Engineering Materials and their properties.pptx

Properties

1. ENGINEERING MATERIALS AND THEIR PROPERTIES LECTURE 2 Materials Technology Classification of Materials

2. Classification of Materials Materials used in the design and manufacture of products Ceramics Composites Fabrics Metals Plastics Wood

3. 1.1 CLASSIFICATION OF ENGINEERING MATERIALS METALS AND ALLOYS These are inorganic materials composed of one or more metallic elements Characteristics ▪ They usually have a crystalline structure and are good thermal and electrical conductors ▪ Many metals have high strength and high elastic moduli [ changes its shape only slightly under elastic loads (e.g. diamond))] ▪ They maintain their good strength at high and low temperatures.

4. ▪ They also have sufficient ductility, which is important for many engineering applications ▪ They can be strengthened by alloying and heat treatment ▪ They are least resistant to corrosion

5. Classification of Materials (Metals) Metals can be further classified as Ferrous & Non-Ferrous, some examples include; Ferrous Non-Ferrous Steels Aluminium Stainless Steels Copper High Speed Steels Brass Cast Irons Titanium

6. 8 Pure Metals and Alloys Metals that are not mixed with any other materials are known as pure metals. Metals listed in the Periodic Table are pure metals E.g. Iron (Fe), Copper (Cu) and Zinc (Zn) Alloys are mixtures of two or more metals formed together with other elements/materials to create new metals with improved Mechanical Properties and other properties of the base metal. E.g. Brass (Copper and Zinc), Stainless steel (steel and chromium) Alloy = metal A + metal B + … + other elements

7. 9 Ferrous Metals & Non-Ferrous Metals Ferrous metals are metals that contain iron E.g. Steel (iron and carbon) Non-ferrous metals are metals that do not contain iron E.g. Zinc (pure metal), Bronze (Copper and tin) (non-ferrous may contain slight traces of iron) Ferrous Metal = alloy metals that contains iron ( Primary base metal is iron) Non-ferrous Metal = alloy metals that do not contain iron Primary base metal does not contain iron)

8. 10 Classification Metals can be divided into 2 groups Metals Ferrous Metals Non- Ferrous Metals Iron Aluminum Low Carbon Steel Copper Medium Carbon Steel Brass High Carbon Steel Bronze Cast Iron Zinc Stainless Steel Lead Tool Steels Tin Others Others

9. 11 Ferrous Metals - Iron and Steel Pure iron is soft and ductile to be of much practical use. But when carbon is added, useful set of alloys are produced. They are known as carbon steel. The amount of carbon will determine the hardness of the steel. The carbon amount ranges from 0.1% to 4%.

10. 12 Types of Steel Steel Low carbon steel (mild steel) Medium carbon steel High carbon steel (tool steels) Cast iron Alloy Steels Stainless steel High speed steel

11. 13 Low Carbon Steel Also known as mild steel Contain 0.05% -0.32% carbon They are : Tough, ductile and malleable, Easily joined and welded, Poor resistance to corrosion, and Often used as a general purpose material Examples are: Nails, screws, car bodies, Structural Steel used in the construction industry

12. 14 Medium Carbon Steel Contains 0.35% - 0.5% of carbon Offer more strength and hardness BUT less ductile and malleable Examples are: Structural steel, rails and garden tools

13. 15 High Carbon Steel Also known as ‘tool steel’ Contain 0.55%-1.5% carbon Very hard but offers Higher Strength, Less ductile and less malleable Examples are: Hand tools (chisels, punches) Saw blades

14. 16 Cast Iron Contains 2%-4% of carbon Very hard and brittle Strong under compression Suitable for casting [can be poured at a relatively low temperature] Examples are: Engine block, engineer vices, machine parts

15. 17 Cast Iron White: Hard and brittle, good wear resistance Uses: rolling & crunching Equipment Grey: Good compressive & tensile strength, machinability, and vibration-damping ability Uses: machine bases, crankshafts, furnace doors, Engine Blocks

16. 18 Stainless Steel Steel alloyed with chromium (18%), nickel (8%), magnesium (8%) Hard and tough Corrosion resistance Comes in different grades Used in: Sinks, cooking utensils, surgical instruments

17. 19 Stainless Steels Main types: Ferritic chromium: very formable, relatively weak; used in kitchen range hoods, jewelry, decorations, utensils Grades 409, 430, and other 400 Austentitic nickel-chromium: non-magnetic, machinable , weldable , relatively weak; used in architectural products, such as, curtain walls, storefronts, doors & windows, railings; chemical processing, food utensils, kitchen applications.

18. 20 Martensitic chromium: High strength, hardness, resistance to abrasion; used in turbine parts, bearings, knives, e.t.c Maraging (super alloys): High strength, high Temperature alloy used in structural applications, aircraft components and are generally magnetic. Alloys containing around 18% Nickel.

