiment has been proved that metals have high
ultimate tensile strength as compared to polymeric materials.
The graph of the stress against strain for the materials obeys
Hooke’s law up to a point where the yield strength is reached,

20. the material undergoes elastic deformation. Beyond this point
the material begins to neck as it cannot contain any more stress
with increasing loading, plastic deformation occurs hence.
Metals show typical failure characteristics, the outer part
experiences shear failure while the middle experiences tensile
failure.
References
Abu-Saba, E. (1995). Design of Steel Structures. Boston, MA:
Springer US.
Askeland, D., Fulay, P., & Wright, W. The science and
engineering of materials.
Modulus of Elasticity or Young's Modulus - and Tensile
Modulus for some common Materials. (2016).
Engineeringtoolbox.com. Retrieved 14 March 2016, from
http://www.engineeringtoolbox.com/young-modulus-d_417.html
Soboyejo, W. (2003). Mechanical properties of engineered
materials. New York: Marcel Dekker.

21. APPENDIX
Alrashaid 1
Alrashaid 2
Alrashaid 3
Theories:
Engineering Stress : σ = P/A0,
True Stress : σ T = P/AT, σ T = σ (1+ ϵ ).
True Stress: ϵ = (lf – l0) / l0.
True train: ϵ t = ln (li/l0) = ln (1+ ϵ).
Precent elongation= ((lf – l0) / l0) *
Precent Error = ((|Experimental Value – Theoretical

22. Value|)/Theoretical Value)*
Modulus of elasticity E = slope of young’s modulus line in
stress vs strain curve
Discussion:
By observing the stress-strain curves the different tensil
properties for the various tested materials can be seen. The
material with the largest ultimate tensile strength is steel shown
in Figure 1. What can be noticed on the curve of this particular
specimen is the the wavey distortions before the curve reaches
the ultimate tensile stress. This is due to the properties of steel
in which some discontinuities within the grain structure and
impurities within the sample are formed which yielded almost
constant strain under the increasing tensile load. This happens
with the aluminun sample but in a lesser manner. Steel also
experiences more necking before failure comparinng it with the
Aluminum sample. It can be cunclueded that Aluminum was
more brittle than steel.Both polymers LDPE and HDPE have a
largees plastic region, which means they deforem a lot more
before faluir accures in comparison with thhe steel and
aluminum sample. This can be seen in figures 3 and 4 The table
below shows all the calculations done that helped in forming the
graphs.
Specimen
Width (in)
Thickness (in)
Area (in^2)
Lo
Lf
%Elongation
Steel 1018
0.503
0.125
0.062875
3.79

23. 4.7050955
24.145
LDPE
0.839
0.129
0.108231
3.75
10.2133125
172.355
Al 2024
0.505
0.127
0.064135
3.75
4.5742125
21.979
HDPE
0.737
0.12
0.08844
3.75
10.3402875
175.741
Fail load (lb)
ENG stress (psi)
Strain (psi)
ENG strain (psi)
True strain
True stress
3985.367
63385.55865
17.14908
0.1714908
0.158277126
74255.59881

24. 152.1301
1405.605603
19.40467
0.1940467
0.177348126
1678.358732
4111.328
64104.28003
20.44067
0.2044067
0.185987081
77207.62437
343.628
3885.436454
12.256
0.12256
0.115611791
4361.635546
Young’s modulus for the matrials was alos calculated. This
was done by taking the slope of young’s modulus line in stress
vs strain curve shown in figures 1, 2, 3, and 4. The calculated
values were campared to the given values and the error was
obtained. The below table shows the results :
Material
Calculated Modulus
Given Modulus
Error %
1018 steel
1940785.802
29000000
93.30764
2024 Aluminum
212019.4049
1000000

25. 78.79806
LDPE
30897.88491
80000
61.37764
HDPE
159807.4659
145000
10.21205
Figures:
Figure 1: Stress-strain curve for 1018 Steel
Figure 2: Stress-strain curve for 2024 Aluminum
Figure 3: Stress-strain curve for LDPE
Figure 4: Stress-strain curve for HDPE