Selection Criteria Properties Availability Cost Manufacturability Most designers select materials considering Properties Availability Cost Manufacturability

Properties Mechanical Yield strength (ductile) / Ultimate strength (brittle) Fatigue (endurance limit) Stiffness or rigidity (modulus of elasticity) Hardness (Rockwell, Brinell) Impact strength (fracture toughness) Toughness (sharpy test) Ductility (% reduction is area) Hardenability Creep (elevated temperature properties) High/Low temperature properties Wear characteristics

Properties Physical Chemical Toxicity Resistance to radiation Density Electrical properties Thermal properties (conductivity) Magnetic Melting point Thermal expansion Flamability Optical Chemical Corrosion resistance Oxidation resistance Toxicity Resistance to radiation Resistance to elements Dimensional Dimensional stability Surface finish

Availability Important questions: Is the supply plenty, stable, and predictable Is the material available in the desired form? Gage 10 sheets of 304L stainless steel? Do we have to order 100,000 lbs? Is the material available from company-certified vendors and multiple suppliers?

COST The primary factor in material selection in industry Comparative cost of engineering metals per pound Hook design: Tungsten In school: Properties important / cost no issue In industry: Cost also very important

COST Cost per volume may be a better choice. The following table is $/in3

Other Cost Factors What is the cost of material in relation to the production cost or selling price? Is it an orbiting satellite or a hammer? What is the production volume? A one of a kind design, or Garden Weasel? What are the primary and secondary manufacturing processes?

Manufacturability Primary processes Forming Rolling (hot or cold) + forging + upsetting + bending + drawing Machining Turning + milling + drilling + broaching + sawing Casting Sand casting, investment casting, die casting Welding Laser cutting + water jet cutting PM technology

Manufacturability Secondary processes Forming Finish forming Machining Turning + milling + reaming + grinding + lapping + honing Heat treatment Deburring Plating + coating

Manufacturing Machinability Weldability Formability, bendability Cutting forces, chip formation, hardness, work hardening Weldability Heat affected zone, brittleness, distortion, oxidation, cracking Methods, setups Formability, bendability Ductility, strength, hardness Castability Melting point, runniness, minimum thickness Heat treatment Hardenability

Designer’s Choices Know about the properties of a few carbon steels Know about the properties of a few cast irons Class 20, Class 60, Ductile 60-45-18 Know about the properties of a few alloy steel 4140, 4340, 9310 Know about the properties of a few tool steels 01, A2, D2, S1, H13, M2 Know about the properties of a few stainless steels 304, 304, 316,420,440C, 17-4 PH

Designer’s Repertoire Know about the properties of a few Aluminum alloys: 3003, 5052, 6061, 7075 Know about the properties of a few nickel alloys: Monel, Inconel Know about the properties of a few copper alloys: C36000 yellow brass, C52100 phosphor bronze Know about the properties of a few titanium alloys Know about the properties of a few Magnesium alloys

Designer’s Repertoire Know about the properties of a few ceramics Aluminum oxides Silicon nitride / Silicon carbide Cemented carbides Carbon products Ceramic coatings (Chromium oxide, Tungsten carbide) Know about the properties of a few plastics: Polyethylene / Polyimides / Polyamides Polycarbonate PVC /ABS Nylons Elastomers

Example Bolt tester material selection Criteria for selection: High strength to weight ratio High strength in tensile (bending) condition Some Toughness (ability to absorb impact load) Rigidity Manufacturability (and possibly weldability) Availability in plate form Cost

Choices a-ksi b c d e f g Rating 1040HR 42 25% 30 $ 4 1030CD 64 -   a-ksi b c d e f g Rating 1040HR 42 25% 30 G $ 4 1030CD 64 - 1095HR 66 9% 5 4140 ann 61 26% $$ Class60 60 Poor 15 E A47 32 10% 3 80-55-06 52 11% 4340 ann 68 22% 4340 QT 215 12% P ? $$$ 9 304 ann 40 60% 27 $$$$ 538 (C) 290 $$$$$ 8 7075 TC 73 10.4 G (ann)

Selection My choices  4340 or 4140 in anneal condition with subsequent HT ASTM 538 Grade C or any other available grade