19. 21 High Speed Steel Medium Carbon steel alloyed with Tungsten, chromium, vanadium Very hard Resistant to frictional heat even at high temperature Used in : Machine cutting tools (lathe and milling) Drills, etc

20. CERAMICS AND GLASSES These are inorganic materials consisting of both metallic and non-metallic elements bonded together chemically . CHARACTERISTICS ▪ They can be crystalline(ceramics), non-crystalline(glasses) or a mixture of both (glass-ceramics) ▪ Generally they have high melting points and high chemical stabilities.

21. ▪ They have high hardness, and high temperature strength. ▪ Since they are very brittle they cannot be used as good as metals. ▪ Ceramics are usually poor electrical conductors. ▪ Ceramics have a high strength on compression

22. Classification of Materials (Ceramics) Examples include; Oxides (alumina – insulation and abrasives, zirconia – dies for metal extrusion and abrasives) Carbides (tungsten-carbide tools) Nitrides (cubic boron nitride, 2 nd in hardness to diamond)

23. POLYMERS (PLASTICS) These are organic materials which consist of long molecular chains or networks containing carbon. CHARACTERISTICS ▪ Most polymers are non-crystalline, but some consist of mixtures of both crystalline and non-crystalline regions. ▪ They generally have low densities and low rigidity ▪ Most polymers are poor electrical conductors due to the nature of the atomic bonding

24. ▪ Most polymers are corrosion resistant, but cannot be used at high temperatures

25. Classification of Materials (Polymers-Plastics) Plastics can be further classified as; Thermoplastic Thermoset Elastomers Thermoplastics Thermosets Elastomers Acrylics Epoxy resins Rubbers Nylons Phenolic Silicones PVC Polyesters Polyurethanes Polyethylene

26. COMPOSITES These are materials where two or more of the above materials are brought together on macroscopic level CHARACTERISTICS ▪ Usually they consist of a matrix and a reinforcement. ▪ They are designed to combine the best properties of each of its components.

27. Classification of Materials (Composites) A composite is a combination of two or more chemically distinct materials whose physical characteristics are superior to its constituents acting independently. Because of their high strength/stiffness to weight ratio they are widely used in the; Aerospace industry Offshore structures Boats Sporting goods

28. Classification of Materials (Composites) Examples of composites include; Reinforced Plastics Reinforced plastics are a recent class of composite materials in which the low modulus and temperature limitations of plastic is overcome by reinforcing it with fibres of high modulus . Ceramic-matrix They consist of ceramic fibres embedded in a ceramic matrix , thus forming a ceramic fibre reinforced ceramic (CFRC ) material . Metal-Matrix Metal matrix composites (MMCs) generally consist of lightweight metal alloys of aluminum, magnesium, or titanium, reinforced with ceramic particulate, or fibers Laminates Lamination is the technique of manufacturing a material in multiple layers, so that the composite material achieves improved strength, stability, sound insulation, appearance or other properties from the use of differing materials .

29. Classification of Materials (Fabrics) Fabrics can be further classified as natural and synthetic Natural Synthetic Cotton Nylon Canvas Polyester Canvas deck chair

30. Canvas deck chair

31. Classification of Materials (Smart Materials) A smart material can be described as a material that has a useful response to external influences or stimuli. There are many examples of smart materials in everyday use that are not modern developments they include; Metal springs Light bulbs -self regulate because as the filament temperature increases, their resistance rises Ancient civilisations have long used porous ceramics for self regulating cooling

32. Wine Cooler

33. Classification of Materials (Smart Materials) Other more modern examples of smart materials include; Shape memory polymers and alloys

34. Piezoelectric Materials Sensors, musical cards, motors, actuators, clocks Smart Wire Actuators- linear, angular and rotary Anthromorphic actuation – human like robotic motion

35. Classification of Materials (Smart Materials) Other more modern examples of smart materials include; Polymorph This is a unique polymer that fuses in hot water and can then be moulded to any form. Used to make the moulds for the vacuum formed seat and fuel tank of this motorcycle project

36. Classification of Materials (Smart Materials) Other more modern examples of smart materials include; Thermocolour Sheet This is a self adhesive sheet whose colour changes according to the temperature. Used for thermometers, heat warning patches and novelty advertising of products Inactivated Sheet Finger placed on sheet Sheet changes colour according to temp

37. Classification of Materials (Smart Materials) Other more modern examples of smart materials include; Phosphorescent Sheet This is a sheet that absorbs light energy and re-emits it as white light for up to eight hours. Used extensively for emergency lighting in the event of a power cut

38. Classification of Materials (Smart Materials) Other more modern examples of smart materials include; Lenticular Sheet This sheet is about 1mm thick but gives the illusion that it is nearer to 6mm thick. An object placed on the sheet appears to sink below the surface The camera lens does not capture the effect

39. Classification of Materials (Smart Materials) Other more modern examples of smart materials include; Quantum Tunnelling Composite (QTC) A QTC in its normal state is a perfect insulator When compressed it becomes a perfect conductor If only lightly compressed its conductivity is proportional to the pressure applied

40. Classification of Materials (Wood) Wood can be further categorised as; Hardwood Softwood Manufactured board Hardwood Softwood Manufactured Board Oak Pine Plywood Ash Cedar Blockboard Beech Fir MDF Sycamore Spruce Melamine board