Metal Foams: A Design Guide

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20 Metal Foams: A Design Guide between 0.3 and 0.5. The cell size is determined by the powder particle size, and lies in the range 10 µm to 10 mm. In an alternative but closely related process, a bed of particles of the leachable material is infiltrated by liquid metal under pressure, and allowed to cool. Leaching of the particles again gives a cellular metallic structure of great uniformity. 2.10 Gas–metal eutectic solidification Numerous metal alloy–hydrogen binary phase diagrams exhibit a eutectic; these include Al-, Be-, Cr-, Cu-, Fe-, Mg-, Mn- and Ni-based alloys. The alloys are melted, saturated with hydrogen under pressure, and then directionally solidified, progressively reducing the pressure. During solidification, solid metal and hydrogen simultaneously form by a gas eutectic reaction, resulting in a porous material containing hydrogen-filled pores. These materials are referred to as GASARs (or GASERITE). A schematic diagram of the basic approach is shown in Figure 2.10. A furnace placed within a pressure vessel is used to melt an alloy under an appropriate pressure of hydrogen (typically 5–10 atmospheres of hydrogen). This melt is then poured into a mold where directional eutectic solidification is allowed to occur. This results in an object containing a reasonably large (up to 30%) volume fraction of pores. The pore volume fraction and pore orientation are a sensitive function of alloy chemistry, melt over-pressure, melt superheat (which affects the hydrogen solubility of the liquid metal), the temperature field in the liquid during solidification, and the rate of solidification. With so many process variables, control and optimization of the pore structure are difficult. The method poses certain safety issues, and in its present form is a batch process. As a result, materials manufactured by this route are costly. Though GASAR materials were among the first highly porous materials to attract significant interest, they remain confined to the laboratory and are not yet commercially available. 2.11 Literature on the manufacture of metal foams General Astro Met, Inc. Ampormat Porous Materials, Astro Met, Inc., Cinncinnati. Davies, G.J. and Zhen, S. (1983) Metallic foams: their production, properties, and applications. Journal of Materials Science 18 1899–1911. Banhart, J. and Baumeister, J. (1988) Production methods for metallic foams. In Shwartz, D.S., Shih, D.S., Evans, A.G. and Wadley, H.N.G. (eds) (1998) Porous and Cellular Materials for Structural Application, Materials Research Society Proceedings, Vol. 521, MRS, Warrendale, PA, USA.
a) Metal - Hydrogen binary phase diagram Temperature, T Pressure, P Solid Liquid Solid + Liquid Eutectic Solid + H 2 Metal wt% H 2 b) Directional solidification Pressure, P H 2 c) Final pore structure AR + H 2 Liquid + H 2 Stop rod Crucible Mold Heating Making metal foams 21 Figure 2.10 Gas–metal eutectic solidification for the manufacture of GASARs
Page 1 and 2: Metal Foams: A Design Guide
Page 3 and 4: Copyright © 2000 by Butterworth-He
Page 5 and 6: vi Contents 4.3 Foam property chart
Page 7 and 8: viii Contents 17 Case studies 217 1
Page 9 and 10: List of contributors M.F. Ashby Cam
Page 11 and 12: Table of physical constants and con
Page 13 and 14: Chapter 1 Introduction Metal foams
Page 15 and 16: Activity Research Industrial take-u
Page 17 and 18: Application Comment Introduction Bi
Page 19 and 20: Cell size (cm) Making metal foams 7
Page 21 and 22: Making metal foams solidify. The th
Page 23 and 24: Making metal foams 11 2.4 Gas-relea
Page 25 and 26: a) Preform Polymer ligaments d) Rem
Page 27 and 28: a) Vapor deposition of Nickel b) Bu
Page 29 and 30: Process Steps a) Powder / Can prepa
Page 31: Making metal foams 19 flight in a t
Page 35 and 36: Entrapped gas expansion Making meta
Page 37 and 38: (a) (b) (c) 100µm Characterization
Page 39 and 40: E/E bulk σ peak /σ bulk 1.2 1.0 0
Page 41 and 42: Stress (MPa) Characterization metho
Page 43 and 44: Characterization methods 31 foam sp
Page 45 and 46: Characterization methods 33 ž Prop
Page 47 and 48: F/2 F/2 F/2 F/2 τ Core Characteriz
Page 49 and 50: Characterization methods 37 40 40 4
Page 51 and 52: Characterization methods 39 Gioux,
Page 53 and 54: (a) (b) (c) Properties of metal foa
Page 55 and 56: Table 4.1 (a) Ranges a for mechanic
Page 57 and 58: Stress, σ Schematic Young's modulu
Page 59 and 60: Properties of metal foams 47 foams.
