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Metal Foams: A Design Guide

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Appendix: Catalogue of material indices<br />

Material indices help to identify the applications in which a material might<br />

excel and those for generic components are assembled here. Their derivation<br />

and use is illustrated in Chapters 5, 11 and 12.<br />

(a) Stiffness-limited design at minimum mass (cost, energy a )<br />

Function and constraints a Maximize b<br />

SHAFT (loaded in torsion)<br />

Stiffness, length, shape specified, section area free G1/2 /<br />

Stiffness, length, outer radius specified; wall thickness free G/<br />

Stiffness, length, wall thickness specified, outer radius free G1/3 BEAM (loaded in bending)<br />

/<br />

Stiffness, length, shape specified; section area free E1/2 /<br />

Stiffness, length, height specified; width free E/<br />

Stiffness, length, width specified; height free E1/3 /<br />

COLUMN (compression strut, failure by elastic buckling) E1/2 buckling load, length, shape specified; section area free<br />

/<br />

a To minimize cost, use the above criteria for minimum weight, replacing density by Cm ,whereCm is the material cost per<br />

kg. To minimize energy content, use the above criteria for minimum weight replacing density by q where q is the energy<br />

content per kg.<br />

b E D Young’s modulus; G D shear modulus; D density.<br />

(b) Stiffness-limited design at minimum mass (cost, energy a )<br />

Function and constraints a Maximize b<br />

PANEL (flat plate, loaded in bending) E 1/3 /<br />

stiffness, length, width specified, thickness free<br />

PLATE (flat plate, compressed in-plane, buckling failure) E 1/3 /<br />

collapse load, length and width specified, thickness free

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