Design Challenge II: Forces & Materials
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Prepared by : Fadhel Ali
201102569
Prepared
for: Danielle
McArthur, English for Engineering 2
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Table
of content
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Page:
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Cover Sheet
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1
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Table of content
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2
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Introduction
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3
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The Original Mechanism
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3
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The Real-life Application
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7
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The Forces Affecting the Mechanism
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7
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Necessary Material
Properties for this Mechanism
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8
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New Material Research Findings
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8
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Recommendations for use
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9
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Conclusion
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9
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References
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10
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11
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Introduction
Mechanisms and machines are vulnerable to be affected by
various forces, such as friction, air resistance, gravitational, attractive,
repulsive and counter forces. Forces’ effects can be either positive or
negative depending on which situation they are exerted in. For example, the
force of friction is not desirable in a gears mechanism but it is useful and
necessary in any break system.
It is important to select suitable materials in order to make
a good mechanism. Appropriate materials can be determined by defining the
functions of the mechanism and understanding the properties of materials. For
instance, if a part of a mechanism is movable, it is better to chose flexible
and malleable materials, such as aluminum and plastic.
At present, new materials play an effective role in
developing technologies. These materials give scientists more flexibility and
choices to do their research that assists in the development of
technology.
This report will focus on the modification of the mechanism
of the gripping device that was designed in a previous design challenge. Its
function was to hold and transfer objects from point to another. One of
real-life applications that were visualized is an automatic washing-machine
that can put in and pick up clothes from place to another.
The first section of the report will describe the original
mechanism. In the next section, a detailed description of the real-life
application will be provided. Then, the properties of a new material will be
explained. Finally, how this material can be used in the real-life mechanism
will be discussed.
The Original Mechanism
In the previous design challenge project, a gripping machine
was made by using simple equipment and combining simple machines together. The
device consisted of three main parts: a gripper, a horizontal motion system and
a vertical motion system. In these three parts, three different simple machines
were used.
In the first moving part (the gripper), a lever simple
machine was used in order to open and close it. By putting an effort on the
handle of the gripper, the gripper arm moved in the opposite direction of press
which made it open. On the other hand, by removing the effort from the handles,
it locked. See figure 1.
Figure 1. How to lock and release the load.
Figure 2. The horizontal
motion arm.
Figure
3. The crank mechanism
Finally, in order to move the load up and down, the pulley
system was used. The two ends of the rope of the pulley were tied to two
sliding pieces and by rotating the pulley, the gripper moved vertically. See
figure 4.
Figure 4. The vertical motion mechanism
(pulley system).
The Real-life Application
The imagined real-life application is two arms that would be
attached to a washing machine in order to assist in the process of picking up
and putting clothes from place to the washing machine or the opposite. The same
technique of horizontal motion of the previous mechanism would be used in the
visualized device but with using electrical motor. In addition, a pneumatic
system would be used rather than the pulley system in the vertical motion mechanism.
Furthermore, all techniques would be controlled by using a programmable logic
controller (PLC).
It would be a useful application because the process of the washing
machine would be in a continuous sequence. It would be also helpful for hotels and
laundries because it would assist to minimize the pays of workers due to the
fact that it would not be needed for workers to fill the washing machine with clothes
or to re-operate it after each wash. Additionally, to make the device work properly
it is important to determine the real life of the device. However, the scale of
the arms would depend on the size of the washing machine.
The
Forces Affecting the Mechanism
One of forces that would affect the mechanism is a centrifugal force.
When an object is rotating, there is a centripetal force that attracts the
object to the center of rotation. Newton’s third law of motion says that every
action has an equal reaction toward the opposite direction. As a result,
centrifugal force occurs as a reaction of the centripetal force and attempt to
make the object repel from the center of rotation. ("Centripetal force and
centrifugal force," 2013).
While the
washing machine is running, the inside part of it is rotating. Consequently, a
centrifugal force would appear as a reaction to the centripetal force. As a
result of the centrifugal force, the washing machine would vibrate.
