Advanced Engineering Materials

Cover image for Vol. 8 Issue 9

Special Issue: Metal Foams

September, 2006

Volume 8, Issue 9

Pages 767–912

Issue edited by: H. Nakajima, N. Kanetake

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Reviews
    5. Research News
    1. Cover Picture: The Structure of Random Foam (Adv. Eng. Mater. 9/2006)

      A. M. Kraynik

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200690018

      The unique physical properties of solid foams can be attributed to random cellular morphology, which usually forms in the liquid state when gas bubbles become highly concentrated. Key topological and geometric properties that characterize foam microstructure are evaluated from realistic models of soap froth that are simulated with Brakke's Surface Evolver.

  2. Contents

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Reviews
    5. Research News
    1. Contents: Adv. Eng. Mater. 9/2006 (pages 767–772)

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200690017

  3. Reviews

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Reviews
    5. Research News
    1. Metal Foams: Production and Stability (pages 781–794)

      J. Banhart

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600071

      The stabilisation mechanism of metallic foams is still not fully understood. In order to facilitate discussion of foam stabilisation the various methods for making such foams are classified with respect to the mode of gas generation and the type of melt used for foaming. Metal foams can be produced by gas injection from an external source or by in-situ nucleation of gas bubbles in the melt for which various possibilities are known. Melts amenable to foaming range from almost pure molten alloys to melts to which particles have been added, formed by in-situ reactions or which have been already present in the solid precursor prior to melting. Some of the available experimental evidence for the action of stabilising particles in metallic foams is presented.

    2. Replication Processing of Highly Porous Materials (pages 795–803)

      Y. Conde, J.-F. Despois, R. Goodall, A. Marmottant, L. Salvo, C. San Marchi and A. Mortensen

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600077

      The article gives an review of the state-of-the-art for the Replication process as it is practiced for the production of microcellular metals or ceramics. It includes a general description of the process and its variants and gives a brief overview of fundamentals, placing particular focus on pathways it offers for microstructural tailoring and control.

  4. Research News

    1. Top of page
    2. Cover Picture
    3. Contents
    4. Reviews
    5. Research News
    1. Density-Graded Cellular Aluminum (pages 805–809)

      A. H. Brothers and D. C. Dunand

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600074

      Open-cell metallic foams with controlled, continuous density gradients were created from polyurethane foam precursors using an investment casting method. This method, designed to improve mass-efficiency in load-bearing metallic foams and facilitate bonding of foams to dense materials in higher-order structures, is described in detail, and demonstrated through pure aluminum foams with model relative density gradients. Methods for structural characterization, including non-destructive local density mapping, are also illustrated.

    2. The Effect of Compaction Method on the Expansion and Stability of Aluminium Foams (pages 810–815)

      S. Asavavisithchai and A. R. Kennedy

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600067

      The foam expansion and collapse behaviour for heat treated Al-TiH2 precursors has been shown to be driven by the oxidation of the Al powder, which can, in moderation, improve the foam expansion and increase foam stability, and the premature loss of gas from the TiH2, which delays but decreases the foam expansion. The evidence presented indicates that as long as theoretical precursor densities >99% can be achieved, simultaneous heating and compaction are not required to achieve the best foaming behaviour. Instead, the oxygen or oxide content in the powder is critical and if the oxygen content in the atomised powder is in the range 0.3–0.4 wt.%, cold compaction is sufficient to produce foams which show expansions at least as good as those for precursors made by high cost hot working processes.

    3. Ultrasonically Welded Aluminium Foams/Sheet Metal – Joints (pages 816–820)

      C. Born, G. Wagner and D. Eifler

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600083

      The ultrasonic welding technology enables to produce high-strength joints between sheet metal and aluminium foam sandwich (AFS) without melting of the metal or any damage of the foam structure. In the investigations the used welding processes and different factors influencing the weldability, like the foam density, were varied. The achievable mechanical properties for ultrasonically welded metal joints, especially under monotonic and cyclic load, are discussed. Additionally, results of microscopic investigations of the bonding zone and possible applications are presented.

