闭孔泡沫铝材料吸声性能分析

为更全面地反映闭孔泡沫铝材料的吸声降噪能力,从密度、厚度、背后空腔深度、打孔率几个方面,对闭孔泡沫铝材料的吸声性能进行研究.改变以往单纯用吸声系数的峰值表征的方法,而是用吸声系数的峰值、降噪系数、半峰宽3个指标来评价闭孔泡沫铝材料的吸声性能.通过驻波管法测试吸声系数,用Origin软件进行吸声曲线的分析,建立一次函数.结果表明:在以往研究中个别吸声系数的峰值较高的样品,整体吸声效果不佳;而一些吸声系数的峰值处于中等水平的却具有较好的整体吸声效果,因此更适合于在实际应用中用于吸声结构的设计.     

打孔提高闭孔泡沫铝吸声性能的机理分析

采用驻波管吸声系数测试仪分别测定闭孔泡沫铝板、打孔闭孔泡沫铝板、打孔铝板的吸声系数,结合共振结构吸声特性曲线,分析闭孔泡沫铝打孔后的结构特征,对吸声机理进行探讨。结果表明,打孔后闭孔泡沫铝吸声系数峰值可达0.68,高于未打孔时的0.42,也高于打孔铝板的0.45,降噪系数同样有所升高。打孔闭孔泡沫铝吸声机理主要是由于表面漫反射的干涉消声、内部微孔和裂纹造成声波的能量耗散、打孔后与背板间形成共振结构及打孔对内部孔洞的结构改变增大了吸声。     

电沉积泡沫镍的中频吸声性能

噪声污染是一个受到社会广泛关注的重要问题,因此噪声控制得到国内外的大量研究。多孔结构的吸声材料可以有效地消音降噪,探讨三维网状孔隙结构的泡沫镍的吸声性能。这种结构的泡沫镍在很多国家都已有大规模的生产,质量稳定,孔隙尺寸规格丰富。以常用作多孔电极的泡沫镍片材为研究对象,采用驻波管法测定其吸声系数。结果发现,泡沫镍片材总厚为8 mm左右的叠层试样对频率4000 Hz的入射声波显示出优良的吸声效果,吸声系数接近0.8。设置厚度为18.5 mm左右的空腔还可以大大提高叠层试样在2500和3150 Hz等较低声频下的吸声效果,吸声系数增加到0.5以上。研究还表明,通过空腔与试样两者的交替叠加,可以在2000 Hz的低频下获得良好的吸声效果,吸声系数接近0.5。因此,三维网状泡沫镍可以用作人耳敏感频段的优质吸声体。     

以高炉渣为原料制取泡沫玻璃对吸声的影响

以高炉渣为主要原料制备吸声泡沫玻璃,考察玻璃厚度、空腔、边缝以及开口气孔率对吸声性能的影响。结果表明,在低频区域,厚度、空腔深度和开口气孔率的增加都能提高吸声系数。但厚度超过150mm后对吸声系数提高意义不大。吸声系数只在500~3 000Hz频率范围内随边缝的增加而提高,其他频率范围内,吸声系数变化不大。     

孔排列及孔径对闭孔泡沫铝吸声性能的影响

使用驻波管法对不同打孔孔径和孔排列方式试样的吸声系数进行测试,通过吸声峰值、降噪系数、半峰宽3个角度来进行评价和分析。结果显示,只要打孔率相同,不同的孔排列方式的试样具有相似的吸声效果。吸声峰值随孔径增大向低频迁移;降噪系数随打孔率增大呈依次增大的趋势;孔径为1.5mm和2.5mm的试样半峰宽值远高于孔径3mm和3.5mm的试样。     