Necessary
Material Properties for this Mechanism
In this
mechanism there would be fixed and moving parts. For the fixed part -which
would be the slider path- it would be better to build it from a tough material
because it would carry the two arms. In this case it is also necessary to use a
malleable material to adjust the slider (the path) to make it fit with the
sliding piece. Malleability is the amount of deformation that materials can be resisted
without braking. (Bell, 2012)
Furthermore, for moving parts- the gripper and sliding
pieces- it would be preferred to use corrosion resistant and light materials in
order to make the motion more easy, flexible and smooth.
New
Material Research Findings
Carbon fiber is a new material that belongs
to the polymers family and it consists of fibers and polymers of graphite. In
1800’s carbon fiber was discovered by Thomas Edison but it had a low tensile
strength and a very good heat resistant. Carbon fibers spread out when a high
tensile strength was discovered on 1950’s by Rayon. ("The history of
carbon fiber," n.d. and "High performance carbon," 2003)
Carbon fiber
has many properties that make it popular in the engineering field, such as high
stiffness, high tensile strength, light weight, high chemical resistance, high
temperature tolerance and low thermal expansion. ("Carbon (fiber),"
2013 ). Its light weight and stiffness would be useful in building the
mechanism.
Its stiffness is gained from its chemical structure. “It is
made of carbon crystals aligned in the long axis. These honeycomb shaped
crystals organize themselves in long flattened ribbons. This crystal alignment
makes the fiber strong”. ("Carbon
fiber characteristics, n.d." )
Recommendations
for Use
Carbon fiber would be a suitable
material to use in making the mechanism. Its properties could be useful for the
mechanisms especially its light weight and stiffness. The mechanism would gain
the advantages of transportation possibility -that would allow to the user to
separate and attach the two arms easily- and high strength.
Carbon fiber could be used in making the slider path- which would
carry the two arms- because it would be strong enough to lift the two arms due
to its high stiffness. Furthermore, carbon fiber would be also appropriate for building
the two arms of the mechanism due to its light weight which make them transport
easily.
Conclusion
To conclude, a real-life application for the previous
challenge project was visualized. In addition, this report described the
imagined vision of the application by explaining the uses of the mechanism, the
forces that could affect it and the properties of the materials that could be
used for it.
In the second part of findings, the report focused on carbon
fiber’s properties, history and family. Furthermore, an explanation of how
carbon fiber could be used in the mechanism was provided. Nowadays the engineering
field is reflecting the significant importance of innovation by providing new
ideas in different ways in order to create an easy and simple life. Finally, to
cover people’s needs and to have a comfortable living, more and more new
materials are discovered.
Appendix A
Figure 5. The original mechanism
References
Bell, T. (2012). Malleability.
Retrieved from http://metals.about.com/od/metallurgy/a/Malleability.htm
Carbon fiber
characteristics. (n.d.). Retrieved from http://www.christinedemerchant.com/carboncharacteristics.html
Carbon (fiber). (2013 , May 30 ). Retrieved from
http://en.wikipedia.org/wiki/Carbon_(fiber)
Centripetal force and centrifugal force. (2013). Retrieved
from http://www.infoplease.com
/encyclopedia/science/centripetal-force-centrifugal-force.html
High performance carbon fibers. (2003, September 17). Retrieved from http://portal.acs.org
/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_SUPERARTICLE&node_id=717&use_sec=false&sec_url_var=region1&__uuid=3bcbdb4a-7a52-4a8a-8ed1-c2e0960d1ca1
The history of
carbon fiber. (n.d.). Retrieved from
http://www.hj3.com/company/history-of-carbon-fiber/
(2012, July 18).
crank-animation [Web Photo]. Retrieved from http://www.google.com.bh/ url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&docid=nFpwlzKBz2oQJM&tbnid=-arNFPA4NMPxRM:&ved=&url=http://www.explainthatstuff.com/cranks-and-cams.html&ei=KWPDUbuHOcuWhQed54Aw&psig=AFQjCNE2ECMbGNV9PNVkilLCSNxHDHsTrg&ust=1371845802414021
