Despite this dire warning the two charts are

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Despite this dire warning, the two charts are genuinely useful. They allow selection of materials using the criterion of function per unit cost. An example is given in Section 6.5. 4.4 SUMMARY AND CONCLUSIONS The engineering properties of materials are usefully displayed as material selection charts. Eighteen of them are introduced in this chapter; more appear in later ones. The charts summarize material properties in a compact, easily accessible way, showing the range spanned by each material family and class. By choosing the axes in a sensible way, more information can be displayed. A chart of modulus E against density ρ reveals the longitudinal wave velocity ð E / ρ Þ 1/2 . A chart of fracture toughness K 1 c against modulus E shows the Relative cost per unit volume C v , R Young’s modulus E (GPa) 0.01 0.1 1 10 100 0.01 0.1 1 10 100 10,000 Foams Polymers Metals Technical ceramics Composites Natural materials Lead alloys W alloys Carbon steels Mg alloys CFRP GFRP Al alloys Rigid polymer foams Zinc alloys PS PTFE PC Wood Concrete Al 2 O 3 SiC Modulus – Relative cost/volume PP EVA Leather MFA, 09 Cast irons WC Soda glass Silica glass Silicon Brick ABS Ionomers AlN PEEK PE PMMA Polyurethanes Acetal // grain grain Elastomers C v , R E 1/3 C v , R E 1/2 C v , R E Guide lines for minimum cost design Nontechnical ceramics Flexible polymer foams Stone Stainless steels Si 3 N 4 B 4 C Ti alloys Silicone elastomers Polyurethane Epoxies FIGURE 4.18 Young s modulus E plotted against relative cost per unit volume C v,R . The design guide lines help selection to maximize stiffness per unit cost. 4.4 Summary and Conclusions 93
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toughness G 1 c . A chart of thermal conductivity λ against diffusivity, a , also gives the volume-specific heat ρ C v . A chart of strength, σ f , against modulus, E , shows the energy-storing capacity, σ 2 f / E , and there are many more. The most striking feature of the charts is the way in which members of a material class cluster together. Despite the wide range of modulus and density of metals (as an example), the clusters occupy a field that is distinct from that of polymers or that of ceramic, or that of composites. The same is true of strength, toughness, thermal conductivity, and the rest: The fields frequently overlap, but they always have a characteristic place within the whole picture. The position of the fields and their relationship can be understood in simple physical terms. The nature of the bonding, the packing density, the lattice resis- tance, and the vibrational modes of the structure are themselves a function of Strength σ f (MPa) 0.01 0.1 1 10 1000 0.01 0.1 1 10 100 1000 10,000 Relative cost per unit volume C v , R Foams Polymers and elastomers Metals Technical ceramics Natural materials Lead alloys W alloys Carbon steels Ti alloys CFRP GFRP Al alloys Rigid polymer foams Flexible polymer foams Cu alloys Zinc alloys PS PTFE Cork Wood Concrete Al 2 O 3 SiC Si 3 N 4 Strength – Relative cost/volume B 4 C PP Neolprene Leather Nontechnical ceramics MFA, 09 Cast irons WC Silica glass Silicon Stone Brick ABS Epoxies
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Christopher Reinemann
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