Characterization of Structure and Morphology

Mullens, Steven; Luyten, Jan; Zeschky, J.

doi:10.1002/3527606696.ch3a

Cited by 15 publications

(17 citation statements)

References 43 publications

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“…This implies the assumption of unit cell geometries. 18 Furthermore, if the microstructure results from a known mechanism, it is appealing to directly incorporate this knowledge in the simulation procedure. 19 For instance, foams generally result from the nucleation, growth, and expansion of gas bubbles in a melt or reacting liquid system.…”

Section: A Basic Inverse 2d Foam Model Geometrymentioning

confidence: 99%

Dynamic viscous permeability of an open-cell aluminum foam: Computations versus experiments

Perrot

Chevillotte

Panneton

2008

Journal of Applied Physics

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Is it possible to find a two-dimensional ͑2D͒ periodic unit cell representative of the dynamic viscous dissipation properties of a real porous media? This is a challenging question addressed in this paper through a review of tools and methods of experimental and computational micro͑poro͒mechanics. The combination of advanced experimental imaging and numerical homogenization techniques provides a unique opportunity to understand and assess the limits of two-dimensional models of microstructures, as a potential basis for the engineering prediction of macroscopic properties of acoustical materials. This is illustrated for a real sample of open-cell aluminum foam. The conclusion, based on this analysis, is that the 2D periodic foam model geometry provides a reliable estimate of the dynamic permeability, except in the low frequency range. This is not surprising because in the 2D periodic foam model geometry, ligaments are always perpendicular to the flow direction, thus decreasing artificially the static permeability of the viscous flow.

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Section: A Basic Inverse 2d Foam Model Geometrymentioning

confidence: 99%

Dynamic viscous permeability of an open-cell aluminum foam: Computations versus experiments

Perrot

Chevillotte

Panneton

2008

Journal of Applied Physics

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“…Thresholding of the images, the most important stage in image analysis [28] was a simplified task in this case. Thresholding, employed as a segmentation technique, involves the distinction between those voxels which represent material and those which represent void.…”

Section: Methodsmentioning

confidence: 99%

“…pores per inch) and, more recently Visiocell ® were disregarded because these methods can be uncertain, with poor reproducibility and heavily dependent on users' input [28]. In the 'PPI method', number of pores is counted over a 1inch-long random line drawn on images of cross-sections.…”

Section: Morphological Characterization Of Density Gradation In the Pmentioning

confidence: 99%

Morphological and biological characterization of density engineered foams fabricated by ultrasonic sonication

Torres-Sánchez

Corney

2010

J Mater Sci

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“…are not necessarily identical from one manufacturer to another (Ref. 14). For example, some vendors specify the p.p.i.…”

Section: Introductionmentioning

confidence: 99%

Microstructural characterization of metal foams: An examination of the applicability of the theoretical models for modeling foams

Raj

2011

Materials Science and Engineering: A

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Establishing the geometry of foam cells is useful in developing microstructure-based acoustic and structural models. Since experimental data on the geometry of the foam cells are limited, most modeling efforts use the three-dimensional, space-filling Kelvin tetrakaidecahedron. The validity of this assumption is investigated in the present paper. Several FeCrAlY foams with relative densities varying between 3 and 15% and cells per mm (c.p.mm.) varying between 0.2 and 3.9 c.p.mm. were microstructurally evaluated. The number of edges per face for each foam specimen was counted by approximating the cell faces by regular polygons, where the number of cell faces measured varied between 207 and 745. The present observations revealed that 50 to 57% of the cell faces were pentagonal while 24 to 28% were quadrilateral and 15 to 22% were hexagonal. The present measurements are shown to be in excellent agreement with literature data. It is demonstrated that the Kelvin model, as well as other proposed theoretical models, cannot accurately describe the FeCrAlY foam cell structure. Instead, it is suggested that the ideal foam cell geometry consists of 11 faces with 3 quadrilateral, 6 pentagonal faces and 2 hexagonal faces consistent with the 3-6-2 cell. IntroductionAircraft engine noise is a major environmental concern especially in regions surrounding an airport during takeoff and landing (Ref. 1). Significant progress has been made since the advent of the first commercial jet engine-powered airplanes with current ultrahigh bypass engines being much quieter than the first generation engines. For example, the effective perceived noise level in decibels (EPNdB) relative to the International Civil Aviation Organization's (ICAO) Chapter 3 certification standards decreased from about +5 EPNdB for aircraft engines developed in the 1960s to -5 EPNdB for modern engines (Refs. 2 and 3). Despite this large improvement in engine design, there is still a great desire among policy makers and designers to reduce noise much below current levels. For example, the National Aeronautics and Space Administration (NASA) has set ambitious goals to further reduce aircraft noise by -52 db with respect to the newly adapted ICAO's Chapter 4 certification standards by the year 2020 under its Subsonic Fixed Wing (SFW) project (Ref. 4). It is expected that these noise reduction goals will be achieved through a combination of design changes and development of suitable materials (Refs. 3 and 4).Polymeric foams have been historically used for sound absorption in several applications (Ref. 5). More recently, metal foams are being investigated for their flow resistance (Refs. 6 and 7) and sound absorption properties (Refs. 8, 9, and 10). Metal foams have been proposed for use in jet engines as acoustic treatment over rotors (Ref. 11), fan blades (Ref. 12) and other applications (Ref. 13). The acoustic and other properties of foams are dependent on their relative density, */ s , where * and  s are the densities of the foam and the solid material, r...

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Characterization of Structure and Morphology

Cited by 15 publications

References 43 publications

Dynamic viscous permeability of an open-cell aluminum foam: Computations versus experiments

Dynamic viscous permeability of an open-cell aluminum foam: Computations versus experiments

Morphological and biological characterization of density engineered foams fabricated by ultrasonic sonication

Microstructural characterization of metal foams: An examination of the applicability of the theoretical models for modeling foams

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