闭孔胞状泡沫铝的单向压缩力学性能和吸能能力

通过不同孔隙度闭孔胞状泡沫铝的准静态压缩试验,研究泡沫铝孔隙度对其力学性能和吸能能力的影响。闭孔胞状泡沫铝单轴压缩应力应变曲线呈现明显的3个阶段:线性变形、平台阶段、致密化阶段;在单向压缩情况下,泡沫铝的压缩强度、吸能能力随着孔隙度的增大而减小;采用Gibson-Ashby的模型分析闭孔胞状泡沫铝的压缩屈服强度,并提出泡沫铝吸能能力公式,为工程应用提供理论支持。     

一种新型泡沫铝及其表面改性

介绍了三种典型的泡沫铝制备方法,并比较了它们各自的优缺点.其中熔体吹气发泡法是一种新型的制备方法,此法生产的泡沫铝比重较轻,可以有效地节约资源,但其孔径大,降低了吸声系数.针对此项不足,采用表面复合铝纤维及高分子纳米涂层的方法,有效地加强了其吸声效果.     

泡沫铝的吸声性能及其在机床上的应用

分析了机床产生噪音的原因及噪音带来的危害,提出了机床噪音的控制方法,重点阐述了泡沫铝在机床上的吸声性能,通过分析和实验可以得出,泡沫铝作为一种吸音材质,在机床上的应用效果明显,而且不会影响机床本身的使用性能。     

钢渣基浆料黏度对多孔吸声材料结构与性能的影响

钢渣和粉煤灰等资源的高效利用是目前中国资源利用领域的研究焦点。用废弃物制备多孔吸声材料是一种具有高附加值的利用途径。以钢渣和高铝粉煤灰为原料,采用有机泡沫浸渍法制备多孔吸声材料。通过内柱体旋转法研究固相含量和增稠剂与浆料黏度的关系,以及对烧结后样品的显微形貌、吸声性能和力学性能的影响。结果表明,在低剪切速率下,随着固相含量和增稠剂含量增加,浆料的黏度逐渐上升;随着剪切速率增加,浆料黏度逐渐降低,并在达到一定剪切速率后保持稳定,但剪切应力逐渐增大。随着固相含量的增加,样品的抗压强度和抗折强度呈现上升的趋势,孔径和孔隙率则逐渐下降,且吸声性能呈现出先升高后降低的趋势。通过制备黏度低且固相含量高的浆料,可以提升样品的吸声性能和力学性能。通过制备样品的最优工艺(经1 160℃烧结1 h)制得样品的主晶相为钙长石,样品的体积密度为573.98 kg/m³、抗压强度为1.0 MPa、平均吸声系数为0.47。     

泡沫铝材料用于减振、吸声结构的初步设计

针对日益突出的噪声污染问题,以风机室的降噪处理为例,较详细地介绍了风机减振结构的设计方法、风机吸、排风口消声结构的设计方法和风机室整体的减振、隔声和消声结构的设计方法,同时给出了设计依据的基本原理。目的在于为解决工业企业的噪声污染问题提供一条新的途径,同时推动泡沫铝材料在我国的实际应用。     

Acoustic characteristics of porous bronze

Conclusions It has been shown by experiment that sound absorption by porous bronze is influenced by the specimen thickness and pore size and also by the size of the gap between the specimen and a rigid bottom. The highest values of coefficient of sound absorption (0.9–0.95) in a wide sound frequency range were attained with 8- to 10-mm-thick specimens having pores of 100- to 200-m size. By varying the size of the gap between the specimen and a rigid bottom it is possible to vary the position of the sound absorption coefficient maximum on the frequency scale without affecting its absolute value. There is good agreement between values of specific resistance to blowing through obtained as a result of acoustic and hydraulic tests, and it is therefore possible to predict the acoustic properties of porous metals from data yielded by hydraulic tests and vice versa.Translated from Poroshkovaya Metallurgiya, No. 1 (241), pp. 22–25, January, 1983.     

