9 Materials Selection 12 points Notes I There may be more th

9: Materials Selection (12 points) Notes: I) There may be more than one appropriate answer, your reasons are important. 2 You can use information at the beginning and end of the exam and other problems as well as the table below ) V-Vickers Hardness; K-Knoop Hardness; S- Shore Hardness (polymer test and scale) Fracture | CTE Strength Toughness x10C (g/em) ie ensi | Density | %EL | TMor | Hardness | Cost Tg CC (2011 s/kg) (GPa) (MPa)(MPa (MPavm) 115 1085 50 (v 45 90-125 40 65 17 23.6 15.9 Cu 7-12 Al 35 2.71 40 660 5 (V) 2.65-2.75 193 1540 138 (K) 129 (V) 249 585 8.00 55 Austenitic V6-20 1040 Steel 207 290-490 500-600 54 7.85 12-30 540 191 (K) 0.90-2.25 176 (V) 29-187 2.33 .. Sic ZrO Window glass High modulus 200 80-130 0.95 00-8005 800-15007-12 4.6 9.6 9.0 1410 1020 (K)5100-14,000 2800 3000 (K) 250 2850 1300 (K) 50-200 600 515 (K) 345 6.0 70 0.75 2.5 0.56-13 0.3 NA (transv 0.4 760 10 0.5 NA Not 120-725 carbon fiber (transverse epoxy matrix6.9 composite (longitu- (transverse longitu 5-95 available 32 longitu- Nylon 6,62 Styrene- 0.002-0.01 144 15-80 185 so (S) 3.20-12.80 2.4-20.7 220 0.94 500 35-99 50 (S) 1.70-5.05 elastomer 131 3600-4100 2-603 2.8 500 Not avai 75-100 (a) If you wanted to make lightweight, non-lubricated ball bearings that would work at 1000°C, what material would you (i) Material: (ii) List at least 2 properties that support your choice and state why each property supports your choice in one bullet

Solution

Answer:

A: Silicon carbide (Sic)

Properties : 1. Density and melting point.

Its less weight because density is 3.3 which is less than most of materials given in table and melting point is 2800°C.

B: austinitic stainless steel:

Properties should have : tensile strength and hardness

It should have high tensile strength without breaking. And corrosion resistance.

C: aluminium (Al)

Properties: density and fracture strength.

It should have less weight i,e. Low density and high fracture strength..