Metal Foams : A Design Guide

Metal foams are at the forefront of technological development for the automotive, aerospace, and other weight-dependent industries. They are formed by various methods, but the key facet of their manufacture is the inclusion of air or other gaseous pockets in the metal structure. the fact that gas pockets are present in their structure provides an obvious weight advantage over traditionally cast or machined solid metal components. The unique structure of metal foams also opens up more opportunities to improve on more complex methods of producing parts with space inclusions such as sand-casting. This guide provides information on the advantages metal foams possess, and the applications for which they may prove suitable.

Preface and acknowledgements

ix

List of contributors

xi

Table of physical constants and conversion units

xiii

Introduction

1

(5)

This Design Guide

1

(2)

Potential applications for metal foams

3

(2)

The literature on metal foams

5

(1)

Making metal foams

6

(18)

Making metal foams

6

(2)

Melt gas injection (air bubbling)

8

(1)

Gas-releasing particle decomposition in the melt

9

(2)

Gas-releasing particle decomposition in semi-solids

11

(1)

Casting using a polymer or wax precursor as template

11

(3)

Metal decomposition on cellular preforms

14

(1)

Entrapped gas expansion

14

(2)

Hollow sphere structures

16

(3)

Co-compaction or casting of two materials, one leachable

19

(1)

Gas--metal eutectic solidification

20

(1)

Literature on the manufacture of metal foams

20

(4)

Characterization methods

24

(16)

Structural characterization

24

(2)

Surface preparation and sample size

26

(1)

Uniaxial compression testing

27

(2)

Uniaxial tension testing

29

(1)

Shear testing

30

(1)

Multi-axial testing of metal foams

31

(3)

Fatigue testing

34

(1)

Creep testing

35

(1)

Indentation and hardness testing

35

(1)

Surface strain mapping

36

(2)

Literature on testing of metal foams

38

(2)

Properties of metal foams

40

(15)

Foam structure

40

(2)

Foam properties: an overview

42

(6)

Foam property charts

48

(4)

Scaling relations

52

(3)

References

54

(1)

Design analysis for material selection

55

(7)

Background

55

(1)

Formulating a property profile

56

(2)

Two examples of single-objective optimization

58

(3)

Where might metal foams excel?

61

(1)

References

61

(1)

Design formulae for simple structures

62

(18)

Constitutive equations for mechanical response

62

(2)

Moments of sections

64

(3)

Elastic deflection of beams and panels

67

(2)

Failure of beams and panels

69

(1)

Buckling of columns, panels and shells

70

(2)

Torsion of shafts

72

(2)

Contact stresses

74

(2)

Vibrating beams, tubes and disks

76

(2)

Creep

78

(2)

References

79

(1)

A constitutive model for metal foams

80

(8)

Review of yield behavior of fully dense metals

80

(2)

Yield behavior of metallic foams

82

(4)

Postscript

86

(2)

References

87

(1)

Design for fatigue with metal foams

88

(15)

Definition of fatigue terms

88

(2)

Fatigue phenomena in metal foams

90

(4)

S--N data for metal foams

94

(3)

Notch sensitivity in static and fatigue loading

97

(6)

References

101

(2)

Design for creep with metal foams

103

(10)

Introduction: the creep of solid metals

103

(2)

Creep of metallic foams

105

(1)

Models for the steady-state creep of foams

106

(1)

Creep data for metallic foams

107

(2)

Creep under multi-axial stresses

109

(1)

Creep of sandwich beams with metal foam cores

109

(4)

References

112

(1)

Sandwich structures

113

(37)

The stiffness of sandwich beams

113

(3)

The strength of sandwich beams

116

(4)

Collapse mechanism maps for sandwich panels

120

(3)

Case study: the three-point bending of a sandwich panel

123

(1)

Weight-efficient structures

124

(2)

Illustration for uniformly loaded panel

126

(7)

Stiffness-limited designs

133

(7)

Strength-limited designs

140

(8)

Recommendations for sandwich design

148

(2)

References

148

(2)

Energy management: packaging and blast protection

150

(21)

Introduction: packaging

150

(1)

Selecting foams for packaging

151

(6)

Comparison of metal foams with tubular energy absorbers

157

(4)

Effect of strain rate on plateau stress

161

(2)

Propagation of shock waves in metal foams

163

(3)

Blast and projectile protection

166

(5)

References

169

(2)

Sound absorption and vibration suppression

171

(10)

Background: sound absorption in structural materials

171

(2)

Sound absorption in metal foams

173

(2)

Suppression of vibration and resonance

175

(6)

References

179

(2)

Thermal management and heat transfer

181

(8)

Introduction

181

(1)

Heat transfer coefficient

182

(2)

Heat fluxes

184

(2)

Pressure drop

186

(1)

Trade-off between heat transfer and pressure drop

187

(2)

References

188

(1)

Electrical properties of metal foams

189

(5)

Measuring electrical conductivity or resistivity

189

(1)

Data for electrical resistivity of metal foams

190

(1)

Electrical conductivity and relative density

191

(3)

References

193

(1)

Cutting, finishing and joining

194

(6)

Cutting of metal foams

194

(1)

Finishing of metal foams

194

(1)

Joining of metal foams

195

(5)

References

199

(1)

Cost estimation and viability

200

(17)

Introduction: viability

200

(1)

Technical modeling and performance metrics

201

(1)

Cost modeling

202

(4)

Value modeling

206

(6)

Applications

212

(5)

References

216

(1)

Case studies

217

(17)

Aluminum foam car body structures

217

(2)

Integrally molded foam parts

219

(1)

Motorway sound insulation

220

(2)

Optical systems for space applications

222

(2)

Fluid--fluid heat exchangers

224

(1)

Lightweight conformal pressure tanks

225

(1)

Electrodes for batteries

225

(1)

Integrated gate bipolar transistors (IGBTs) for motor drives

226

(6)

Applications under consideration

232

(2)

Suppliers of metal foams

234

(5)

Web sites

239

(3)

Appendix: Catalogue of material indices

242

(5)

Index

247

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Metal Foams : A Design Guide

Summary

Table of Contents

Supplemental Materials