Acoustic characteristics of high-porosity permeable cellular materials

Conclusions High-porosity permeable cellular materials are comparable in their acoustic properties to the conventional materials (glass fiber and foam polyurethane). The key role in sound absorption by these materials is played by their structure (pore size and porosity). At a porosity of 0.85–0.9 the optimum pore size lies in the range 0.5–0.7 mm. The values of wave parameters determined in the frequency range 200–6000 Hz can be employed in calculations of HPCM sound-absorbing constructions and silencers.Translated from Poroshkovaya Metallurgiya, No. 11(287), pp. 33–36, November, 1986.     

Acoustic signaling in the black rat (Rattus rattus).

This study surveyed the vocalization repertoire of descendants of wild-trapped Rattus rattus. Sound recordings synchronized with behavioral observations were conducted in animal colony living undisturbed under seminatural conditions. Analyses of sound recordings revealed 10 distinct acoustic signals, 5 of which were in the ultrasonic frequency range. The time course and the frequency pattern of the analyzed sounds were similar to those described for R. norvegicus, and they occurred in comparable situations. A species-specific difference may be the intensity of the emitted sounds. The possible communicative function of the acoustic signals is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

闭孔金属基复合泡沫材料制备技术研究进展

闭孔金属基复合泡沫材料是一种新型多孔复合材料,主要以空心微球和基体粉末为原料,将空心微球填充到金属或合金基体中复合而成;因其具有轻质、高强、良好的阻尼、吸能、隔热、隔音及电磁屏蔽等诸多优异性能,在减震、缓冲阻尼及防撞击等相关领域具有广泛的应用价值。本文主要介绍了利用空心微球制备闭孔金属基复合泡沫材料的方法,总结了其制备过程中存在的问题,并概述了闭孔金属基复合泡沫材料的应用。     

Characteristics of aluminium metal foam for automotive applications

Closed cell aluminium foam has been examined with respect to crash protection systems, stiff and strong light weight structures and sound absorbing panels / enclosures for use in automotive systems. Monotonic compression tests revealed that the crash box made from aluminium foam-filled steel tube showed twice the energy absorption compared to empty crash box. Flexural studies on foam-filled thin walled aluminium extruded section showed higher resistance to bending (7.5 kN) against empty Al-section (5.8 kN). Differences in the mechanisms of deformation between foam filled sections and their empty counterparts were studied in compression and bend loading conditions. Acoustic behaviour was evaluated in the as-received foam and in foams post processed to increase cell interconnectivity. High sound absorption coefficients were observed in most conditions. The optimum combination of high sound absorption coefficient and frequency range occurred in a crushed foam with good cell interconnectivity.     

Fabrication of Two-Layered Aluminum Foam Having Layers with Closed-Cell and Open-Cell Pores

Two-layered aluminum foam having layers with both closed-cell and open-cell pores was fabricated using the precursor foaming process and the sintering dissolution process. It was found that a two-layered Al foam with different pore structures but similar compression properties in each layer can be obtained. This foam is expected to have a region with superior thermal insulation and a region with superior heat release properties.     

泡沫铝及其复合材料的研究进展

泡沫金属是一种由金属基体和气孔组成的新型结构功能材料,相对于实体金属材料,泡沫金属材料以牺牲了强度等力学性能为代价,获得了诸如热、声、能量吸收、轻质等优越性能,成为一种新型结构功能材料。泡沫铝是一种在铝基体中形成很多气孔的轻质多孔金属材料,同时兼有金属和气泡特征,它密度小、耐高温、防火性能强、抗腐蚀、隔音降噪、导热率低、电磁屏蔽性高、耐候性强、有过滤能力、渗透性好,具有良好的阻尼特性和电磁屏蔽能力,广泛应用在冶金、化工、航空航天、船舶、电子、汽车制造和建筑业等领域。对泡沫铝制备方法和物理性能的研究有利于提高其性能、扩大其应用领域,本文概述了泡沫铝的制备方法、物理性能及增强泡沫铝基复合材料的研究进展。