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Acoustic properties of sintered FeCrAlY foam. with open cells (Ⅱ): Sound attenuation

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Science China(Technological Sciences) 2008年第11期51卷 1812-1837页

作者： m. kepets A. P. DOWLING2 Cam.ridge University Engineering Departm.nt Cambirdge CB2 1PZ U.K.

Open-celled m.tal foam. fabricated through m.tal sintering offers novel m.chani- cal, therm.l and acoustic properties. Previously, polym.r foam. were used as a m.ans of absorbing acoustic energy. However, the structural applications of these foam. are inherently lim.ted. The m.tal sintering approach provides a cost-effective m.ans for the m.ss-production of open-cell foam. from.a range of m.terials, in- cluding high-tem.erature steel alloys. The low Reynolds num.er fluid properties of sintered steel alloy (FeCrAlY) foam. were investigated in a previous study. The static flow resistance of the foam. was m.deled based on a cylinder and a sphere arranged in a periodic lattice at general incidence to the flow, with the resulting predictions correlating well to m.asurem.nts. The application of the flow resis- tance in an acoustic m.del is the prim.ry focus of the present study. The predic- tions for the static flow resistance of the sintered foam. are first used in a theo- retical m.del to determ.ne the characteristic im.edances, as well as the propaga- tion constants of the foam.. Subsequently, the predicted acoustic perform.nce of the foam. is com.ared to experim.ntal results. Finally, the design space for a sim.le acoustic absorber incorporating sintered foam. is exam.ned, with the ef- fects of absorber size, foam.selection, and foam.spacing explored.

关键词： m.tal foam sound absorption m.deling experim.nt acoustic design

m.chanical characterization of the role of defects in sintered FeCrAIY foam.

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Acta m.chanica Sinica 2007年第4期23卷 383-398页

作者： m.kepets A.P.Dowling Engineering Departm.nt Cambridge UniversityCambridge CB2 1PZUK

Open celled m.tal foam. fabricated through m.tal sintering are a new class of m.terial that offers novel m.chanical and acoustic properties. Previously, polym.r foam. have been widely used as a m.ans of absorbing acoustic energy. However, the structural applications of these foam. are lim.ted. The m.tal sintering approach offers a costeffective m.ans for the m.ss-production of open-cell foam. from.a range of m.terials, including high-tem.erature steel alloys. In this first part of two-paper series, the m.chanical properties of open-celled steel alloy （FeCrA1Y） foam. were characterized under uniaxial com.ression and shear loading. Com.ared to predictions from.established m.dels, a significant knockdown in m.terial properties was observed. This knockdown was attributed to the presence of defects throu- ghout the m.crostructure that result from.the unique fabrication process. Further in situ tests were carried out in a SEm.（scanning electronic m.croscope） in order to investigate the effects of defects on the properties of the foam.. Typically, the onset of plastic yielding was observed to occur at defect locations within the m.crostructure. At lower relative densities, ligam.nt bending dom.nates, with the deform.tion initializing at defects. At higher relative densities, an additional deform.tion m.chanism.associated with m.m.rane elem.nts was observed. In the follow-up of this paper, a finite elem.nt m.del will be constructed to quantify the effects of defects on the m.chanical perform.nce of the opencell foam.

关键词： m.tal foam Defect m.chanical characterization SEm

m.deling of the role of defects in sintered FeCrAlY foam.

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Acta m.chanica Sinica 2007年第5期23卷 511-529页

作者： m.kepets T.J.Lu A.P.Dowling Cam.ridge University Engineering Departm.nt Cambridge CB2 1PZUK m.E Key Laboratory of Strength and Vibration School of AerospaceXi'an Jiaotong UniversityXi'an 710049China

The m.tal sintering approach offers a costeffective m.ans for the m.ss-production of open-cell foam. from.a range of m.terials, including high-tem.erature steel alloys, which offer novel m.chanical and acoustic properties. In a separate experim.ntal study, the m.chanical properties of open-celled steel alloy （FeCrA1Y） foam. have been characterized under uniaxial com.ression and shear loading. Com.ared to predictions from.established m.dels, a significant knockdown in m.terial properties was observed. This knockdown was attributed to the presence of defects throughout the m.crostructure that result from.the unique fabrication process. In the present paper, the m.crostructure of sintered FeCrA1Y foam. was m.deled by using a finite elem.nt （FE） m.del. In particular, m.crostructural variations were introduced to a base lattice, and the effects on the strength and stiffness calculated. A range of defects identified under scanning electronic m.croscope （SEm. im.ging were considered including broken ligam.nts, thickness variations, and pore blockages, which are the three prim.ry im.erfections observed in sintered foam.. The corresponding levels of defect present in the m.terial were subsequently input into the FE m.del, with the resulting predictions correlating well with experim.ntal data.

关键词： m.tal foam m.chanical perform.nce Defect Finite elem.nt SEm