1. Objectives of this Chapter
To identify technical objects
To learn the characteristic properties of materials
To choose materials appropriate for the construction of particular technical objects
To learn the properties and types of links between materials
To choose appropriate linking types when constructing technical objects.
To learn about complex mechanical functions
To choose appropriate motion transmission systems for certain technical objects.

2. Technical Objects and Materials
Chapter 12.1
Technical Objects and Materials

3. They meet wants and needs ie. They are useful!
Technical Objects
A technical object is an object conceived and manufactured by humans to meet one or more needs or wants
Name some technical objects you use every day.
They are made by people
They meet wants and needs ie. They are useful!

4. Technical Objects Not Technical Objects (natural objects)
Debate points:
Are cultural and artistic objects technical?
Would cloned animals be natural or technical objects? What about cloned people?

5. Technical Objects are Made from Materials
There are three categories of materials used to make technical objects:
1. RAW materials.
2. Processed MATERIALS.
3. EQUIPMENT.
These terms will be defined in the next three slides.

6. Raw Materials
Raw Materials are natural substances that must be transformed (or processed) before being used to manufacture things.
Examples:
Trees (must be processed or cut into boards before we can use their wood to build with).
Iron ore (must be processed or smelted to make steel before we can build things with it).

7. Materials (AKA. processed or transformed materials)
Materials are substances that have been transformed so that we can use them to make things.
Examples:
Steel made from iron, carbon and other metals
Wood made from trees
Glass made from sand, SiO2
Paper made from trees, cellulose
Etc…

8. Equipment
Equipment is the instruments and tools that we use to produce an object.
Examples:
Hammers
Saws
Screwdrivers
Lathes
Drills
Etc.
Even a whole factory full of equipment may be needed to produce some technical objects.

9. Constraints
A mechanical constraint describes the type of stress produced within an object when it is subjected to external forces.
The five main types of constraint forces:
Compression (squeezing)
Tension (pulling)
Torsion (twisting)
Bending (deflection)
Shearing (cutting)

10. Deformations
A deformation is what happens to a material when a constraint is too great for the material to resist:
Three types of Deformation:
Elastic Deformation: a temporary deformation. The material returns to its original shape
Plastic Deformation: a permanent shape change. The material remains deformed
Fracture: The material breaks or is cut.

11. Mechanical Properties
Mechanical properties determine how a material will react to constraints.
Examples of mechanical properties:
Hardness resists penetration, difficult to make holes in.
Elasticity regains its original shape, springy.
Resilience resists impacts without breaking, strong.
Ductility stretches without breaking, like wire.
Malleability dents or bends without breaking
Tensile Strength resists tension without breaking, like a cable.

12. Chapter 12.2
Wood as a Material

13. Wood Wood is a material that comes from cutting and processing trees.
There are four reasons why wood is such a commonly used material:
Wood is easily worked
Wood is easy to assemble
Wood is a good thermal insulator
Wood does not conduct electricity.

14. Types of Wood: Hardwoods come from deciduous trees.
Examples of hardwood:
Maple, birch, oak
Hardwoods are used where strength and durability are important:
Flooring, furniture, cabinetry, support columns
Softwoods come from coniferous trees.
Examples of softwood:
Pine, spruce, cedar
Softwoods are used for their flexibility and lower cost.
Decks, walls, framing houses

15. Modified Wood
Modified wood is treated wood or material made of wood mixed with other substances.
Examples of modified wood:
Treated wood treated with heat or chemicals to slow/avoid rotting.
Laminated wood short pieces of wood glued together.
Plywood sheets of wood glued together
Particle board wood chips bonded together
Fibreboard wood fibres bonded together

16. Pressure Treated Wood

17. Plywood
Stacked, close-up and used in construction of a sub-floor

18. Particle Board
Close up
Used in construction

19. Fibreboard Used in less expensive parts of furniture
(black painted part)

20. Assignments on Wood Read Textbook pages 373 to 377
Know:
Definition of wood
Mechanical properties of wood
Advantages of wood
Types of wood and the differences between them.
Do Workbook pages 199 to 202

21. Metals and Alloys as Materials
Chapter 12.3
Metals and Alloys as Materials

22. Metals
A metal is an element extracted from an ore. All metals have the following five properties, to varying extents:
Shiny lustre polished metals are shiny.
Good conductor of heat metals carry heat well.
Good conductor of electricity metals conduct electricity.
Malleable metals may be bent or hammered into sheets without breaking.
Ductile metals stretch without breaking.
(that’s how we make wire!)

23. Some Common Metals Iron Copper Aluminum Zinc Magnesium Nickel Chrome*
IRON (Fe) most common, rusts
Silvery-gray metal.
Magnetic properties
Affordable.
Good ductility.
Good malleability
Good resilience
Main uses:
Automobiles, buildings
Tools, cables, nails.
Iron
Copper
Aluminum
Zinc
Magnesium
Nickel
Chrome*
Tin
COPPER (Cu)
pinkish brown metal
excellent ductility
good malleability
excellent electric conducivity
Main uses:
Electrical wires
Musical instruments
coins
Aluminum(Al)
Silvery white metal
Soft
Very abundant
Fairly good malleability
Good ductility
Excellent electrical conductivity
Light weight
Uses:
Boats, foil, cans, electrical products
Zinc (Zn)
White, slightly bluish tint
Good ductility and malleability
Good corrosion resistance
Used in wires, gutters, and
Surface coatings.
Magnesium (Mg)
A light gray metal, low in density
Burns brightly if ignited
Used in aircraft parts,
lightweight engine parts
Chromium (Cr)
Very shiny metal
Rust resistant
Used to coat other metals
to make them more
resistant and attractive.
Nickel (Ni)
Heavy, strong, shiny metal
Sometimes used in place of iron
Has magnetic properties
Used to be used in coins (5c)
Tin (Sn)
Shiny metal
Used to be used for
tin cans and for making
bronze.
*Chrome is its common name. Its proper name is chromium.

24. Alloys
That’s
“Ferrous” to you
An alloy is the result of mixing a metal with another metal or with a non-metallic substance.
A ferrous alloy has iron as its main ingredient.
Examples of alloys:
Stainless Steel (a ferrous alloy)
Cast iron (a ferrous alloy)
Brass (a non-ferrous alloy)
Bronze (a non-ferrous alloy)
Aluminum alloy (a non-ferrous alloy)

25. Looking ahead! This slide references content we will cover more later.
Alloys are not pure metals, they are homogeneous mixtures.
They don’t have a symbol from the periodic table, like Fe, Cr, Zn or Cu.
They are represented by two or more symbols with dots or hyphens between them (since they are mixed, but not chemically combined)
Examples:
Steel: Fe•C•Cr (iron+carbon+chrome)
Bronze: Cu•Sn (copper+tin)
Brass: Cu•Zn (copper+zinc)

26. Alloys
Cast Iron
Steel
Aluminum alloy
Brass
Bronze

27. Assignments on Metals Read Textbook pages 378-380
Know:
Definition of a metal
Five properties of a metal (from notes)
Eight commonly used true metals
Definition of an alloy
Definition of “ferrous”
Five commonly used alloys
Do Workbook pages 203 to 206

28. Chapter 12.4
Plastics as Materials

29. Plastics
Plastic is a manufactured material made of polymers.(often fossil fuels: petroleum)
Examples of plastic
Polyethylene terepthalate (PETE)
Polyethylene, high or low density (HDPE, LDPE)
Polyvinyl chloride (PVC, vinyl)
Polypropylene (PP)
Polystyrene (PS, Styrofoam)
Polyamide (nylon)
Polymethyl methacrylate (acrylic)