New work
A)
"Transfer It" Please respond to the following:
· Using 140 characters or less (the length of a Tweet), summarize the importance of this class to someone unfamiliar with the concepts.
· Discuss ways you can apply what you learned in this course to your current or future position.
Note: this is the class of INTRODUCTION OF COMPUTER INFO SYSTEM
ABSTRACT
The report describe the results obtained from a tensile test. This was in determination of the ultimate tensile strength of both metals and polymeric materials. It is common knowledge that materials have certain unique properties but assigning the exact values to them requires a well outlined laboratory procedure. The materials under testing were; steel, aluminum, high density polyethylene, and low density polyethylene. The results obtained were analyzed and presented in graphical form.
INTRODUCTION
The Ultimate Tensile strength of a material is the maximum amount of stress that a given material can tolerate when pulling forces are applied at both ends, without failing. Ultimate Tensile strength is differentiated from compressive strength in that the former is acted upon by forces that pull a material outwards on both sides while the latter is acted upon by forces that push a material inwards. (David, 2008) Tensile strength is determined by using a cylindrical sample of known length and cross sectional area and subjecting it to tensile forces in a tensile machine. Most commonly used tensile machines include: lab master z-direction tensile tester and universal tester. (David, 2008) When the tests are carried out, the stress-strain relationships is easily determined hence making it easy to deduce the ultimate tensile strength of the material specimen and its young’s modulus.
When designing for rigid structures, the properties of various construction materials need to be determined. (David, 2008)The reason being materials are subject to external forces when used in construction of structures. Different materials have different properties due to differences in their molecular structure. This fact is evident in the case of metals and polymeric samples which exhibit different physical and chemical properties due to variances in molecular structure and in extension atomic composition. This makes them react differently to when subjected to external forces. Metal are generally stronger than polymers hence used in area which experience heavy loading in a structure. In order for one to find the most suitable material for a particular project, material property needs to be known, with the most natural property being tensile strength.
Steel and aluminum are the most commonly used metals in construction projects. They have both high electrical and thermal conductivity, relatively high densities, high melting points, and both high ultimate and yield strength. (Gordon, 1976)Steel is mostly used together with concrete to form rigid structure such as buildings and dams. Aluminum is mostly us ...
New workA)Transfer It Please respond to the following· U.docx
1. New work
A)
"Transfer It" Please respond to the following:
· Using 140 characters or less (the length of a Tweet),
summarize the importance of this class to someone unfamiliar
with the concepts.
· Discuss ways you can apply what you learned in this course to
your current or future position.
Note: this is the class of INTRODUCTION OF COMPUTER
INFO SYSTEM
ABSTRACT
The report describe the results obtained from a tensile test. This
was in determination of the ultimate tensile strength of both
metals and polymeric materials. It is common knowledge that
materials have certain unique properties but assigning the exact
values to them requires a well outlined laboratory procedure.
The materials under testing were; steel, aluminum, high density
polyethylene, and low density polyethylene. The results
obtained were analyzed and presented in graphical form.
INTRODUCTION
The Ultimate Tensile strength of a material is the maximum
amount of stress that a given material can tolerate when pulling
forces are applied at both ends, without failing. Ultimate
Tensile strength is differentiated from compressive strength in
that the former is acted upon by forces that pull a material
outwards on both sides while the latter is acted upon by forces
that push a material inwards. (David, 2008) Tensile strength is
2. determined by using a cylindrical sample of known length and
cross sectional area and subjecting it to tensile forces in a
tensile machine. Most commonly used tensile machines include:
lab master z-direction tensile tester and universal tester. (David,
2008) When the tests are carried out, the stress-strain
relationships is easily determined hence making it easy to
deduce the ultimate tensile strength of the material specimen
and its young’s modulus.
When designing for rigid structures, the properties of various
construction materials need to be determined. (David, 2008)The
reason being materials are subject to external forces when used
in construction of structures. Different materials have different
properties due to differences in their molecular structure. This
fact is evident in the case of metals and polymeric samples
which exhibit different physical and chemical properties due to
variances in molecular structure and in extension atomic
composition. This makes them react differently to when
subjected to external forces. Metal are generally stronger than
polymers hence used in area which experience heavy loading in
a structure. In order for one to find the most suitable material
for a particular project, material property needs to be known,
with the most natural property being tensile strength.
Steel and aluminum are the most commonly used metals in
construction projects. They have both high electrical and
thermal conductivity, relatively high densities, high melting
points, and both high ultimate and yield strength. (Gordon,
1976)Steel is mostly used together with concrete to form rigid
structure such as buildings and dams. Aluminum is mostly used
in construction of planes, electric cables and engine blocks.
