Module E: Presentation

Identifying Elements of Materials

and Structural DesignDepartment of Defense Education Activity

Robotics Engineering – CTE502Career and Technical Education

Robotics Engineering (CTE502) – DoDEA Career and Technical EducationModule A: Presentation – Setting Expectations for Student SuccessRevised 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 (like 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