Identifying Elements of Materials

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Nov 29, 2013 (3 years and 11 months ago)

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Module E: Presentation

Identifying Elements of Materials

and Structural Design


Department of Defense Education Activity

Robotics Engineering


CTE502

Career and Technical Education

Robotics Engineering (CTE502)


DoDEA Career and Technical Education

Module A: Presentation


Setting Expectations for Student Success

Revised 14 July, 2012



History of Architecture


Branches of Engineering



Architectural Engineering
-

focus on safety, cost, and
construction methods of designing buildings


Civil Engineering
-

build bridges, dams, buildings, roads and other
large structures often, incorporating the use of concrete.


Industrial engineering
focuses on organizing the people, information,
energy, materials, and machines involved in the production process.


Manufacturing engineering
is a branch that deals with the design,
plan, develop, improve, and manage the machinery, processes, and
systems that produce these products.


Material engineers
study the properties of existing materials, find
new ways to work with them and develop new materials.


Metallurgical and materials engineers
extract, process, refine,
combine, and manufacture natural substances to create new
materials that are stronger and resist corrosion.


Plastics engineers
study the properties of polymer materials. They
also design machines used to manipulate and shape plastics.

Objects

When initiating a design project of any kind, two
components to focus on are:


Structure and Function


It is essential to take the shape and purpose of the
item into consideration when choosing materials.
These will lead to identifying the constraints of
the design project.

Structures


Bridges
: Truss, Arch, Suspension



Domes
: masonry, cast
-
iron, Geodesic



Skyscrapers
: towers, columns, trusses



Dams
: Arch, Buttress, Embankment,
Gravity



Tunnels
: Soft
-
ground, Rock, Underwater

Materials


Non
-
metallic


Properties


Brittle


Do not conduct electricity


Examples


Wood


Ceramics


Properties

»
Brittle

»
Hard

»
Strong in
compression,

»
Weak in shearing
and tension


Plastics


Properties

»
Flexible

»
Lightweight

»
Strong in
compression and
tension

»
Long lasting




Metallic


Properties


Conduct electricity


Malleable


Ductile


Examples


Mined


Copper


Aluminium


Iron


Alloys


Mixtures of
metals/nonmetals

»
Bronze = Cu +
Sn

»
Brass= Zn + Cu

»
Steel= Fe + C



Plastics


Thermosetting plastics


Retain their shapes


Cannot return to their
original form once cooled
and hardened


Hard and durable.


Uses: auto parts, aircraft
parts and tires.


Examples include
polyurethanes,
polyesters, epoxy
resins


and
phenolic

resins



Thermoplastic


Can soften upon heating


Return to their original
form.


Easily molded


Uses: extruded into films,
fibers and packaging.


Examples include
polyethylene (PE)
-
,
polypropylene (PP) and
polyvinyl chloride (PVC).


Common Polymers


Polyethylene
terephthalate

(PET or PETE)


A thermoplastic that can be pulled into fibers (like Dacron) and drawn into films

(l
ike
Mylar). It's the main plastic in food storage bags.


Polystyrene (Styrofoam):



Can form a hard impact
-
resistant plastic for furniture, cabinets (for computer monitors and TVs),
glasses and utensils. When polystyrene is heated and air blown through the mixture, it forms
Styrofoam
.
Styrofoam is lightweight, moldable and an excellent insulator.


Polyvinyl Chloride (PVC):



A thermoplastic that when made, it's brittle, so manufacturers add a plasticizer liquid to make it soft and
moldable. PVC is commonly used for pipes and plumbing because it's durable, can't be corroded and is cheaper
than metal pipes. Over long periods of time, however, the plasticizer may leach out of it, rendering it brittle and
breakable.


Polytetrafluoroethylene

(Teflon):



Teflon was made in 1938 by DuPont. The polymer is stable, heat
-
resistant, strong, resistant to many chemicals and
has a nearly frictionless surface. Teflon is used in plumbing tape, cookware, waterproof coatings, and bearings.


Polyvinylidine

Chloride (Saran):



Dow makes Saran resins, that can be drawn into films and wraps that are impermeable to food odors. Saran wrap
is a popular plastic for packaging foods.


Polyethylene,
LDPE

and
HDPE
:



The most common polymer in plastics is polyethylene, It was first used to insulate electrical wires, but today it's
used in films, wraps, bottles, disposable gloves and garbage bags (
LDPE
).
HDPE

was first introduced in the hula
hoop, but today it's mostly used in containers.


Polypropylene (PP):



Used in

car trim, battery cases, bottles, tubes, filaments and bags.

www.science/howstuffworks.com/plastic.html


How Plastics are Shaped


Extrusion:


Pellets are heated and mechanically mixed, forced through a small
opening and cooled with air or water.


This method is used to make plastic films.



Injection molding:


Pellets are heated and mechanically mixed and then forced under high pressure into
a cooled mold.


This process is used for containers like butter and yogurt tubs.



Blow molding:


This technique is used in conjunction with extrusion or injection molding. Pellets are
heated and compressed into a liquid tube, like toothpaste. The resin goes into the
chilled mold, and compressed air gets blown into the resin tube. The air expands the
resin against the walls of the mold.


This process is used to make plastic bottles.



Rotational molding:


Pellets are heated and cooled in a mold that can be rotated in three dimensions. The
rotation evenly distributes the plastic along the walls of the mold.


This technique is used to make large, hollow plastic items (toys, furniture, sporting
equipment, septic tanks, garbage cans and kayaks).


www.science/howstuffworks.com/plastic.html


Forces


Tension


Stretches materials apart



Compression


Squeezes materials together



Torsion


Twists materials


Shapes


What happens when you apply a force to each of
these shapes?







Activity: Using only one file folder, balance as
many textbooks as possible. Books must be at
least 10 cm off the table. What shape supports
the most books? Why?


Trusses


What makes them so strong?


Fasteners


Nuts and Bolts


Screws


Nails


Rivets


Glue