Page 61 and 62: Properties of metal foams 49 show t
Page 63 and 64: Modulus 0.5 /Density (GPa 0.5 /(Mg/
Page 65 and 66: elations take the form P Ł � Ł
Page 67 and 68: Chapter 5 Design analysis for mater
Page 69 and 70: Table 5.1 Design requirements Desig
Page 71 and 72: Design analysis for material select
Page 73 and 74: 5.4 Where might metal foams excel?
Page 75 and 76: Table 6.1 Constitutive equations fo
Page 77 and 78: h SECTION h o h i d d o a b ;;; QQQ
Page 79 and 80: 6.3 Elastic deflection of beams and
Page 81 and 82: 6.4 Failure of beams and panels (a)
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;; ;;; ;; M ;; ;;; ;; ;;; ;; ;; ;;
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Torsion of shafts T T,q T T,q Yield
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R a 2 Flow field R F R 2a 2 F F s c
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;; ; QQ Q ¢¢ ¢ ;; ;; QQ QQ ¢¢
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; ;; Creep p e p e • Area A u F 2
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and its deviatoric (i.e. shear) com
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Normalized effective stress 1.4 1.2
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A constitutive model for metal foam
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A constitutive model for metal foam
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Stress amplitude, ∆σ + Stress,
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Axial strain (%) 5 4 3 2 1 0 0 σma
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Nominal compressive strain Nominal
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σ max σ pl τ max τ pl σ max σ
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Design for fatigue with metal foams
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the net section stress criterion re
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E σ pl (m) 10 1 0.1 0.01 0.1 Relat
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Chapter 9 Design for creep with met
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Design for creep with metal foams 1
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instead to: � Pε 3 D Pε0 2 s Ł
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Time to failure (hours) 10 2 10 1 1
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Design for creep with metal foams 1
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Chapter 10 Sandwich structures Sand
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Sandwich structures 115 The elastic
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Indentation Sandwich structures 117
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H H Core shear Core shear Collapse
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0.5 10−1 t c t c 10 −2 0.5 10
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Sandwich structures 123 the contact
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Sandwich structures 125 four sectio
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c t p p Figure 10.9 Sandwich panel
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Sandwich structures 129 with k ¾ D
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c/ Face sheet yielding 0.14 0.12 0.
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Weight index, ψ 10 −1 10 −2 10
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Sandwich structures 135 To construc
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Sandwich structures 137 The associa
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Sandwich structures 139 Note that,
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where D � 2⊲1 Eft 2 f ⊳GcR Sa
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Weight index ψ = W/2πR 2 ρ s W c
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Sandwich structures 145 plastic yie
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Sandwich structures 147 within the
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Sandwich structures 149 Shuaeib, F.
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Energy management: packaging and bl
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Energy/Unit cost (kJ/£) 10 1 0.1 0
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ys crushes axially at the load Ener
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peak pressure MPa Impulse/(mass of
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Chapter 12 Sound absorption and vib
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Sound absorption and vibration supp
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0 Sound absorption and vibration su
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Chapter 13 Thermal management and h
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Thermal management and heat transfe
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Thermal management and heat transfe
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~ P ~ Re 2.6 1000 800 600 400 200 0
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Chapter 14 Electrical properties of
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Electrical properties of metal foam
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Electrical properties of metal foam
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15.3 Joining of metal foams Cutting
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Pull-out load, F p (N) 10 5 10 4 10
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Cyclic loading of fasteners Cutting
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Time, material, energy, capital, in
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Cost estimation and viability 203 A
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$/Unit Melting Schematic of the liq
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Performance metric, P2 B Non-domina
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Cost estimation and viability 209 t
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Cost estimation and viability 211 i
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P 2 = 1/Loss coefficient (−) 1000
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Cost estimation and viability 215 C
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Chapter 17 Case studies Metal foams
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Case studies 219 Figure 17.2 A pres
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Case studies 221 Figure 17.4 Highwa
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Case studies 223 Figure 17.6 DUOCEL
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Case studies 225 density and high t
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Case studies 227 required for compa
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Maximum power density at electronic
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q *(MW/m 2) 15 10 Power density fix
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Case studies 233 which optimized sk
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e-mail: cymat@ican.net Web: www.cym
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Tel: C0043 7722 801-2125 Fax: C0043
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Chapter 19 Web sites An increasing
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http://www.seac.nl/english/recemat/
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(b) (continued) Appendix: Catalogue
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(f) Vibration-limited design Append
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Index (Company and trade names are
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Heat transfer 4, 182 Heat transfer
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Surface strain mapping 36 Syntactic
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Metal Foams: A Design Guide

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