An investigation of the microstructure and strength of open-cell 6101 aluminum foams

Zhou, Jianxin; Mercer, C.; Soboyejo, W. O.

doi:10.1007/s11661-002-0065-x

Cited by 63 publications

(35 citation statements)

References 32 publications

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“…The use of synchrotron radiation CT, allowing the acquisition of high resolution three-dimensional images with a cubic voxel size less than 1 m, is then required. 22 It is also worth mentioning that, when such a tool is not available, quantitative results of the cellular morphology can be obtained by a destructive but accurate optical microscopy and stereological image analysis based method, 6 which was found to give results in excellent agreement with those in the present article.…”

Section: B Representativity and Limitationssupporting

confidence: 78%

“…7 compares the mean results given in Table III to results on ERG foams that can be found in the literature. The comparisons are in terms of ligament length, 6 ligament thickness, 6,8,9 and characteristic radii. 6,8 It is worth noting that Schmierer et al 9 have measured the ligament hydraulic diameter D h , whereas in Zhou et al 6 and Scheffler et al 8 While this method offers a new way of identifying the microstructural parameters of an open-cell foam, it has some limitations.…”

Section: B Representativity and Limitationsmentioning

confidence: 99%

“…5 Several authors have reported experimental studies of local geometry properties of fully saturated high porosity open-cell metal foams. [6][7][8][9] Zhou et al 6 have investigated the morphology of foams from a mechanical property analysis viewpoint. They presented principal cell diameter, ligament thickness, and ligament length data for three combinations of porosity and pore density.…”

Section: Introductionmentioning

confidence: 99%

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Periodic unit cell reconstruction of porous media: Application to open-cell aluminum foams

Perrot

Panneton

Olny

2007

Journal of Applied Physics

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In this article, the issue of reconstructing an idealized periodic unit cell ͑PUC͒ to represent a porous medium is examined by means of microcomputed tomography ͑ CT͒. Using CT, three-dimensional images of open-cell foam are collected and used to characterize the representative parameters of its cellular morphology. These parameters are used in order to reconstruct the porous medium by means of an idealized PUC: a tetrakaidecahedron with ligaments of triangular cross sections, whose characteristic dimensions have been measured on the CT images. The proposed reconstruction of the idealized PUC is applied to four aluminum foams. The averaged macroscopic properties of the foams ͑open porosity and thermal characteristic length͒ are deduced from their respective PUC model and compared to experimental measurements and literature data. Good correlations are obtained. For each of the foams, this provides a parameterized idealized periodic unit cell on which the partial differential equations governing sound dissipation and propagation in foams can be solved with a view to studying the microphysical basis of the acoustical macrobehavior.

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Section: B Representativity and Limitationssupporting

confidence: 78%

Section: B Representativity and Limitationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Periodic unit cell reconstruction of porous media: Application to open-cell aluminum foams

Perrot

Panneton

Olny

2007

Journal of Applied Physics

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“…Also, during tension and compression tests, a more detailed characterization of the foam's geometry is required to understand bending, elongation, buckling, and final collapse. 23 Probably the most accurate foam model can be obtained via microcomputed tomography scan (lCT). However, computational restrictions only allow for limited volumes to be analyzed.…”

Section: -mentioning

confidence: 99%

An experimentally validated and parameterized periodic unit-cell reconstruction of open-cell foams

Jaeger

T’Joen

Huisseune

et al. 2011

Journal of Applied Physics

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The physical behavior of open-cell foams depends on their microscopic structure. An open-cell geometrical model is proposed, which can serve as the basis for a future macroscopic analysis. The strut geometry is of particular interest, as it is reported to have substantial influence on the occurring thermo-hydraulic and mechanical phenomena. Axial strut size variation, as well as the porosity dependence of shape is quantified and included in a geometrical model. The foam is generated by placing the struts on an elongated tetrakaidecahedron. The required input parameters for the model are two cell dimensions, corresponding to the mean transverse and conjugate diameters of the ellipse encompassing a cell, and the strut cross-sectional surface area at its midpoint between two nodes. The foam geometry is generated iteratively, as porosity is used as validation. A high resolution micro-computed tomography scan is performed to measure the three parameters, the resulting porosity and surface-to-volume ratio. This allows to validate the model. The predictions are found to be within measurement accuracy. A numerical implementation of the model in the preprocessor of a commercial CFD package is demonstrated.

