Objectives of this Chapter

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. Chapter 12.1 Technical Objects and Materials

3. Technical Objects • A technical object is an objectconceived 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. 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 (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)