Lu T J, Chen F, He D
Engineering Department, Cambridge University, United Kingdom.
J Acoust Soc Am. 2000 Oct;108(4):1697-709. doi: 10.1121/1.1286812.
A combined experimental and theoretical study is presented for the feasibility of using aluminum foams with semiopen cells for sound-absorption applications. The foams are processed via negative-pressure infiltration, using a preform consisting of water-soluble spherical particles. An analytical model is developed to quantify the dependence of pore connectivity on processing parameters, including infiltration pressure, particle size, wetting angle, and surface tension of molten alloy. Normal sound-absorption coefficient and static flow resistance are measured for samples having different porosity, pore size, and pore opening. A theory is developed for idealized semiopen metallic foams, with a regular hexagonal hollow prism having one circular aperture on each of its eight surfaces as the unit cell. The theory is built upon the acoustic impedance of the circular apertures (orifices) and cylindrical cavities due to viscous effects, and the principle of electroacoustic analogy. The predicted sound-absorption coefficients are compared with those measured. To help select processing parameters for producing semiopen metallic foams with desirable sound-absorbing properties, emphasis is placed on revealing the correlation between sound absorption and morphological parameters such as pore size, pore opening, and porosity.
本文针对使用具有半开放孔的泡沫铝进行吸声应用的可行性开展了一项实验与理论相结合的研究。这些泡沫通过负压浸渗工艺制备，使用由水溶性球形颗粒组成的预制件。建立了一个分析模型，以量化孔隙连通性对包括浸渗压力、颗粒尺寸、润湿角和熔融合金表面张力在内的工艺参数的依赖性。对具有不同孔隙率、孔径和孔开口的样品测量了法向吸声系数和静态流动阻力。针对理想化的半开放金属泡沫，提出了一种理论，以具有规则六边形空心棱柱且在其八个表面上各有一个圆形孔口的结构作为单元胞。该理论基于圆形孔口（孔）和圆柱腔由于粘性效应产生的声阻抗以及电声类比原理。将预测的吸声系数与测量值进行了比较。为了帮助选择用于生产具有理想吸声性能的半开放金属泡沫的工艺参数，重点在于揭示吸声与诸如孔径、孔开口和孔隙率等形态参数之间的相关性。