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“…Metals are much more likely to be able to meet these requirements than ceramics. Moreover, while many types of highly porous metal exhibit relatively poor toughness (under tensile loading) and mechanical durability, [17][18][19][20] metallic fibre network materials can be relatively strong and tough, particularly if the fibre-fibre joints are strong. [21] Of course, a low overall density is highly desirable, to minimise the mass of the module.…”

mentioning

confidence: 99%

Ferrous Fibre Network Materials for Jet Noise Reduction in Aeroengines Part I: Acoustic Effects

2008

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Noise emitted by gas turbine aeroengines is of major concern. For turbofan engines, it comes from two main sourcesthe rotational motion of the system (fan, compressor and turbine) and gas mixing phenomena associated with the jet emerging from the rear of the engine ("jet noise"). Most rotation-generated noise occurs at well-defined frequencies (dependent on engine speed), whereas jet noise tends to be more broadband. Fan/compressor/turbine noise normally dominates during landing and is of comparable amplitude to jet noise during cruising. Fan noise can be reduced by using acoustic liners and by redesigning the inlet lip to make the inner wall of the nacelle sound-absorbent, and by reshaping the fan blades -for example so that they tend to dissipate local shockwaves.Jet noise (including any contributions from mixing of core/combustion and by-pass streams) is mainly associated with turbulent flow in the exhaust region. It is the dominant acoustic source during take-off, and is hence of prime concern. Unfortunately, jet noise is hard to control, since any measures must exert their effect before the exhaust leaves the engine. In fact, Lighthill's eighth power law (linking noise intensity to gas velocity), and its consequence of high-bypass ratio (low gas velocity) engines tending to allow lower noise levels for a given thrust, remains a pre-eminent design guideline. Other design changes aimed at reducing jet noise have had limited success. Recent developments include nozzle designs incorporating chevrons [1,2] to control mixing of core and by-pass streams and exhaust designs promoting mixing of core, by-pass and ambient airflows, both of which are reported to give up to ∼ 3 dB noise reduction. Broadband noise reduction can also be achieved using active absorption systems, [3,4] but these rely on rapid and complex feedback control. In general, they are considered unlikely to be effective on most aircraft, at least in the near future.Increased exhaust containment length, with a module made of a suitable acoustic attenuation material in the enclosed region, has good potential for reduction of jet noise. Open cell porous materials are promising candidates. Acoustic absorption within them [5][6][7] results mainly from drag on acoustic waves as they propagate through narrow, tortuous channels. The frequency characteristics of such absorption should be taken into account, and related to the frequency sensitivity of the human ear. The well known Fletcher-Munson curves [8] indicate maximum sensitivity at around 1-6 kHz. Frequencies below a few hundred Hz and above ∼ 10 kHz are unlikely to be problematic. There have been relatively few studies on the effect of the architecture of porous materials on the frequency dependence of their sound absorption characteristics. Xie et al. [7] did, however, report that, in their work on directionally-solidified porous copper with porosity in the approximate range of 40-60 %, sound absorption increased with increasing frequency, from a low level below ∼ 1 kHz to a broad peak somewhere betw...

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An investigation of the microstructure and strength of open-cell 6101 aluminum foams

Cited by 63 publications

References 32 publications

Periodic unit cell reconstruction of porous media: Application to open-cell aluminum foams

Periodic unit cell reconstruction of porous media: Application to open-cell aluminum foams

An experimentally validated and parameterized periodic unit-cell reconstruction of open-cell foams

Ferrous Fibre Network Materials for Jet Noise Reduction in Aeroengines Part I: Acoustic Effects

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