    4. Isothermal and Thermomechanical Fatigue Behavior of Open-Cell Metal Sponges — Experimental Analysis and Homogenization Modeling (pages 821–827)

      U. Krupp, A. Ohrndorf, T. Guillén, H.-J. Christ, S. Demiray, W. Becker and J. Hohe

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600081

      Fatigue experiments on open-cell metal sponges revealed that cyclic creep followed by macroscopic fatigue crack propagation due to cell strut cracking are the most relevant fatigue-life-determining damage mechanisms. In a meso-scale mechanical model developed, applying a strain-energy based homogenization approach for a 3-D Kelvin foam, fatigue damage is accounted for by stepwise removing cell struts leading to a pronounced reduction of the specimen's stiffness in the tensile half-cycle.

    5. Production and Fabrication Technology Development of Aluminum Useful for Automobile Lightweighting (pages 828–835)

      K. Ito and H. Kobayashi

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600072

      To undertake the development of technology to increase consumption of aluminum in passenger cars for improved fuel economy through lightweighting of cars as a measure to control global warming. More specifically, R&D is conducted on the following R&D themes to develop a material with a high formability and a technology to join a steel material, as well as to establish a technology to create materials with a good shock absorption performance.

    6. Cell Structure Control of Porous Titanium Composite Synthesized by Combustion Reaction (pages 836–840)

      M. Kobashi, K. Kuze and N. Kanetake

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600089

      Porous titanium matrix composites were fabricated by a combustion reaction between titanium powder and boron carbide (B4C) powder. The reaction products were titanium boride and titanium carbide. The combustion synthesized material was porous and its cell structure was strongly affected by the processing condition. The cell size was varied from several tens of microns to about 500 microns by changing the combustion temperature.

    7. Elastic Response of Titanium Foams During Compression Tests and Using Laser-Ultrasonic Probing (pages 841–846)

      L.-P. Lefebvre, A. Blouin, S.-M. Rochon and M. N. Bureau

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600080

      The elastic properties of titanium foams were evaluated using compression tests and the measurements of the specimen's resonance frequencies using laser-ultrasonics. The values measured by the two methods are in good agreement. Laser-ultrasonic techniques can be useful to measure the elastic modulus and Poisson's ratio of underformed specimens. The technique can be particularly valuable to evaluate the properties on small specimens.

    8. Iron Based Cellular Structures – Status and Prospects (pages 847–852)

      G. Stephani, O. Andersen, H. Göhler, C. Kostmann, K. Kümmel, P. Quadbeck, M. Reinfried, T. Studnitzky and U. Waag

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600078

      Cellular metals based on iron have been intensively investigated during the last two decades. Because of the significant decreasing of the structural density of iron based cellular structures, numerous technologies have been developed for their manufacturing. Besides the tremendous weight reduction a combination with other properties like energy and noise absorption, heat insulation and mechanical damping can be achieved. This contribution will give an overview about the latest state in iron based cellular materials, including technologies in manufacturing, properties and potential applications.

    9. Characterization and Mechanical Behavior of Nanoporous Gold (pages 853–857)

      A. M. Hodge, J. R. Hayes, J. A. Caro, J. Biener and A. V. Hamza

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600079

      Here the authors present current issues in understanding the mechanical behavior of nanoporous foams as a new class of high yield strength/low density materials. Gold nanoporous foams are used for a systematic study of mechanical properties since they can be synthesized with a wide range of ligaments sizes and densities. Preliminary tests demonstrate that a) Au foams have a fracture behavior dictated by the ligament size, and b) nanoporous Au is a high yield strength material.

    10. Machine Tools With Metal Foams (pages 858–863)

      R. Neugebauer and T. Hipke

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600095

      Today's machine tool construction calls for a extreme light weight construction with excellent dynamic properties. Modern frame components achieve this with metal foam components. They are breaking down solid steel structure into wide-area sandwich designs such as steel-aluminum foam-steel panels. Newest developments show the way from prototype manufacturing to a real serial production of machine tool components.

