Lab3
pdf
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University of Central Oklahoma *
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Date
Dec 6, 2023
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University of Central Oklahoma
Slender Column Test - Experiment 3
Dylan Robinson, Joshua Jackson, and Kaleb Paddock
Dr. Adnan Al-Ibadi
Thursday 1:00 PM
10/6/22
Abstract
Experiment 3 for the Strength of Materials laboratory covers a test of a
slender column. In this experiment, the slender column specimen is loaded into
the testing apparatus (Universal Testing Machine or ZPM) and an axial force is
applied to the specimen. In this particular experiment, we are asked to calculate
a theoretical value for the maximum axial load that can be applied before the
specimen is pushed beyond a point where it can return to its original state. This
experiment employs many of the concepts that we are familiar with from the
lecture portion of the Strength of Materials class, and this experiment works to
improve our understanding of those concepts.
In civil engineering columns are used to support various structures. These
structures can impose tremendous loads on the columns. In slender columns,
sometimes loading can reach a point of near failure. At this point any variance in
forces on the slender column causes it to buckle.[1]
Machines and Instruments
‘Image 1’ shows the main machine use
d in this experiment. This machine
applies an accurate and measured force onto our test specimen, as well as
measures the displacement of the specimen due to the force applied. This ZPM
is different from the standard equipment and is the same test stand utilized in the
previous experiment, the Tension Test. Using this information, we are able to test
our theoretical value for the critical force applied before the specimen cannot
return to its original stage, against a value we obtain during the experiment.
Experimental Method
In this experiment, we rely heavily on the concepts of stress, strain,
modulus of elasticity, and a few other key concepts specific to strength of
materials.
A tensile test was conducted on an aluminum specimen using the ZPM
described above. The data points for the precise force being applied as well as
displacement measured in the specimen was recorded.
Our role in utilizing the test stand was fairly limited. The Lab assistant
ensured the test equipment was calibrated as well as conducting the operation of
the test stand. After the specimen was tested, the data was aggregated and an
analysis was organized.
Image 1: Specimen Loaded into the secondary testing machine.
Test Procedure
This procedure assumes the ZPM has been set up and calibrated.
The test specimen is composed of Aluminum, which is helpful information
for finding the modulus of Elasticity. The specimen has two cylindrical cuts at
either end in order to mount the specimen into the testing apparatus.
Mounting of the specimen included opening TestBuilder and setting the
parameters for the tension test. Setting the parameters of the ZPM consisted of
inputting the necessary information into the universal testing machine, such as
velocity of the ZPM actuator, rate of force and what data needed to be collected.
Once the parameters in TestBuilder were set the experimental procedure was
carried out by the Lab Technician.
From there, the Aluminum specimen was put onto the supports in the
machine. From there the ZPM was started, and a load was applied to the
specimen. Data from this tensile loading was recorded.
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Ansys procedure
To begin the ansys procedure, first the element was defined using the
BEAM3 element. Then the material properties were given values of EX=2e5 and
PRXY=0.3. After that the geometric properties were defined with a height and
width of 10. Keypoints were then defined along with the lines and meshing. The
solution was then found by applying the appropriate constraints and applying
loads.
Specimen Specifications
The specimens dimensions are as follows:
Length - 290mm
Diameter - 6.0mm
Material - Aluminum
Image 2 shows a picture of the tested specimen
.
Image 2: Test specimen
Results
Data collected is as follows:
After we collected the data (shown above), we can then draw comparisons for
the calculated value for the maximum critical load that is applied to the specimen
before it is permanently damaged.
In this experiment, we employ the equation listed below in order to
calculate the theoretical value of the load at which the specimen is permanently
damaged.
P=(π2E)/L
e
2
Here,
P is our critical load
E is the modulus of elasticity of the material being tested
‘Le’ is the effective length of the specimen.
For this experiment, our effective length is the same as our specimen length due
to the fact that we used a dual-pinned end setup for the testing.
Ansys Results
‘Ansys Results’ shows
the final result from the Ansys procedure described
above. This is the computational displacement that the member should
encounter based on the prescribed notions.
Ansys Results
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Validation and Discussion
Given the data shown above in our table above, we are able to calculate
the value for our modulus of elasticity (E) from the maximum displacement value
given - shown below in our appendix section. With our modulus of elasticity value
obtained, we can calculate the maximum stress we obtained given the initial
length of the specimen and the change in it.
For our value of the maximum stress (shown in our appendix section), we
had a value of 409.26 N of force applied to the specimen, which in turn gave us a
value of 93.7 MPa for our maximum stress value. Unfortunately, in our
experiment, we were unable to apply enough force to actually displace the
specimen enough that it would be permanently displaced. This was due to the
fact that the machine we were using was unable to apply the force necessary.
Conclusion
Although the alternate test stand was incapable of producing the forces
necessary to cause the specimen to fail completely, we were able to achieve a
predicted outcome up to the upper limits of the alternate ZPM. In the future a
better demonstration may be achieved by using a ZPM that is capable of causing
the specimen to fail. Despite challenges in the experiment, our understanding of
the material properties involved was reinforced.
Appendix
REFERENCES
[1]
“Column Buckling and Why It's Important to Know About.”
Tribby3d
, 10 Aug. 2022,
https://tribby3d.com/blog/column-
buckling/#:~:text=Column%20buckling%20is%20a%20phenomenon,column%20can%2
0resist%20before%20buckling.
[2]
Khandaker, M. (2021).
Laboratory Manual for Strength of Materials Lab
.
Department of Engineering and Physics (UCO).
[3]
Hibbeler, R. C.
Mechanics of Materials
. Pearson, 2022.
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