1. (6 points) Which material w you choose for da) a crank shaft of an internal c
ID: 1063521 • Letter: 1
Question
1. (6 points) Which material w you choose for da) a crank shaft of an internal combustion engine, rotor blade and (c a complex housing of cheap DVD player? Give reasons for yo decision. 2. (15 points) State s distinct properties (each) of ceramics, metals and polymers 3. (1 point) What type of material is a house brick? (a) Metals (b) Polymers eramics (d) Composites 4. (2 points) Can you perform tensile test on ceramics? 5. (2 points) what type of non-ferrous would you choose for aerospace alloy applications? Metals (Magres wait ysy. network r 6. points) What is polymerization? The Pnoss by which molecules are 7. (3 points) What is the difference between thermoplastic and thermosettin polymers? ers and composites Ce trave density 9. (3 points) Rank the following materials from lowest to highest Aluminum, titanium and Magnesium 10. points) Polymers are: (a) Liquids at room temperature False (b) Electrical insulators True FalseExplanation / Answer
1.
(a)crank shaft
The steel alloys typically used in high strength crankshafts.
Medium-carbon steel alloys are composed of iron, and contain a small percentage of carbon (0.25% to 0.45%), along with combinations of several alloying elements, the mix of which has been carefully designed in order to produce specific qualities in the target alloy, including hardenability, nitridability, surface and core hardness, ultimate tensile strength, yield strength, fatigue strength, ductility, impact resistance, corrosion resistance, and temper-embrittlement resistance. The alloying elements typically used in these carbon steels are manganese, chromium, molybdenum, nickel, silicon, cobalt, vanadium, and sometimes aluminium and titanium. Each of those elements adds specific properties in a given material. The carbon content is the main determinant of the ultimate strength and hardness to which such an alloy can be heat treated.
(b) A helicoptor rotor blade
Helicopter blades used to be based on an outer skin of duralium which is heavier than modern materials but much easier to repair. Modern blades are based on carbon fibre and composite materials which have a better strength to weight ratio but much more difficult to repair. In fact, in many cases, especially when time is of the essence it is cheaper to completely replace a damaged blade.
(c) a complex housing of a cheap DVD player
A variety of raw materials are used in the construction of DVD players and disks. Glass is used to make the laser and other diodes in the system. The primary components on the circuit board are made from silicon. Aluminum metal is used for the housing as well as a hard plastic. The base material of the disks is plastic. They are additionally coated with a silver colored layer and a thin gold layer. The surface of the disk is further coated with a hard layer of lacquer to protect it from damage.
(2)
ceramics properties:
Most ceramics are hard,wear-resistant,brittle,refractory,thermal insulators,electrical insulators,nonmagnetic,oxidation resistant,prone to thermal shock, andchemically stable.
Metals:Most metals are silvery looking, high density, relatively soft and easily deformed solids with good electrical and thermal conductivity, closely packed structures, low ionisation energies and electronegativities, and are found naturally in combined states.
polymers:
Polymers can be very resistant to chemicals,thermal and electrical insulators.hare very light in weight with significant degrees of strength,low coefficient of friction,good corrosion resistance.Polymers can be processed in various ways. Extrusion produces thin fibers or heavy pipes or films or food bottles. Injection molding can produce very intricate parts or large car body panels. Plastics can be molded into drums or be mixed with solvents to become adhesives or paints. Elastomers and some plastics stretch and are very flexible. Some plastics are stretched in processing to hold their shape, such as soft drink bottles.
4.Tension testing can be conducted on ceramics similar to other material. You are correct that ceramics are elastic, so the stress-strain response will be a positive-slope line from the origin to the maximum stress-strain point. Since ceramics are brittle and difficult to fixture, they normally are bend tested.
8.
Ceramics example:cement,glass,ferrite,porcelain
Polymers: natural polymer: natural rubber,wool,silk
synthetic polymer:resin,neoprene,PVC
composites:carbon fibers,silicon carbide
9.
Magnesium density=1.74 g/cm3
Aluminium density= 2.7 g/cm3
titanium density =4.506 g/cm3
17.
Plastic bag- polyethylene polymer
water pipes= polyvinyl chloride
outer layer of electic wire=polyethylene
clothing:cellulose,wool,silk,polyacrylonitrile,nylone
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