    11. Powder Compaction Effect on Foaming Behavior of Uni-Axial Pressed PM Precursors (pages 864–869)

      L. Bonaccorsi and E. Proverbio

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600082

      In metal foams prepared by the powder metallurgical (PM) route the precursor densification is fundamental for the obtainment of high quality final products. Precursor compaction is the result of several densification operations that play a significant role in the final production cost. The foaming behaviour of metal powder precursors compacted only by cold uni-axial compression was studied. It is shown how in controlled conditions of densification and foaming it is possible to produce good quality foamed products.

    12. Yield Functions for Porous Materials with Cubic Symmetry Using Different Definitions of Yield (pages 870–876)

      D. L. S. McElwain, A. P. Roberts and A. H. Wilkins

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600075

      Plastic yield criteria for porous ductile materials containing spherical voids in cubic arrays are investigated using finite-element analysis. Two definitions of yield are explored. An extension of the Gurson-Tvergaard-Needleman formula with no extra parameters fits the data well and is valid for all void volume fractions and triaxial stress states. Simple cubic structures are more resistant to shear, while body-centred and face-centred structures are more resistant to hydrostatic pressure.

    13. The Mechanism of Strength Enhancement under Impact Loading of Cellular Materials (pages 877–883)

      H. Zhao, I. Elnasri and H.J. Li

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600069

      Mechanical properties under impact loading of several metallic cellular materials (honeycombs, foams) are obtained with a Nylon SHPB. Significant enhancement under impact loading is observed for the materials having a crushing mode by successive buckling of the cell walls. A multiscale analysis performed on a model structure which is a square tube made of rate insensitive materials provide a satisfactory explanation of such strength enhancement by the lateral inertia effect.

    14. Experimental Techniques for the Investigation of the Elasto-Plastic Transition Zone of Foamed Materials (pages 884–889)

      A. Öchsner, T. Fiedler, J. Grácio and G. Kuhn

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600073

      The classical assumption in solid materials, i.e. that the plastic behaviour is incompressible, does no longer hold in the case of cellular materials. The plastic behaviour is pressure-sensitive due to the cellular structure. Therefore, the yield criterion needs to incorporate the hydrostatic pressure. The yield stress can be obtained from uniaxial tests but the determination of the weighting function for the hydrostatic stress requires the realisation of multi-axial stress states. This work presents two experimental procedures for the determination of the parameters of the yield criterion in the elasto-plastic transition zone.

    15. Experimental Analysis of Multiphase Flow in Metallic foam: Flow Laws, Heat Transfer and Convective Boiling (pages 890–899)

      F. Topin, J.-P. Bonnet, B. Madani and L. Tadrist

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600102

      Permeability and inertial coefficient are obtained using stationary pressure profile measurement in a channel filled with various metallic foams. Compressibility effects are studied. In single phase, heat transfer is X 100 with only a limited increase of pressure drop. Convective boiling regime showed significant heat transfer enhancement with very low-pressure drop. Global flow behavior across the test section is described by 1D homogeneous model.

    16. The Structure of Random Foam (pages 900–906)

      A. M. Kraynik

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600167

      The unique physical properties of solid foams can be attributed to random cellular morphology, which usually forms in the liquid state when gas bubbles become highly concentrated. Key topological and geometric properties that characterize foam microstructure are evaluated from realistic models of soap froth that are simulated with Brakke's Surface Evolver.

    17. Biocompatibility of Lotus-type Stainless Steel and Titanium in Alveolar Bone (pages 907–912)

      Y. Higuchi, Y. Ohashi and H. Nakajima

      Article first published online: 26 SEP 2006 | DOI: 10.1002/adem.200600124

      Lotus-type porous stainless steel (SUS304L) and porous titanium were fabricated by unidirectional solidification in a mixture gas of hydrogen and argon. The porous metals which were cut into cubes (non-dehydrogenated) and cylinders (dehydrogenated) were implanted into the canine mandible alveolar bone for two, four and eight weeks for animal experiments. The changes in the tissues were observed using SEM. The results lead the authors to expect application of the porous metals as biomaterials. They maintain mechanical strength and are lighter in weight so that it is expected to be applied for dental implants and core materials of artificial bones.

SEARCH

SEARCH BY CITATION