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modeling of the role of defects in sintered FeCrAlY foams

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Acta mechanica Sinica 2007年第5期23卷 511-529页

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

The metal sintering approach offers a costeffective means for the mass-production of open-cell foams from a range of materials, including high-temperature steel alloys, which offer novel mechanical and acoustic properties. In a separate experimental study, the mechanical properties of open-celled steel alloy （FeCrA1Y） foams have been characterized under uniaxial compression and shear loading. Compared to predictions from established models, a significant knockdown in material properties was observed. This knockdown was attributed to the presence of defects throughout the microstructure that result from the unique fabrication process. In the present paper, the microstructure of sintered FeCrA1Y foams was modeled by using a finite element （FE） model. In particular, microstructural variations were introduced to a base lattice, and the effects on the strength and stiffness calculated. A range of defects identified under scanning electronic microscope （SEm） imaging were considered including broken ligaments, thickness variations, and pore blockages, which are the three primary imperfections observed in sintered foams. The corresponding levels of defect present in the material were subsequently input into the FE model, with the resulting predictions correlating well with experimental data.

关键词： metal foam mechanical performance Defect Finite element SEm

Acoustic properties of sintered FeCrAlY foams with open cells (Ⅰ): Static flow resistance

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Science China(Technological Sciences) 2008年第11期51卷 1803-1811页

作者： m. kepets A. P. DOWLING Cambridge University Engineering Department Cambirdge CB2 1PZ U.K.

Open celled metal foams fabricated through the route of metal sintering are a new class of material that offers novel mechanical and acoustic properties. The metal sintering approach offers a cost-effective means for the mass-production of open-cell foams from a range of materials, including high-temperature steel alloys. The mechanical properties of open-celled steel alloy (FeCrAlY) foams have been characterized in previous studies, with focus placed on the influence of processing defects on stiffness and strength. In this work, the low-Reynolds number fluid properties of FeCrAlY foams were investigated both theoretically and experimen- tally. Specifically, the static flow resistance of the sintered foams important for heat transfer, filtration and sound absorption was modeled based on a cylinder and a sphere arranged in a periodic lattice at general incidence to the flow. Experimental measurements were subsequently carried out to validate theoretical predictions, with good agreement achieved.

关键词： metal foam static flow resistance modeling experiment

Acoustic properties of sintered FeCrAlY foams 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 Cambridge University Engineering Department Cambirdge CB2 1PZ U.K.

Open-celled metal foams fabricated through metal sintering offers novel mechani- cal, thermal and acoustic properties. Previously, polymer foams were used as a means of absorbing acoustic energy. However, the structural applications of these foams are inherently limited. The metal sintering approach provides a cost-effective means for the mass-production of open-cell foams from a range of materials, in- cluding high-temperature steel alloys. The low Reynolds number fluid properties of sintered steel alloy (FeCrAlY) foams were investigated in a previous study. The static flow resistance of the foams was modeled 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 measurements. The application of the flow resis- tance in an acoustic model is the primary focus of the present study. The predic- tions for the static flow resistance of the sintered foams are first used in a theo- retical model to determine the characteristic impedances, as well as the propaga- tion constants of the foams. Subsequently, the predicted acoustic performance of the foams is compared to experimental results. Finally, the design space for a simple acoustic absorber incorporating sintered foams is examined, with the ef- fects of absorber size, foam selection, and foam spacing explored.

关键词： metal foam sound absorption modeling experiment acoustic design