mse22 - CHAPTER 22: MATERIALS SELECTION AND DESIGN...

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1 Chapter 23 - 1 ISSUES TO ADDRESS. .. • Price and availability of materials. • How do we select materials based on optimal performance? • Applications: -- shafts under torsion -- bars under tension -- plates under bending -- materials for a magnetic coil. CHAPTER 22: MATERIALS SELECTION AND DESIGN CONSIDERATIONS Chapter 23 - 2 • Current Prices on the web: e.g., http://www.metalprices.com -- Short term trends: fluctuations due to supply/demand. -- Long term trend: prices will increase as rich deposits are depleted. • Materials require energy to process them: -- Energy to produce materials (GJ/ton) Al PET Cu steel glass paper 237 (17) 103 (13) 97 (20) 20 13 9 -- Cost of energy used in processing materials ($/MBtu) elect resistance propane oil natural gas 25 17 13 11 Energy using recycled material indicated in green. PRICE AND AVAILABILITY
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2 Chapter 23 - 3 RELATIVE COST, c , OF MATERIALS • Reference material: -- Rolled A36 plain carbon steel. • Relative cost, , fluctuates less over time than actual cost. Based on data in Appendix C, Callister, 7e . = Aramid, Glass, & Carbon fiber reinforced epoxy composites. c material ref ) kg / ($ kg / $ = c Graphite/ Ceramics/ Semicond Metals/ Alloys Composites/ fibers Polymers Relative Cost ( c ) pl. carbon Au Si wafer PET Epoxy Nylon 6,6 0.05 0.1 5 100000 10000 20000 50000 5000 2000 1000 500 200 100 50 20 10 2 1 0.5 Steel high alloy Al alloys Cu alloys Mg alloys Ti alloys Ag alloys Pt Tungsten Al oxide Concrete Diamond Glass-soda Si carbide Si nitride PC LDPE,HDPE PP PS PVC Aramid fibers Carbon fibers E-glass fibers AFRE prepreg CFRE prepreg GFRE prepreg Wood Chapter 23 - 4 • Bar must not lengthen by more than δ under force F ; must have initial length L . • Maximize the Performance Index : -- Stiffness relation: -- Mass of bar: L E c F δ = 2 ( σ = E ε ) 2 Lc M ρ = • Eliminate the "free" design parameter, c : E FL M ρ δ = 2 ρ = E P specified by application minimize for small M (stiff, light tension members) STIFF TENSION MEMBERS F , δ L c c
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3 Chapter 23 - 5 • Bar must carry a force F without failing;
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This note was uploaded on 03/18/2010 for the course ME 2580 taught by Professor Vandenbrink during the Spring '08 term at Western Michigan.

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mse22 - CHAPTER 22: MATERIALS SELECTION AND DESIGN...

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