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

Abstract

Open-celled metal foams fabricated through metal sintering offers novel mechanical, 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, including 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 resistance in an acoustic model is the primary focus of the present study. The predictions for the static flow resistance of the sintered foams are first used in a theoretical model to determine the characteristic impedances, as well as the propagation 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 effects of absorber size, foam selection, and foam spacing explored. metal foam, sound absorption, modeling, experiment, acoustic design

Sound absorption of open celled aluminium foam fabricated by investment casting method

“…the approximate periodical absorptive resonant peaks appear as the sample thickness and the air gap depth increase. According to Lu et al ,17 the introduction of air gap will change the resonance modes of the specimen–tube system, and the resonant frequency f r is described by (Ref. 18) where c is the velocity of sound, A the cross-sectional area of the neck, L the neck length and V the volume of cavity.…”

Development of multifunctional lightweight cellular metals through interdisciplinary efforts

“…The static flow resistance of FeCrAlY foams important for heat transfer, filtration and sound absorption was modeled based on the flow past isolated inclined cylinders and spheres at general incidence, with the interaction between neighboring ligaments accounted for. The model predictions, confirmed by comparison with experimental measurements, were subsequently used by Lu et al [4] in a phenomenological acoustic model to predict the acoustic characteristics of the foams. The design space for a simple acoustic absorber incorporating sintered foams (targeting high temperature applications such as the acoustic liner of jet engines) was examined, with the effects of absorber size, foam selection, and foam spacing explored.…”

“…The base materials that have been considered include pure aluminum and its alloys, stainless steel, pure copper and its alloys, FeCrAlY, etc. The types of cellular metal reported in Science in China E include aluminum foams with closed cells [2] , sintered FeCrAlY foams with open cells [3,4] , phononic crystals [5] , pin-reinforced foams [6] , and lattice metals [7,8] . The development of these materials is not only to master the relevant fabrication technologies, but also to further address fundamental issues related to their processing, properties and practical applications using a combination of experimental, theoretical and numerical approaches.…”

Fourier Transform Sound Radiation

“…For instance, Lu et al proposed a model for high porosity cellular metallic foams with open cells [24,25,27,28] and another model for semi-open metal foams [26]. As for fibrous materials considered here, there are two main classes of models [19].…”