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Selection of Materials

Selection of Materials. Selection of Materials. What qualities are important in your final product?. Light Cheap Strong enough to withstand expected forces Rigid Durable. Selection of Materials. How can we measure and compare these qualities?. Rupees per kilogram

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Selection of Materials

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  1. Selection of Materials

  2. Selection of Materials What qualities are important in your final product? • Light • Cheap • Strong enough to withstand expected forces • Rigid • Durable

  3. Selection of Materials How can we measure and compare these qualities? • Rupees per kilogram • Kg per m3 (Density) • Maximum Force (N) per m2 • Youngs Modulus • Toughness • Cost • Light/Heavy? • Strength • Rigid • Durable

  4. How light is my material? • Density is a measure of lightness • Density is the mass per unit volume wood steel water

  5. Density • Density is the mass per unit volume • Do polythene and PVC float or sink? Polythene PVC water

  6. Density • Density is the mass per unit volume 2 m 1 m Volume (m3) = x x 0.004 m • I have a mild steel sheet • The density is 7900 kg/m3 = 0.008 Mass (kg) = x 7900 kg/m3 0.008 m3 = 63 0.004 m thick 1m 2m

  7. 1 N 1 N How rigid is my material? The ‘Youngs Modulus’ is how we measure stiffness • Large Youngs Modulus • High Stiffness • Small Youngs Modulus • Low Stiffness

  8. How durable is my material? • During manufacture, materials will get small cracks • These cracks may get bigger very fast, or very slowly • Fatigue crack video • The tougher the material, the slower a small crack turns into a big crack glass steel

  9. How environmentally friendly is my material? • Energy used during manufacture • Often extracting a material can use a lot of energy • For example extracting aluminium requires a temperature of 2000 oC. • This uses up fuel resources, and also large processes need constant supplies of electricity, diverting power away from places such as Pabal.

  10. How environmentally friendly is my material? • 2) CO2 produced during manufacture • When we burn fuel/use electricity we release CO2 • CO2 contributes to global warming

  11. How environmentally friendly is my material? • Recyclability

  12. How strong must my material be? Wind Load = 8,9000N Self Weight = 1,4000N 6 10,3000N Force on 1 column = / 1,7000 N =

  13. How strong must my material be? • Strength is measured in N per square metre • Does this post have a cross section of 1 square metre? Load = 1,7000N Estimate Area Cross Section = 0.05m x 0.05m 5cm = 0.0025 m2 • How many 0.0025 m2’s fit into 1 square metre? 5cm • The force on 0.0025 m2 is 20,000 N • How much force is on 1 m2? = / 1 m2 0.0025 m2 400 = • 1m is 400 times bigger than 0.0025 m2 Force (N/m2) = x 400 1,7000N = 6,800,000

  14. 2 1 Strength - Cost 6.8 MPa 3 4

  15. Strength - Cost

  16. 1 2 3 4 Density - Cost

  17. Density - Cost

  18. 1 2 Strength - Density 3 4

  19. Strength - Density

  20. 2 1 Stiffness - Density 3 4

  21. Stiffness - Density

  22. 1 2 Toughness - Density 3 4

  23. Toughness - Density

  24. Yes Recycle False Price (£/kg) 2 1 Recycle - Cost 3 4

  25. Recycle - Cost

  26. Energy Required for production (MJ/kg) Price (£/kg) 1 2 3 4 Price - Energy

  27. Price - Energy

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