Polymeric materials have both low electrical and thermal
conductivity, relatively low densities, low melting points and
both low ultimate and yield strength. Low density polyethylene
is used in making of playground slides, six pack rings, and
plastic wraps. High density polyethylene is used in making of
fuel tanks for vehicles, 3-D printer filaments, and swimming
3. pool installations. (David, 2008)
THEORETICAL
After carrying out tensile tests, the data obtained needs to be
analyzed. This is achieved by use of engineering formulae
related to stress and strain. They include:
Formulae
Where;
Where;
Where;
EXPERIMENTAL
Equipment
1. Vernier calipers.
2. Tensile testing machine.
3. Computer (installed with DOS).
PROCEDURE
1. Visual inspection of the sample was done to identify possible
flaws.
2. The width, thickness, and length of the metal and polymeric
4. samples were measured.
3. The machine’s computer was calibrated with the results
obtained in procedure two and prepared to receive data and
present it graphical form.
4. Steel specimen was placed in the tensile machine and
clamped in place.
5. The machine was activated and force and elongation readings
displayed were noted and recorded.
6. Procedure two, three, and four was repeated for aluminum,
low density polyethylene, and high density polyethylene
specimens.
7. The data was analyzed by and presented in graphical form.
RESULTS
Specimens
Width (inches)
Thickness (inches)
Gage length
After fracture load (lbs)
Percentage elongation
Aluminum
0.49
0.12
3.05
3675
45.66
Steel
0.48
0.12
1.82
4258
18.76
High density polyethylene
0.72
0.12
3.82
5. 409
18.25
Low density polyethylene
0.74
0.12
3.07
140
197.91
DISCUSSION
Materials behave differently when acted upon by external
forces. Some deform more than others while some fracture
almost immediately. This behavior is governed by the properties
each material possesses. In order to determine these properties,
a series of tests is carried out each material. An example of such
a test is the tensile test. Specimens of known dimensions are
tested and in this case their thickness were constant at 0.12
inches. The materials whose properties were to be determined
were steel, aluminum, high and low density polyethylene. The
first two are known as metals while the last two are known as
polymeric.
When steel was subjected to the test, the ultimate tensile stress
was found to be 23 ksi while that of Aluminum was found to be
4.6 ksi. Though both of them are metals, they possess different
tensile strength due to variation in the constitution and atomic
structures. However both experience are reasonable length of
linear relationship in stress-strain graphs. When high density
polyethylene was subjected to test, its ultimate tensile strength
was found to 0.896 ksi while that of low density polyethylene
was found to be 0.494 ksi. The difference is brought about by
the difference in intermolecular forces. High density
polyethylene has a higher tensile strength as compare to low
density polyethylene, because the former has strong
intermolecular forces due to little branching while the latter has
weak intermolecular forces.
During testing, it is found that both the metals and polymeric
6. materials undergo necking beyond a certain elongation. The
necking is caused by localized and increased flow in the length
of the sample when the maximum true stress is reached. It is at
a point when the localized flow cannot be reimbursed by further
strain hardening. The polymeric materials further experience
drawing. It is phenomenon where the neck spans the full length
of the specimen. The cross section areas of the specimens affect
the ultimate tensile strength of materials but their lengths do
not. It is due to increase in interplanar bond between adjacent
cross sections. These bonds are stronger in specimens with large
cross section areas. This is the reason for keeping the thickness
constant.
However, the values obtained in this experiment were
significantly smaller as compare to the standard values. This
could be as a result of human error during the experiment.
7. CONCLUSION
In conclusion, it is found that metals have higher ultimate
strengths as compared to polymeric materials. The order of
strength in descending order is steel, aluminum, high density
polyethylene, and low density polyethylene respectively. The
shear graph for the materials turned out as expected. They
obeyed hook’s law at first and when the yield strength was
reached, they formed a curve to signify permanent deformation.
The necking of the metals occurred as anticipated with the outer
region showing signs of shear failure and the middle region
showing signs of tensile failure.
REFERENCES
Anderson, T. (1991). Fracture Mechanics: Fundamentals and
Applications. Boca Raton: CRC Press.
David, R. (2008). Mechanical Properties of Materials. New
York: CRC press.
Gordon, J. (1976). The New Science of Strong Materials.
Princeton University Press.
Hertzberg, R. (1976). Deformation and Fracture Mechanics of
Engineering Materials. New York: Wiley Publishers.
Knott, J. (1973). Fundamentals of Fracture Mechanics. New
York: Halsted Press.
T2836.xls
Curve_TableTESTNUMPOINTNUMTIMEPOSITFORCEEXTCH
5CH6CH7CH8283610.439019.39436340330283620.5360.00005
21.54318618770.0014492701283630.6350.000338.03575515750
.0086956499283640.7350.0006567.86193847660.018840579328
3650.8370.00199.56145477290.0289855003283660.9380.00132
5129.97535705570.0384057909283671.0330.00165159.9852142
3340.0478260815283681.1380.0020000001186.23007202150.05