ME 461: Materials Science
Lab Manual
Lab Experiment 2 – Tensile Testing of Metals
Objective
Objective of this study is to obtain the engineering stress-engineering strain
curves for steel, cast iron, and aluminum materials under tensile loading. From the
obtained curves, the important mechanical properties of these materials can be
determined, such as modulus of elasticity (Young’s Modulus), Yield Stress, Tensile
Strength, ductility (percent elongation or percent area reduction) and so on. In addition,
the experiment can be expanded to investigate the effects of the strain rate on the
mechanical properties of metals.
Materials
 Aluminum (Alloy 2024-T351).
 Steel 1020 (Hot Rolled Steel ASTM-A36),
 Cast iron (Gray-20)
Extensometer
moving grip
Gage Length
2in
Equipment
Instron testing machine, extensometer (shown in
Fig.1) and the data acquisition software (Merlin) are
equipped in the laboratory.
close
Fixed grip
Background
Full knowledge of the operation of the Instron
testing machine and familiarity with safety
precautions to stop the machine promptly in an
emergency situation, are required. Please review
tensile testing of materials, the engineering stressstrain curve, and the mechanical properties of
materials in your textbook (Chapter 6).
Procedure
1. Instron extensometer shown in Fig.1 has a
gage length of 2 inches. Use a pen marker to
mark the middle 2-inch span of the specimen’s
close
(Fig.2a) narrow section to specify where to
mount the arms of the extensometer. Measure
the diameter of the narrow section using a Fig.1. Instron testing machine
micrometer and record it in the test table given at which the specimen is
installed and attached with the
at the end.
2. Input the data (material name, displacement extensometer.
rate, gage length, diameter, and geometry of
the specimen) of the test into Merlin software.
3. Install the test specimen in the Instron machine.
4. Mount the extensometer on the specimen. Conduct five tests considering the test
matrix given in Table.1.
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ME 461: Materials Science
Table.1. Testing Matrix
Material
Displacement
Rate (mm/min)
Al2024
5
Al2024
50
HR Steel
5
HR Steel
50
Cast Iron
5
Lab Manual
Extensometer
Remove after 10%
Do not mount
Remove after 10%
Do not mount
Remove after 0.3%
(a)
100 mm
254mm
mm
(b)
Fig.2. Specimen (a) before testing, (b) after testing.
After Test
1. Remove the fractured test specimen from the grips and measure the final gage
length on the specimen. Also, measure the diameter of the specimen at the
fracture (the neck).
2. Calculate the elastic modulus. Determine the yield point, the ultimate tensile
strength, the percentage elongation, and the reduction in area for each of
specimens. Compare material constants of steel, aluminum and iron.
3. Compare the results you obtain with different speed to see the displacement rate
effect on the material properties for aluminum and steel.
Review Questions on Tensile Testing of Metals:
1. What divides the engineering stress-strain curve into two regions, namely, the
elastic and plastic regions?
2. What is the difference between the behavior of the material in the elastic and
plastic regions of the engineering stress-strain curve?
3. What measurement should you have taken in order to be able to plot the true
stress-true strain curve?
4. Why does low carbon steel have clear upper and lower yield points? Why
doesn't the aluminum have the same? Explain the differences using your
knowledge of the alloying and dislocation theories.
5. Did you observe parallel lines inclined about 45o with the horizontal on the
surface of the steel specimen, and in the area where necking later took place?
What are those lines called? What do they reveal about the mechanism of
deformation? Apply Schmid's Law.
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ME 461: Materials Science
Lab Manual
6. Could you observe any similar lines on the aluminum specimen? What is the
mechanism of deformation in this latter case?
7. Obtain the area under the load-extension curve (i.e., energy) for each
specimen and divide it by the volume between the gage length in order to
obtain the modulus of toughness. Compare the value of plain carbon steel and
that of aluminum. Can you draw any conclusion?
8. Looking at the curve indicating the distribution of elongation along the gage
length, where did the maximum localized elongation take place?
9. How do you interpret the shape of the above-mentioned curve?
10. What effect does the high strain rate have on the mechanical properties
mentioned below?
 Modulus of elasticity
 Yield stress
 Ultimate tensile strength
 Elongation percent
 Modulus of toughness
11. Did the high strain rate have an effect on the mode of failure of any of the
specimen? Why?
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ME 461: Materials Science
Lab Manual
Table 2. Test Data
Date
Displacement Rate
Material
Extensometer
Specimen Number
Data File Name
Diameter
Notes
Gage
Length
initial
Final
Initial
Final
Date
Displacement Rate
Material
Extensometer
Specimen Number
Data File Name
Diameter
Notes
Gage
Length
initial
Final
Initial
Final
Date
Displacement Rate
Material
Extensometer
Specimen Number
Data File Name
Diameter
Notes
Gage
Length
initial
Final
Initial
Final
Date
Displacement Rate
Material
Extensometer
Specimen Number
Data File Name
Diameter
Notes
Gage
Length
initial
Final
Initial
Final
Date
Displacement Rate
Material
Extensometer
Specimen Number
Data File Name
Diameter
Notes
Gage
Length
initial
Final
Initial
Final
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